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    [Illustration: Geology of Arches National Park]

    [Illustration: BALANCED ROCK, guarding The Windows section of Arches
    National Park. Rock is Slick Rock Member of Entrada Sandstone
    resting upon crinkly bedded Dewey Bridge Member of the Entrada.
    White rock in foreground is Navajo Sandstone. La Sal Mountains on
    right skyline. (Frontispiece)]

    [Illustration: Graphic Title Page]




                        _The Geologic Story of_
                                 Arches
                             NATIONAL PARK


                            By S. W. Lohman
                              Graphics by
                             John R. Stacy

                    GEOLOGICAL SURVEY BULLETIN 1393


                UNITED STATES DEPARTMENT OF THE INTERIOR
                    ROGERS C. B. MORTON, _Secretary_

                           GEOLOGICAL SURVEY
                       V. E. McKelvey, _Director_

    [Illustration: Department of the Interior · March 3, 1949]

                 U.S. GOVERNMENT PRINTING OFFICE: 1975


  Library of Congress Cataloging in Publication Data
  Lohman, Stanley William, 1907-
  The geologic story of Arches National Park.
  (Geological Survey Bulletin 1393)
  Bibliography: p.
  Includes index.
  Supt. of Docs. no.: I 19.3:1393
  1. Geology--Utah--Arches National Park--Guide-books.
  2. Arches National Park, Utah--Guide-books.
  I. Title. II. Series: United States Geological Survey
  Bulletin 1393.
  QE75.B9 No. 1393 [QE170.A7] 557.3'08s [557.92'58]
  74-23324


 For sale by the Superintendent of Documents, U. S. Government Printing
                                 Office
                        Washington, D. C. 20402
                      Stock Number 024-001-02598-1




                                Contents


                                                                     Page
  Beginning of a monument                                               1
  Graduation to a park                                                  5
  Early history                                                         9
      Prehistoric people                                                9
      Late arrivals                                                    12
  Geographic setting                                                   18
  Deposition of the rock materials                                     20
  Bending and breaking of the rocks                                    24
  Uplift and erosion of the Plateau                                    33
  Origin and development of the arches                                 37
      Examples of arches                                               46
  How to see the park                                                  50
  A trip through the park                                              52
      Colorado River canyon                                            52
      Headquarters area                                                57
      Courthouse Towers area                                           63
      The Windows section                                              68
      Delicate Arch area                                               74
      Fiery Furnace                                                    79
      Salt Valley and Klondike Bluffs                                  82
      Devils Garden                                                    83
  Summary of geologic history                                          98
  Additional reading                                                  104
  Acknowledgments                                                     105
  Selected references                                                 105
  Index                                                               109




                                Figures


                                                                     Page
  Frontispiece. Balanced Rock.
  1. Arches National Park                                               6
  2. Rock art in Arches National Park                                  11
  3. Wolfe's Bar-DX Ranch                                              14
  4. Rock column of Arches National Park                               21
  5. Common types of rock folds                                        25
  6. Common types of rock faults                                       26
  7. Paradox basin                                                     27
  8. Geologic section across northwest end of Arches National Park     28
  9. Index map of northwestern part of Arches National Park            28
  10. Gravity anomalies over Salt Valley                               31
  11. Tilted block of rocks in Cache Valley graben                     34
  12. Jointed northeast flank of Salt Valley anticline                 36
  13. Index map                                                        38
  14. Tunnel Arch                                                      43
  15. "Baby Arch"                                                      44
  16. Broken Arch                                                      45
  17. Double Arch                                                      47
  18. Pothole Arch                                                     48
  19. Glen Canyon Group                                                53
  20. Navajo Sandstone cliffs                                          54
  21. Mouth of Salt Wash                                               55
  22. Southeast end of faulted Cache Valley anticline                  56
  23. Faulted Seven Mile-Moab Valley anticline                         58
  24. Three Penguins                                                   59
  25. Moab Valley                                                      60
  26. Faulted wall of Entrada Sandstone                                61
  27. Park Avenue                                                      62
  28. Balanced rocks on south wall of Park Avenue                      64
  29. Courthouse Towers                                                65
  30. The Three Gossips                                                66
  31. Sheep Rock                                                       66
  32. Petrified sand dunes                                             67
  33. "Hoodoos and goblins"                                            68
  34. Eye of The Whale                                                 69
  35. Intricate crossbeds in Navajo Sandstone                          70
  36. Cove Arch and Cove of Caves                                      71
  37. North Window                                                     72
  38. Looking southwestward through North Window                       73
  39. South Window                                                     74
  40. Turret Arch                                                      75
  41. Parade of Elephants                                              76
  42. Suspension foot bridge across Salt Wash                          78
  43. Delicate Arch                                                    78
  44. Fiery Furnace                                                    80
  45. Trail to Sand Dune Arch                                          81
  46. Sand Dune Arch                                                   82
  47. Tower Arch                                                       84
  48. Skyline Arch                                                     85
  49. Campground in Devils Garden                                      86
  50. View north from campground                                       87
  51. Southeastern part of Devils Garden trail                         88
  52. Pine Tree Arch                                                   89
  53. Landscape Arch                                                   91
  54. Navajo Arch                                                      92
  55. Partition Arch                                                   93
  56. Double O Arch                                                    93
  57. Dark Angel                                                       94
  58. "Indian-Head Arch"                                               95
  59. Geologic time spiral                                             96

    [Illustration: Petroglyph figure]




Beginning of a Monument


According to former Superintendent Bates Wilson (1956), Prof. Lawrence
M. Gould, of the University of Michigan, was the first to recognize the
geologic and scenic values of the Arches area in eastern Utah and to
urge its creation as a national monument. Mrs. Faun McConkie Tanner[1]
told me that Professor Gould, who had done a thesis problem in the
nearby La Sal Mountains, was first taken through the area by Marv
Turnbow, third owner of Wolfe cabin. (See p. 12.) When Professor Gould
went into ecstasy over the beautiful scenery, Turnbow replied, "I didn't
know there was anything unusual about it."

Dr. J. W. Williams, generally regarded as father of the monument, and L.
L. (Bish) Taylor, of the Moab Times-Independent, were the local leaders
in following up on Gould's suggestion and, with the help of the Moab
Lions Club, their efforts finally succeeded on April 12, 1929, when
President Herbert Hoover proclaimed Arches National Monument, then
comprising only 7 square miles.[2] It was enlarged to about 53 square
miles by President Franklin D. Roosevelt's Proclamation of November 25,
1938, and remained at nearly that size, with some boundary adjustments
on July 22, 1960, until it was enlarged to about 130 square miles by
President Lyndon B. Johnson's Proclamation of January 20, 1969.

According to Breed (1947), Harry Goulding, of Monument Valley, in a
specially equipped car, traversed the rugged sand and rocks of the
Arches region in the fall of 1936 and, thus, became the first person to
drive a car into The Windows section of Arches National Monument. Soon
after, a bulldozer followed Harry's tracks and made a passable trail.

When my family and I visited the monument in 1946, the entrance was
about 12 miles northwest of Moab on U.S. Highway 163 (then U.S. 160),
where Goulding's old tire tracks led eastward past a small sign reading
"Arches National Monument 8 miles." This primitive road crossed the
sandy, normally dry Courthouse Wash and ended in what is now called The
Windows section. At that time there was no water or ranger station, nor
were there any picnic tables or other improvements within the monument
proper, and the custodian was housed in an old barracks of the Civilian
Conservation Corps near what is now the entrance, 5 miles northwest of
Moab.

Former Custodian Russell L. Mahan reported (oral commun., May 1973) that
soon after our initial visit in 1946 a 500-gallon tank was installed
near Double Arch in The Windows section and connected to a drinking
fountain and that two picnic tables and a pit toilet were added. At that
time the only access to Salt Valley and what is now called Devils Garden
was a primitive dirt road which, according to Breed (1947, p. 175), left
old U.S. Highway 160 (now U.S. 163) 24 miles northwest of Moab, went 22
miles east, then followed Salt Valley Wash down to Wolfe cabin (fig. 1).

According to Abbey (1971), who served as a seasonal ranger beginning
about 1958, a sign had by then been erected at the crossing of
Courthouse Wash which read:

                           WARNING: QUICKSAND
                           DO NOT CROSS WASH
                         WHEN WATER IS RUNNING

The ranger station, his home for 6 months of the year, was what Abbey
described as "a little tin housetrailer." Nearby was an information
display under a "lean-to shelter." He had propane fuel for heat,
cooking, and refrigeration, and a small gasoline-engine-driven generator
for lights at night. His water came from the 500-gallon tank, which was
filled at intervals from a tank truck. At that time there were three
small dry campgrounds, each with tables, fireplaces, garbage cans, and
pit toilets. By that time an extension of the dirt road led northward to
Devils Garden, and some trails had been built and marked.

Bates Wilson became Custodian of the monument in 1949 and later became
Superintendent not only of Arches but also of the nearby new Canyonlands
National Park (Lohman, 1974) and the more distant Natural Bridges
National Monument. In the fall of 1969, Bates told me of some of his
early experiences in the undeveloped monument, including the evening
when 22 cars were marooned on the wrong (northeast) side of Courthouse
Wash after a flash flood. Bates and his "lone" ranger brought ropes,
coffee, and what food they could obtain in town after closing time,
threw a line across the swollen stream, had a tourist pull a rope
across, then took turns wading the stream with one hand on the rope and
the other balancing supplies on his shoulder. After a fire had been
built and hot coffee and food passed around, the spirits of the stranded
group rose considerably, except for one irate woman from the East, who
refused to budge from her car. Bates and his helper finally got the last
car out about 1 a.m., after the flood had subsided, and Mrs. Wilson then
supplied lodging and more food and coffee for those who needed it.

During and for sometime after World War II and the Korean War, lack of
maintenance funds and personnel had prevented improvement of the
facilities in many of our national parks and monuments, particularly in
undeveloped ones like Arches. The day was saved through the wisdom and
foresight of former Park Service Director Conrad L. Wirth, who saw the
need and desirability of putting the whole "want" list into one
attractive, marketable package. In the words of Everhart (1972, p. 36):

  Selection of a name is of course recognized as the most important
  decision in any large-scale enterprise, and here Wirth struck pure
  gold. In 1966 the Park Service would be celebrating its fiftieth
  anniversary. What a God-given target to shoot for! Why not produce a
  ten-year program, which would begin in 1956, aimed to bring every park
  up to standard by 1966--and call it Mission 66?

The ensuing well-documented and cost-estimated plan for Mission 66 was
enthusiastically backed by President Dwight D. Eisenhower and approved
and well supported by Congress to the tune of more than $1 billion
during the 10-year period. For Arches, this included a new entrance,
Park Headquarters, Visitor Center, a museum boasting a bust of founder
Dr. Williams, and modern housing for park personnel, all 5 miles
northwest of Moab. By 1958 (Pierson, 1960) a fine new paved road between
Park Headquarters and Balanced Rock (frontispiece) was completed. These
badly needed improvements were followed by the completion of the paved
road all the way to Devils Garden, the building of the modern
campground, picnic facilities, and amphitheater in the Devils Garden,
and the construction of turnouts and marked trails.

    [Illustration: Petroglyph figure]




Graduation to a Park


Arches graduated to a full-fledged national park when President Richard
M. Nixon signed a Congressional Bill on November 16, 1971. The change in
status was accompanied by boundary changes that reduced the area to
about 114 square miles. The loss of most of Dry Mesa, just east of the
present boundary (fig. 1), was offset in part by gains of new land
northwest of Devils Garden. The present (1974) boundaries, roads,
trails, and named features of the park are shown in figure 1.

The park was virtually completed at graduation time, and so far this
change in status has shown up mainly in new entrance signs, a new 1972
brochure and map, and a very informative "Guide to an Auto Tour of
Arches National Park," keyed to numbered signs at parking spaces. About
all that remain to be added are new wayside exhibits, some boundary
fences, and spur roads and trails.

    [Illustration: ARCHES NATIONAL PARK, showing location in Utah,
    boundaries, streams, highways and roads, trails, landforms,
    principal named features, and the city of Moab. The reader is
    referred to figure 7 and to road maps issued by the State or by oil
    companies for the locations of other nearby towns and features.
    Visitors also may obtain pamphlets, from the entrance station or
    from the National Park Service office in Moab, which contain
    up-to-date maps of the park and the latest available information on
    roads, trails, campsites, and picnic sites. (Fig. 1)]

Although Arches had officially become a park in November 1971, it was
not formally dedicated until May 15, 1972. The ceremony began by having
the Federal, State, and local dignitaries and other guests totaling 140
persons board the _Canyon King_, a 93-foot replica of a Mississippi
River sternwheeler (Lansford, 1972; Lohman, 1974, fig. 69), for its
maiden voyage down the Colorado River. After about half an hour, the
heavily laden boat became stuck on a sandbar, and after a 90-minute wait
the passengers were rescued by jet boats. This delayed a luncheon at the
Visitor Center put on by the Moab Lions Club. Following the luncheon,
Park Superintendent Bates Wilson made a brief welcoming address, then
introduced J. Leonard Volz, Director of the Midwest Region of the
National Park Service, who served as master of ceremonies. Speakers
included Utah Governor Calvin L. Rampton, Senator Frank E. Moss, a
representative of Senator Wallace F. Bennett, Representatives Sherman P.
Lloyd of Utah and Wayne Aspinall of Colorado, and Mitchell Melich,
Solicitor General of the Department of Interior, representing Secretary
Rogers C. B. Morton. After the speeches, a commemorative plaque, donated
by the Canyonlands Natural History Association, was unveiled by Senator
Moss and Mr. Melich.

Most of the color photographs were taken by me on 4- x 5-inch film in a
tripod-mounted press camera, using lenses of several focal lengths, but
a few were taken on 35-mm film, using lenses of various focal lengths. I
am grateful to several friends for the color photographs credited to
them in the figure captions. The black and white photographs were kindly
loaned from the Moab and Arches files of the National Park Service. The
points from which most of the photographs were taken are shown in figure
13.

    [Illustration: Petroglyph figure]




Early History


                           Prehistoric People

The Canyon lands in and south of Arches were inhabited by cliff dwellers
centuries before the first visits of the Spaniards and fur trappers.
Projectile points and other artifacts found in the nearby La Sal and
Abajo Mountains indicate occupation by aborigines during the period from
about 3000-2000 B.C. to about A.D. 1 (Hunt, Alice, 1956). The Fremont
people occupied the area around A.D. 850 or 900, and the Pueblo or
Anasazi people from about A.D. 1075 to their departure in the late 12th
century (Jennings, 1970). Most of the evidence for these early
occupations has been found in and south of Canyonlands National Park
(Lohman, 1974), but some traces of these and possibly earlier cultures
have been found also within Arches National Park.

Ross A. Maxwell (National Park Service, written commun., 1941)
investigated two caves in the Entrada Sandstone in the upper reaches of
Salt Wash that contain Anasazi ruins. He mentioned that perhaps a dozen
or more other caves should be checked for evidence of former occupation
and, also, that he found several ancient campsites littered with flint
chips and broken tools.

One cave Maxwell explored some 5 miles north of Wolfe Ranch and north of
the park is about 300 feet long and 100 to 150 feet deep. It contains
the remains of one or more ruins of a structure he thought may have
covered much of the floor. The remaining parts of walls now are only two
to four tiers of stones in height, although originally they may have
been more than one story high. Maxwell explored a second cave on the
east side of Salt Wash, about 2 miles north of Wolfe Ranch, which
contains 16 storage cists of adobe.

The faces of many older sandstone cliffs or ledges are darkened by
desert varnish--a natural pigment of iron and manganese oxides. The
prehistoric inhabitants of the Plateau learned that effective and
enduring designs, called petroglyphs, could be created simply by
chiseling or pecking through the thin dark layer to reveal the buff or
tan sandstone beneath. Most petroglyphs were created by the Anasazi, but
those showing men mounted on horses were done by Ute tribesmen after the
Spaniards brought in horses in the 1500's. The Fremont people and some
earlier people painted figures on rock faces, called pictographs, and
some of these had pecked outlines.

The so-called "Moab panel" was described by Beckwith (1934, p. 177) as a
petroglyph, but, as pointed out by Schaafsma (1971, p. 72, 73), it
comprises figures having pecked outlines and painted bodies, which
actually are combinations of petroglyphs and pictographs. This
beautifully preserved group of paintings is shown in the upper
photograph of figure 2. Mrs. Schaafsma goes on to say, concerning the
"Moab panel":

  The long tapered body, the antenna like headdresses, and the staring
  eyes are characteristic features of Barrier Canyon style figures
  elsewhere * * *. Of special interest here are the large shields held
  by certain figures. A visit to this site indicated that the shields,
  although apparently of some antiquity, have been superimposed over
  some of the Barrier Canyon figures. Whether or not this was done by
  the Barrier Canyon style artists themselves or later comers to the
  site is impossible to tell.

Although definite proof seems lacking, she suggested (written commun.,
Nov. 3, 1973) that the "'Barrier Canyon style'[3] * * * is earlier than
the work in the same region clearly attributable to the Fremont." Note
the three bullet holes in and near the right-hand shield. A ledge above
the panel that contained petroglyphs during her earlier visit had fallen
to the base of the cliff by the time my wife and I inspected the panel
in September 1973.

    [Illustration: ROCK ART IN ARCHES NATIONAL PARK. A (above), "Moab
    panel," on cliff of Wingate Sandstone above U.S. Highway 163 between
    Courthouse Wash and Colorado River, believed to be the work of
    "Barrier Canyon" style people. B (below), Petroglyphs on ledge of
    sandstone in Morrison Formation on east side of Salt Wash just north
    of Wolfe Ranch, believed to have been cut by Ute tribesmen. (Fig.
    2)]

    [Illustration: Fig. 2 B]

Mrs. Schaafsma believes the petroglyphs in the lower photograph of
figure 2 to be the work of Ute tribesmen, not only because of the
horses, but also because of the stiff-legged appearance of the mountain
sheep. Note the bullet hole above the panel.


                             Late Arrivals

Later arrivals in and near Arches National Park included first Spanish
explorers, then trappers, cattlemen, cattle rustlers and horse thieves,
followed in the present century by oil drillers, uranium hunters,
jeepsters, and tourists. Butch Cassidy, the Sundance Kid, and other
members of The Wild Bunch are known to have frequented parts of what is
now Canyonlands National Park (Baker, Pearl, 1971), but it is not
certain whether or not any of them traversed what is now Arches National
Park.

The first settler in what is now Arches National Park was a Civil War
veteran named John Wesley Wolfe, who was discharged from the Union Army
about 3 weeks before the Battle of Bull Run because he suffered from
varicose veins. In 1888 his doctor told him he had to leave Ohio for a
dryer climate or he would not live 6 months, so he took his son Fred
west and settled on a tract of 150 acres along the west bank of Salt
Wash, where his "Wolfe cabin" still stands (figs. 1, 3). From family
letters and newspaper clippings compiled by Mrs. Maxine Newell and other
members of the National Park Service (Maxine Newell, written commun.,
1971), we learn what life in the area was like:

  We have started a cattle spread on a desert homestead. We call it the
  Bar-DX Ranch. Fred and I live in a little log house on the bank of a
  creek that is sometimes dry, sometimes flooded from bank to bank with
  roaring muddy water. We are surrounded with rocks--gigantic red rock
  formations, massive arches and weird figures, the like of which youve
  [sic] never seen. The desert is a hostile, demanding country, hot in
  summer, cold in winter. The Bar-DX Ranch is a day's ride from the
  nearest store, out of the range of schools.

Although John Wolfe had promised his wife and his other children that he
would return home the first fall that his cattle sales netted enough
money, he and Fred stayed on and on, and his wife refused to go west and
join her husband and son. Eighteen years later he sent money from his
pension check to his daughter, Mrs. Flora Stanley, his son-in-law, Ed
Stanley, and his two grandchildren, Esther and Ferol, to join him and
Fred at the ranch. Their train was met at Thompson Springs (now
Thompson), Utah (fig. 7), by John Wolfe for the 30-mile ride to the
ranch by horse and wagon. Sight of the tiny log cabin with only a dirt
floor brought tears to his daughter's eyes, but her spirits rose
considerably after John Wolfe promised to build a new log cabin with a
wooden floor. But the children were enchanted with this strange country,
with the building of the new cabin, and, especially, with getting to go
rabbit hunting with Grandpa Wolfe. The Stanleys stayed at the ranch
until Esther was 10, then moved to Moab to await the arrival of their
third child, Volna.

In 1910 John Wolfe sold the Bar-DX Ranch, and the entire family moved to
Kansas. John Wolfe later moved back to Ohio, and died at Etna, Licking
County, on October 22, 1913, at the age of 84, 25 years after his doctor
had warned him to move to a dryer climate or face an early death.

Wolfe had sold his spread to Tommy Larson, who later sold it to J. Marv
Turnbow and his partners, Lester Walker and Stib Beeson. The old log
cabin gradually came to be known as the "Turnbow cabin," and this name
appeared on early maps of the area by the U.S. Geological Survey and on
early pamphlets by the National Park Service, partly because Marv
Turnbow served as a camphand in 1927 assisting in the first detailed
geologic mapping of the area (Dane, 1935, p. 4). In 1947 the ranch was
sold to Emmett Elizondo, who later sold it to the Government for
inclusion in what was then the monument.

From information supplied by Wolfe's granddaughter, Mrs. Esther Stanley
Rison, and his great-granddaughter, Mrs. Hazel Wolfe Hastler, who
visited the cabin in July 1970, the original name Wolfe cabin, or Wolfe
Ranch, has been restored, and appears on the newer maps and pamphlets.
(See fig. 1.) What remains of Wolfe's Bar-DX Ranch is shown in figure 3.

    [Illustration: WOLFE'S BAR-DX RANCH, on west bank of Salt Wash at
    start of trail to Delicate Arch. Left to right: Corral, wagon, "new"
    cabin, and root cellar. "Old" cabin, which formerly was to right of
    photograph, was washed away by a flood in 1906. (Fig. 3)]

Arches National Park is surrounded by active uranium and vanadium mines
and by many test wells for oil, gas, and potash; it is underlain by
extensive salt and potash deposits. Oil and gas are produced a few miles
to the north and east, and potash is being produced about 12 miles to
the south (Lohman, 1974).

Uranium and vanadium have been mined on the Colorado Plateau since 1898
(Dane, 1935, p. 176) and in the Yellow Cat area (also called Thompson's
area), just north of the park (fig. 1), since about 1911 (Stokes, 1952,
p. 7). The deposits in the Yellow Cat area occur in the Salt Wash
Sandstone Member of the Morrison Formation (fig. 4). According to Pete
Beroni (U.S. Atomic Energy Commission, oral commun., August 6, 1973),
some ore is still being produced in the Yellow Cat area, and the
production of vanadium ore will increase as soon as the uranium mill at
Moab is converted to also handle vanadium ore. The Corral and so-called
Shinarump mines along the southwest side of Moab Canyon just north of
Sevenmile Canyon (fig. 1) are still actively producing uranium ore from
the Moss Back Member of the Chinle Formation, according to Mr. Beroni.

The occurrences of salt and potash in and near the park and the attempts
to find oil and gas nearby are discussed in a recent report (Hite and
Lohman, 1973), and the deposits beneath Moab, Salt, and Cache Valleys
are discussed in later chapters.

In 1955 and 1956 the Pacific Northwest Pipeline, known also as the
"Scenic Inch," was constructed by the Pacific Northwest Pipeline Corp.
to transmit natural gas from wells in the San Juan Basin of northwestern
New Mexico for a total of 1,487 miles to the Pacific Northwest, with
additional pickups from gas fields in northeastern Utah, northwestern
Colorado, and southwestern Wyoming (Walters, 1956). This 26-inch
pipeline follows the general route of U.S. Highway 163 from Cortez,
Colo., past Moab to Sevenmile Canyon 10 miles northwest of Moab, where
it turns abruptly to the northeast and crosses about the middle of
Arches National Park. It crosses the park road and the flat area between
the Fiery Furnace and the southeast end of Devils Garden, but the scars
are so well healed that most visitors are unaware of its existence
unless they happen to look southwestward across Salt Valley, where the
filled excavation is still visible. The filled trench also appears in
the lower middle of figure 23.

Unlike Canyonlands National Park a few miles to the south, Arches was
not on the route of the famous early-day river expeditions of John
Wesley Powell or of most of those that followed; however, the
southeastern boundary of the park is the Colorado River, formerly the
Grand, which was traversed by the first leg of the ill-fated
Brown-Stanton expedition (Dellenbaugh, 1902, p. 343-369; Lohman, 1974).

The canyon of the Colorado River along the southeastern park boundary is
deep and beautiful and is a favorite stretch of quiet water for boaters
and floaters. Partly paved State Highway 128 on the east bank is a part
of a most scenic drive from Moab to Cisco--a small railroad town about
32 miles northeast of the eastern border of figure 1 (fig. 7). This road
has been variously called the "Moab Mail Road," the "Cisco Cutoff," the
"Dewey Road," or the "Dewey Bridge Road" after an old suspension bridge
(fig. 7) across the Colorado River at the old townsite of Dewey about 12
miles south of Cisco. During the summer this deep colorful canyon may be
viewed at night by artificial illumination. Each evening one-half hour
after sundown, an 80-passenger jet boat leaves a dock north of the
highway bridge, carries passengers several miles upstream, then floats
slowly downstream followed by a truck on the highway carrying 40,000
watts of searchlights which play back and forth on the colorful red
canyon walls, while the passengers listen to a taped discourse. The
entire trip requires about 2 hours.

The spectacular arches and red rocks of Arches and vicinity have been
used to advantage in making color movies and color TV shows. Parts of
the recent Walt Disney film "Run, Cougar, Run" were filmed beneath
Delicate Arch (fig. 43), in Professor Valley of the Colorado River just
east of the park (fig. 7), and in other sections of the canyon country.

Ever since military jet aircraft broke the sound barrier, there has been
a growing number of protests from concerned citizens, organizations, and
National Park Service officials concerning the dangers sonic booms have
posed to Indian ruins and delicate erosional forms in our national parks
and monuments, such as natural bridges, arches and windows, balanced
rocks, and natural spires or towers. Many instances of damaged ruins,
roads, erosional forms, and broken windows were reported. My wife and I
can vouch for the destructive power of such booms, for in October 1969,
while we were having breakfast at Squaw Flat Campground in The Needles
section of Canyonlands National Park, a particularly severe blast from a
low-flying jet not only violently rocked our jack-supported trailer but
broke the windshield of our car.

At Arches National Park, particular fear was felt for Landscape Arch
(fig. 53), thought to be the longest natural stone arch in the world,
and many a special round trip from headquarters involving 47 road miles
and 2 trail miles was made to check on the condition of this arch after
especially loud sonic booms were heard. Finally, in April 1972,
following a rash of newspaper and magazine articles that spread across
the nation, the Secretary of the Air Force put a virtual stop to this
danger by ruling that, except in an emergency (Moab Times-Independent,
April 12, 1972):

  Supersonic flights must not only avoid passing over national parks,
  they also may not fly near them, according to the new regulation. For
  each 1,000 feet of altitude, the pilot must allow one-half mile
  between the flight path and the park boundary. The regulation also
  prohibits supersonic flights below 30,000 feet (over land) so the high
  speed planes must allow 15 miles between the nearest park boundary and
  the flight path.

Let us hope that with the aid of this long-needed regulation and
cooperation from visitors, the arches will remain intact for many more
generations to see.

    [Illustration: Petroglyph figure]




Geographic Setting


Geologists have divided the United States into many provinces, each of
which has distinctive geologic and topographic characteristics that set
it apart from the others. One of the most intriguing and scenic of these
is the Colorado Plateaus province, referred to in this report simply as
the Colorado Plateau, or the Plateau (Hunt, C. B., 1956, fig. 1). This
province, which covers some 150,000 square miles and is not all
plateaus, as we shall see, extends from Rifle, Colo., at the northeast
to a little beyond Flagstaff, Ariz., at the southwest, and from Cedar
City, Utah, at the west nearly to Albuquerque, N. Mex., at the
southeast. Arches National Park occupies part of the Canyon Lands
Section, one of the six subdivisions of the Plateau. As the names imply,
the Canyon Lands Section of the Plateau comprises a high plateau
generally ranging in altitude from 5,000 to 7,000 feet, which has been
intricately dissected by literally thousands of canyons.

Arches National Park is drained entirely by the Colorado River, whose
deep canyon borders the park on the southeast (fig. 1). Most of the park
is drained by Salt Wash, which enters the Colorado River just southeast
of The Windows section, but the southwestern part is drained by
Courthouse Wash and Moab Canyon, whose flows join the Colorado just west
of the bridge on which U.S. Highway 163 crosses the river.

When viewed at a distance of 1 foot, the shaded relief map (fig. 1)
shows the general shape of the land surface in and near Arches National
Park to the same horizontal scale as it would appear to a person in a
spacecraft flying at a height of 250,000 feet, or about 47.5 miles. This
map was prepared from part of the reverse side of a plastic-relief
map[4] at a scale of 1:250,000 by the U.S. Army Map Service of the Moab
quadrangle, using a simple time- and money-saving method (Stacy, 1962).

    [Illustration: Petroglyph figure]




Deposition of The Rock Materials


The vivid and varied colors of the bare rocks and the fantastic buttes,
spires, columns, alcoves, caves, arches, and other erosional forms of
Arches National Park result from a fortuitous combination of geologic
and climatic circumstances and events unequalled in most other parts of
the world.

First among these events was the piling up, layer upon layer, of
thousands of feet of sedimentary rocks under a wide variety of
environments. Sedimentary rocks of the region are composed of clay,
silt, sand, and gravel carried and deposited by moving water; silt and
sand transported by wind; and some materials precipitated from water
solutions, such as limestone (calcium carbonate), dolomite (calcium and
magnesium carbonate), gypsum (calcium sulfate with some water),
anhydrite (calcium sulfate alone), common salt (sodium chloride), potash
minerals, such as potassium chloride, and a few other less common types.
Some of the beds were laid down in shallow seas that once covered the
area or in lagoons and estuaries near the sea. Other beds were deposited
by streams in inland basins or plains, a few were deposited in lakes,
and the constituents of deposits like the Navajo Sandstone, were carried
in by the wind. The character and thickness of the exposed sedimentary
rocks and the names and ages assigned to them by geologists are shown in
the rock column (fig. 4) and in the cross section (fig. 8). The history
of their deposition is summarized on pages 98-102. Figure 4 was compiled
mainly from generalized sections given by A. A. Baker (1933), Dane
(1935), McKnight (1940), and Wright, Shawe, and Lohman (1962), and, in
part, from Hite and Lohman (1973).

    [Illustration: ROCK COLUMN OF ARCHES NATIONAL PARK. Average
    thickness of units 250-1,000 feet is exaggerated two times; those
    less than 250 feet, four times. 1 foot = 0.305 meter. (Fig. 4)]


  AGE (millions of yrs ago)
    GEOLOGIC AGE
      NAME OF ROCK UNIT
            KIND OF ROCK AND HOW IT IS SCULPTURED BY EROSION
              THICKNESS (feet)
                NAMED FOR OCCURRENCE AT OR NEAR


  100
    Late Cretaceous
      Mancos Shale
            Lead-gray fossiliferous marine shale. Forms slopes.
              ?
                Mancos, Colo.
      Dakota Sandstone
            Conglomeratic sandstone, gray shale, carbonaceous shale, and
                  coal. Forms ledge.
              100
                Dakota, Nebr.
      Unconformity
    Late Jurassic
      Morrison Fm.
              700
                Morrison, Colo.
        Brushy Basin Member
            Variegated shale, some sandstone and conglomerate, petrified
                  wood, chert, and dinosaur bones. May contain some beds
                  of Burro Canyon (Early Cretaceous) age.
        Salt Wash Member
            Crossbedded white and gray conglomeratic sandstone beds and
                  lenses, locally carnotite bearing, and red and gray
                  sandy mudstone. Forms slopes.
      Unconformity
  160
      San Rafael Group
                (San Rafael Swell, Utah)
        Summerville Fm.
            Thin bedded red sandstone and shale. Some cherty limestone
                  concretions. Forms slopes.
              0-40
                Summerville Point, Utah
        Entrada Ss.
                (Entrada Point, Utah)
          Moab Member
            White, crossbedded fine-grained sandstone. Caps Slick Rock
                  Member north of Devils Garden and Fiery Furnace and on
                  Klondike Bluffs.
              0-100
                Moab, Utah
          Slick Rock Member
            Salmon-colored to pink and white fine-grained generally
                  crossbedded sandstone, containing some medium- to
                  coarse-grained sand. Generally forms cliffs or narrow
                  fins many of which contain arches or windows.
              0-240
                Slick Rock, Colo.
          Dewey Bridge Member
            Red muddy sandstone and sandy mudstone, with contorted
                  bedding. Forms easily eroded bases to arches in
                  Windows Section, hence aided in their development.
              0-175
                Dewey Bridge, Utah
      Unconformity
  190
    Jurassic and Triassic(?);
      Glen Canyon Group
        Navajo Sandstone
            Massive crossbedded buff, gray, and white fine-grained
                  sandstone, and local beds of gray limestone. Forms
                  cliffs along Colorado River, floors Windows Section.
              0-350
                Navajo Country, Four Corners (Glen Canyon, U.)
    Late Triassic(?)
        Kayenta Formation
            Lavender, gray, and white lenses of sandstone, red sandy
                  shale, and conglomerate. Contains some freshwater
                  shells. Caps and protects cliffs of Wingate Sandstone.
              0-250
                Kayenta, Ariz.
    Late Triassic
        Wingate Sandstone
            Massive, horizontally bedded and crossbedded reddish buff
                  fine-grained sandstone. Forms vertical cliffs along
                  Colorado River, Cache Valley, Salt Wash, and
                  Courthouse Wash.
              0-350
                Fort Wingate, N. Mex.
  200
      Chinle Formation
            Irregularly bedded buff to red sandstone, red mudstone,
                  limestone, and conglomerate. Lenticular sandstone and
                  conglomerate (Moss Back Member) locally at base.
                  Freshwater shells, petrified wood, reptile bones.
                  Forms slopes.
              0-700
                Chinle Valley, Ariz.
                Moss Back Ridge, Utah  Unconformity
    Middle(?) and Early Triassic
      Moenkopi Formation
            Thin-bedded brown shale, gray and brown sandstone, arkosic
                  grit, and conglomerate. Crops out on southwest side of
                  Moab Valley and in several places in Salt and Cache
                  Valleys. Forms slopes.
              0-1,300
                Moenkopi Wash, Ariz.
      Unconformity
  250
    Permian
      Cutler Formation
            Chocolate brown and red sandy shale, maroon and pinkish-gray
                  arkose and conglomerate. Lower part probably
                  equivalent in age to Rico Formation in areas to south
                  and east. Crops out in Moab Canyon west of Moab fault.
                  Forms slopes.
              0-2,500
                Cutler Creek, Colo.
    Pennsylvanian
      Hermosa Formation
        Unnamed upper member
            Gray marine fossiliferous sandy limestone, gray and
                  greenish-gray sandstone and sandy shale, and red sandy
                  shale. Exposed in ledges southwest of Moab fault in
                  highway cut west of park entrance.
              0-1,500
                Hermosa Creek, Animas River Valley, Colo.
  300
        Paradox Member
            Salt, gypsum, and anhydrite, with black and gray shale and
                  limestone. Few exposures in Salt and Cache Valleys.
                  Forms slopes.
              0-11,000
                Paradox Valley, Colo.
      Unconformity
    Pennsylvanian(?)
      Unnamed conglomerate
            Yellow sandstone with boulders of limestone and chert
                  containing Mississippian fossils. Exposed at two
                  places in Salt Valley.
              ?


Not exposed in the area but present far beneath the sedimentary cover
and exposed in several places a few miles to the northeast are examples
of the other two principal types of rocks--(1) igneous rocks, solidified
from molten rock forced into or above preexisting rocks along cracks,
joints, and faults, and (2) much older metamorphic rocks, formed from
other preexisting rock types by great heat and pressure at extreme
depths. Igneous rocks of Tertiary age (fig. 59) form the nearby La Sal
Mountains. The particles comprising the sedimentary rocks in the area
were derived by weathering and erosion of all three types of rocks in
various source areas.

Arches National Park and nearby Canyonlands National Park are both in
the heart of the Canyon Lands Section of the Plateau; therefore, it is
only reasonable to wonder why the differences in their general character
seemingly outweigh their similarities. First, let us consider the
similarities. Both parks are underlain by dominantly red sedimentary
rocks, both parks feature unusual erosional forms of sandstone, and both
contain beautiful natural arches, although the arches in Canyonlands are
restricted almost entirely to the southeastern part of The Needles
section and are in much older rocks than those in Arches.

To be sure, differences in the rocks themselves play a part in the
dissimilarity of the two parks, and these differences are of two types.
First, there are lateral changes in the character of the strata, known
to geologists as facies changes, brought about by differences in the
environment, in the type of materials, and in the mode of deposition
even within relatively short distances. Thus, during parts of the
Permian Period while sand, later to be known as the Cedar Mesa and White
Rim Sandstone Members of the Cutler Formation, was being deposited in
the southern part of Canyonlands, red mud, silt, and sand of the Cutler
were laid down farther north in Canyonlands (Lohman, 1974, fig. 9), and
similar, though somewhat coarser, beds of the Cutler were laid down at
Arches (fig. 4). Further comparisons of the rock columns in the two
parks show that while limestones of the Rico Formation were being
deposited in a shallow sea in the southern part of Canyonlands,
additional red mud, silt, and sand of the Cutler were being laid down
above sea level in areas to the northeast. The source of the coarser
materials was the ancient Uncompahgre Highland, which stood above sea
level from Late Pennsylvanian time to Late Triassic time (figs. 7, 59).
Although wider and longer, it occupied about the same position as the
present Uncompahgre Plateau between Grand Junction and Gateway, Colo.
Streams eroded the hard igneous and metamorphic rocks from this ancient
landmass and dumped the material into basins to the northeast and
southwest. The basin to the southwest, now called the Paradox basin
(after Paradox Valley, Colo.), at intervals contained shallow seas and
lagoons, which I will discuss later.

Comparison of the rock columns for the two parks also reveals other
differences. Both parks contain exposures of rocks as old as the
Pennsylvanian Paradox Member of the Hermosa Formation. However, only in
the Horseshoe Canyon Detached Unit of Canyonlands are rocks as young as
the Jurassic Entrada Sandstone, whereas all the spectacular natural
arches that make Arches famous were formed in the Entrada Sandstone, and
Arches also contains several younger formations of Jurassic and
Cretaceous age (fig. 4).

A commonly asked question is "Why are most of the rocks so red,
particularly those in which the arches were formed?" This can be
answered with one word--iron, the same pigment used in rouge and in
paint for barns and boxcars. Various oxides of iron, some including
water, produce not only brick red but also pink, salmon, brown, buff,
yellow, and even green or bluish green. This does not imply that the
rocks could be considered as sources of iron ore, for the merest trace,
generally only 1 to 3 percent, is enough to produce even the darkest
shades of red. The white or nearly white Navajo Sandstone and the Moab
Member of the Entrada Sandstone contain little or no iron.

As pointed out by Stokes (1970, p. 3), microscopic examination of the
colored grains of quartz or other minerals shows the pigment to be
merely a thin coating on and between white or colorless particles. Sand
or silt weathered from such rocks soon loses its color by the scouring
action of wind or water, so that most of the sand dunes and sand bars
are white or nearly so.




                   Bending And Breaking of The Rocks


Perhaps the greatest geologic contrast between these two closely
adjacent parks lies in their different geologic structure--the kind and
amount of bending and breaking of the once nearly flat lying strata.
Consolidated rocks, particularly brittle types, are subject to two types
of fracturing by Earth forces. Joints are fractures along which no
movement has taken place. Faults are fractures along which there has
been displacement of the two sides relative to one another (fig. 6). As
noted in the report on Canyonlands National Park (Lohman, 1974), the
strata there, particularly along the valley of the Green River, are
virtually flat lying or have only very gentle dips. Along the Colorado
River above the confluence with the Green, however, the slightly dipping
strata are interrupted by several gentle anticlinal and synclinal folds
(fig. 5) and by at least one fault (fig. 6). The largest of these
folds--the Cane Creek anticline, which crosses the Colorado River north
of Canyonlands--has yielded oil in the past and is now yielding potash
by solution mining of salt beds in the Paradox Member of the Hermosa
Formation.

    [Illustration: COMMON TYPES OF ROCK FOLDS. Top, Anticline, or
    upfold; closed anticlines are called domes. Bottom, Syncline, or
    downfold; closed synclines are called basins. From Hansen (1969, p.
    31, 108). (Fig. 5)]

In strong contrast to Canyonlands, Arches National Park contains three
northwesterly trending major folds and is bordered on the southwest by a
fourth. The largest and most important are the collapsed Salt Valley and
Cache Valley anticlines, which separate the two most scenic groups of
arches and other erosional forms--Eagle Park, Devils Garden, Fiery
Furnace, and Delicate Arch on the northeast, and Klondike Bluffs,
Herdina Park, and The Windows section on the southwest. Farther
southwest is the Courthouse syncline, containing the attractive group of
erosional forms called Courthouse Towers (fig. 1). Finally, near the
southwest edge of the park, is the Seven Mile-Moab Valley anticline
(also known as the Moab-Spanish Valley anticline), whose southwest limb
is cut off by the Moab fault (figs. 7, 23). The folds just named and the
sharply contrasting geologic structures of the two parks are well shown
on sheet 2 of the geologic map of the Moab quadrangle (Williams, 1964),
and the geologic formations are shown in color on sheet 1.

    [Illustration: COMMON TYPES OF FAULTS. Top, Normal, or gravity
    fault, resulting from tension in and lengthening of the Earth's
    crust. Bottom, reverse fault, resulting from compression in and
    shortening of the Earth's crust. Low-angle reverse faults generally
    are called overthrusts or overthrust faults. In both types, note
    amount of displacement and repetition of strata. Displacements may
    range from a few inches or feet to many thousands of feet. From
    Hansen (1969, p. 116). (Fig. 6)]

    [Illustration: PARADOX BASIN, in southeastern Utah and southwestern
    Colorado, showing the extent of common salt and major potash
    deposits in the Paradox Member of the Hermosa Formation, and the
    salt anticlines. Adapted from Hite (1972, fig. 1B). (Fig. 7)]

    [Illustration: GEOLOGIC SECTION ACROSS NORTHWEST END OF ARCHES
    NATIONAL PARK, showing strata beneath Courthouse syncline and Salt
    Valley anticline. For line of section, see figure 9. Caprock
    consists of gypsum and shale, from which common salt has been
    leached by ground water, covered by alluvium. Heavy slanted lines
    near crest of anticline are faults. Adapted from Hite and Lohman
    (1973, fig. 13). (Fig. 8)]

    [Illustration: INDEX MAP OF NORTHWESTERN PART OF ARCHES NATIONAL
    PARK, showing axes of Courthouse syncline and Salt Valley anticline,
    line of section _A_-_A_' in figure 8 and line of section _B_-_B_' in
    figure 10. Open circles along line of section are sites of test
    wells for oil, gas, or potash. Adapted from Hite and Lohman (1973,
    fig. 12). (Fig. 9)]

Arches National Park and most of nearby Canyonlands National Park lie
within what geologists have termed the "Paradox basin," which contains a
remarkable assemblage of sediments called the Paradox Member of the
Hermosa Formation. These deposits were laid down in shallow seas and
lagoons during Middle Pennsylvanian time, roughly 300 million years ago
(fig. 59). As indicated in figure 4, the Paradox Member contains, in
addition to shale and limestone, minerals deposited by the evaporation
and concentration of sea water--common salt, gypsum, anhydrite, and
potash salts. For this reason such deposits are collectively called
evaporites. Figure 7 also shows that the northeastern part of the
Paradox basin, which is the deepest part, contains a series of partly
alined anticlines which have cores of salt and, hence, are called salt
anticlines. As might be expected, roughly alined synclines intervene
between the anticlines, but are not shown because of space limitations.
According to Cater (1970, p. 50): "The salt anticlines of Utah and
Colorado are unique in North America both in structure and in mode of
development." To this may be added that they also are relatively rare in
the world.

A section across the Salt Valley anticline and the Courthouse syncline
in the northwestern part of the park is shown in figure 8, and the axes
of these structures are shown in figure 9.

Normally, a series of roughly parallel northwestward-trending folds
would result from shortening of a segment of the Earth's crust by
compressive forces from the northeast and the southwest, but such does
not seem to be the origin of these folds. The folds occur in a
relatively narrow belt along the northeastern part of the Paradox basin,
the deepest part, which was broken by a series of northwesterly trending
normal faults (fig. 6) that cut the deep-lying Precambrian and older
Paleozoic rocks (fig. 8) prior to the deposition of the salt-bearing
Paradox Member of the Hermosa Formation. Movement along these faults
continued intermittently during and after deposition of the Paradox,
however, and resulted in the formation of a series of northwesterly
trending ridges and troughs. Following Paradox time, normal sediments
derived from a rising landmass to the northeast began to fill the basin.
These sediments accumulated most rapidly and to greater thicknesses in
the fault-derived troughs. Salt differs from normal sediments in two
properties critical to the development of salt anticlines: first, salt
is considerably lighter (fig. 10), and, second, salt under pressure will
flow slowly by plastic deformation, much like ice in a glacier flows
slowly downstream. Thus, salt in the troughs underlying the thicker and
heavier masses of sediments was squeezed into the adjoining ridges,
causing them to rise. Once started, this process tended to be
self-perpetuating, as the flow of salt from beneath the thick masses of
sediments in the troughs made room for the accumulation of still greater
thicknesses of normal sediments. Consequently, the troughs receiving
most of the sediments began to form downfolds, or synclines, and the
ridges receiving little or no normal sediments began to form huge salt
rolls that later were to become the cores of the salt anticlines when
finally the ridges too were buried by sediments. Thus, the cross section
(fig. 8) shows about 12,000 feet of the Paradox Member beneath the crest
of the Salt Valley anticline and only about 2,000 feet beneath the
Courthouse syncline. Near the middle of these structures farther to the
southeast, all the Paradox Member has been squeezed out from beneath the
bordering synclines.

    [Illustration: GRAVITY ANOMALIES OVER SALT VALLEY, along line _B-B'_
    shown in figure 9, and relative densities and shapes of rock bodies
    beneath. Densities are in grams per cubic centimeter. Gravity values
    are in milligals, as shown. The standard acceleration of gravity is
    980.665 centimeters per second per second; 1 gal is equal to 1
    centimeter per second per second, and 1 milligal is one thousandth
    of a gal. Modified from Case and Joesting (1972, fig. 2). (Fig. 10)]

The general shape of the Salt Valley anticline is shown also by
cross-section _B-B'_ (fig. 10), taken along the northeast-southwest line
_B-B'_ in figure 9, which is based upon so-called gravity anomalies over
Salt Valley. The lighter Paradox Member, having an average density of
2.20, has a lower gravitational attraction than the heavier rocks on
each side, which have an average density of 2.55.

By this time you are doubtless wondering why prominent upfolds of the
rocks, such as the Salt Valley anticline and associated Cache Valley
anticline and the Seven Mile-Moab Valley anticline, now underlie
relatively deep valleys bordered by prominent ridges. The formation of
these valleys was not simple and involved many steps extending over a
considerable amount of geologic time, as portrayed by Cater (1970, fig.
13; 1972, fig. 4). For a part of the story, let us reexamine the cross
section (fig. 8); the rest of the story will be told in the section on
"Uplift and Erosion."

Figure 8 shows that the unnamed upper member of the Hermosa Formation
and the overlying Cutler and Moenkopi Formations are thickest beneath
the Courthouse syncline but wedge out against the flanks of the
anticline. Although the Chinle Formation and younger rocks appear to
extend across the fold, and may have extended across this part of the
fold, in Colorado all rocks older than the Jurassic Morrison wedge out
against the flanks of the salt anticlines (Cater, 1970, p. 35) and also
in the widest part of the Salt Valley anticline southwest of the section
in figure 8. The salt anticlines were uplifted in a series of pulses so
that some formations either were not deposited over the rising
structures or were removed by erosion before deposition of the next
younger unit. By Morrison time the supply of salt beneath the synclines
seems to have become used up; hence, the anticline stopped rising, and
the Morrison and younger formations were deposited across the
structures. Thus, in figure 4, the minimum thickness of all units older
than the Morrison is given as zero. Figure 4 shows the marine Mancos
Shale to be the youngest rock unit exposed in the park, but the
Mesaverde Group of Late Cretaceous age and possibly the early Tertiary
(fig. 59) Wasatch Formation may have been deposited and later removed by
erosion.




                   Uplift And Erosion of The Plateau


Next among the main events leading to the formation of landforms in the
park was the raising and additional buckling and breaking of the Plateau
by Earth forces partly during the Late Cretaceous but mainly during the
early Tertiary. After uplift and deformation, the Plateau was vigorously
attacked by various forces of erosion, and the rock materials pried
loose or dissolved were eventually carted away to the Gulf of California
by the ancestral Colorado River. Some idea of the enormous volume of
rock thus removed is apparent when one looks down some 2,000 feet to the
river from any of the high overlooks farther south, such as Dead Horse
Point (Lohman, 1974, fig. 15). Not so apparent, however, is the fact
that younger Mesozoic and Tertiary rocks more than 1 mile thick once
overlaid this high plateau but have been swept away by erosion. In all,
the river has carried thousands of cubic miles of sediment to the sea
and is still actively at work on this gigantic earth-moving project. In
an earlier report (Lohman, 1965, p. 42) I estimated that the rate of
removal may have been as great as about 3 cubic miles each century. For
a few years the bulk of the sediment was dumped into Lake Mead, but now
Lake Powell is getting much of it. When these and other reservoirs
ultimately become filled with sediment--for reservoirs and lakes are but
temporary things--the Gulf of California will again become the burial
ground.

According to Cater (1970, p. 65-67), who made an intensive study of the
salt anticlines, collapse of their crests seemingly occurred in two
stages--the first stage following Late Cretaceous folding; the second
following uplift of the Plateau later in the Tertiary. Solution and
removal of salt by ground water played the leading role in the ultimate
collapse.

    [Illustration: TILTED BLOCK OF ROCKS IN CACHE VALLEY GRABEN, viewed
    to the east toward Cache Valley from point on gravelled side road to
    Wolfe's cabin, about half a mile east of paved road. Steep slope on
    left composed of Jurassic Morrison Formation, hogback on top formed
    by Dakota Sandstone of Late Cretaceous age, and gentle slopes to
    right composed of the Mancos Shale of Late Cretaceous age. (Fig.
    11)]

As shown by Dane (1935, pl. 1, p. 121-126), collapse of the Salt Valley
and Cache Valley anticlines was accompanied by considerable faulting and
jointing, particularly along their northeast sides; by the upward
intrusion of two large areas of the Paradox Member of the Hermosa
Formation, one just northwest of the park and one in the middle of Salt
Valley south of the campground; and by two downdropped masses of rock
known to geologists as grabens (pronounced gräbens)--one just northwest
of the park and one called the Cache Valley graben, which extends both
east and west from Salt Wash. The Cache Valley graben has preserved from
erosion the youngest rock formations in the park, as shown in figure 11.

The remarkable jointing of the rocks on the northeast limb of the Salt
Valley anticline is shown in figure 12. All the arches in this section
of the park were eroded through thin fins of the Slick Rock Member of
the Entrada Sandstone, and some, like Broken Arch, figure 16, are capped
by the Moab Member.

Differences in the composition, hardness, arrangement, and thickness of
the rock layers determine their ability to withstand the forces of
fracturing and erosion and, hence, whether they tend to form cliffs,
ledges, fins, or slopes. Most of the cliff- or ledge-forming rocks are
sandstones consisting of sand deposited by wind or water and later
cemented together by silica (SiO_{2}), calcium carbonate (CaCO_{3}), or
one of the iron oxides (such as Fe_{2}O_{3}), but some hard, resistant
ledges are made of limestone (calcium carbonate). The rock column (fig.
4) shows in general how these rock formations are sculptured by erosion
and how they protect underlying layers from more rapid erosion. The
nearly vertical cliffs along the lower reaches of Salt and Courthouse
Washes and the Colorado River canyon upstream from Moab consist of the
well-cemented Wingate Sandstone protected above by the even harder
sandstones of the Kayenta Formation. (See figs. 21, 22.) To borrow from
an earlier report of mine (Lohman, 1965, p. 17), "Vertical cliffs and
shafts of the Wingate Sandstone endure only where the top of the
formation is capped by beds of the next younger rock unit--the Kayenta
Formation. The Kayenta is much more resistant than the Wingate, so even
a few feet of the Kayenta * * * protect the rock beneath." In some
places, as shown in figures 19 and 20, the overlying Navajo Sandstone
makes up the topmost unit of the cliff.

    [Illustration: JOINTED NORTHEAST FLANK OF SALT VALLEY ANTICLINE,
    viewed westward from an airplane. Light-colored wedge in middle
    background is Salt Valley bordered on extreme left by Klondike
    Bluffs. Dark-colored fins and pinnacles on left, of Slick Rock
    Member of the Entrada Sandstone, form Devils Garden. Sharp pinnacle
    above valley is the Dark Angel. (See fig. 57.) White bands of
    sandstone extending to foreground are composed of Moab Member of the
    Entrada. Note vegetation in the joints. Photograph by National Park
    Service. (Fig. 12)]

Last but far from least among the factors responsible for the grandeur
of Arches National Park and the Plateau in general is the desert
climate, which allows one to see virtually every foot of the vividly
colored naked rocks, and which has made possible the creation and
preservation of such a wide variety of fantastic sculptures. A wetter
climate would have produced a far different, smoother landscape in which
most of the rocks and land forms would have been hidden by vegetation.
On the Plateau the vegetation grows mainly on the high mesas and the
narrow flood plains bordering the rivers, but scanty vegetation also
occurs on the gentle slopes or flats.

The combination of layers of sediments of different composition,
hardness and thickness, the bending and breaking of the rocks, and the
desert climate, has produced steep slopes having many cliffs, ledges,
and fins with generally sharp to angular edges, rather than the subdued
rounded forms of more humid regions.




                  Origin And Development of The Arches


Among the questions commonly asked by visitors are, "How do arches
form?", "Why are some openings called windows, others arches?", "What is
the difference, if any, between arches or windows and natural bridges,
such as those at Natural Bridges National Monument?", and "How many
arches are there in Arches National Park?" Before taking up the origin
and development of arches, I shall attempt to explain the differences
between the three types of natural rock openings named above and comment
upon the number of arches.

    [Illustration: INDEX MAP, showing localities where most of the
    photographs were taken. Arrows point to distant views. Numbers refer
    to figure numbers. (Fig. 13)]

I believe most geologists and geographers are in general agreement with
Cleland (1910, p. 314) that "a 'natural bridge' is a natural stone arch
that spans a valley of erosion. A 'natural arch' is a similar structure
which, however, does not span an erosion valley." According to this
definition, Natural Bridges National Monument includes three true
bridges, whereas all the larger rock openings in Arches National Park
with which I am familiar are properly termed "arches," but some are
called windows. If we were to distinguish between arches and windows, we
might say that arches occur at or near the base of a rock wall, as do
the doors of a house or building, whereas windows are found well above
ground level. This distinction was not followed in naming the rock
openings in the park, however; for example, Tunnel Arch (fig. 14) is
considerably higher above the ground than North Window (figs. 37, 38) or
South Window (fig. 39).

As to the number of arches in the park, I might begin by saying that
there is no universal agreement as to how large a rock opening must be
to qualify as an arch. The pamphlet formerly handed to visitors entering
the park proclaimed that "Nearly 90 arches have been discovered, and
others are probably hidden away in remote and rugged parts of the area,"
but the average visitor probably sees less than a third of this number.

David May, Assistant Chief of Interpretation and Resource Management,
Moab office of National Park Service (oral commun., Oct. 1973), believes
that if only those in the park having a minimum dimension of 10 feet in
any one direction were considered to be arches, the number would boil
down to about 56 or 57. The most complete count of arches and other
openings in all of southeastern Utah was made by Dale J. Stevens,
Professor of Geography at Brigham Young University, during the period
February through April 1973. He considered those with openings of 3 feet
or larger and found more than 300 in southeastern Utah, of which 124 are
in Arches National Park, although he stated that several areas of the
park were not intensively searched because of time limitations (written
commun., July and Sept. 1973). The 124 arches and openings are
distributed among the several named areas of the park, as follows:
Courthouse Towers, 13; Herdina Park, 11; The Windows section, 25;
Delicate Arch area, 3; Fiery Furnace, 19; Devils Garden, 25; upper
Devils Garden (northwest of Devils Garden), 14; Eagle Park, 2; and
Klondike Bluffs, 12.

Professor Stevens generally used a range finder or a steel tape to
measure the width and height of the openings and the width and thickness
of the spans, but estimated a few of the dimensions. In the text
descriptions of arches or captions of figures that follow, I am
including all or part of these measurements, without further
acknowledgment.

All the arches in the park were formed in the Entrada Sandstone, mainly
in the Slick Rock Member but partly in the Slick Rock and Dewey Bridge
Members, and a few in the Slick Rock Member occur not far beneath the
base of the overlying Moab Member. The sandstone of the three members is
composed mainly of quartz sand cemented together by calcium carbonate
(CaCO_{3}), which also forms the mineral calcite and the rock known as
limestone, but the Dewey Bridge Member also contains beds of sandy
mudstone. Limestone and calcite are soluble in acid, even in weak acid
such as carbonic acid, HHCO_{3}, also written H_{2}CO_{3}, formed by the
solution of carbon dioxide (CO_{2}) in water. Ground water, found
everywhere in rock openings at different depths beneath the land
surface, contains dissolved carbon dioxide derived from decaying organic
matter in soil, from the atmosphere, and from other sources. Even
rainwater and snow contain a little carbon dioxide absorbed from the
atmosphere--enough to dissolve small amounts of limestone or of calcite
cement from sandstone. The calcite cement in the Entrada and in many
other sandstones is unevenly distributed, however, so that all the
cement is removed first from places that contain the least amounts, and,
once the cement is dissolved away, the loose sand is carried away by
gravity, wind, or water.

Both nearly flat but slightly irregular beds of sandstone and relatively
thin walls or fins of sandstone are prime targets for this differential
erosion. Potholes, as shown in figure 18_A_, may be formed in relatively
flat beds by the dissolving action of repeated accumulations of
rainwater or snowmelt, even in arid regions like the Plateau.

Relatively thin walls, or fins as they are called in parts of the
Plateau including Arches, are targets for the formation of alcoves and
caves by solution of cement and removal of sand by gravity, wind, and
water, aided by the prying action of frost in joints, bedding planes, or
other openings. Once a breakthrough of a wall or fin occurs, weakened
chunks from the ceiling tend to fall, and natural arches of various
shapes and sizes are produced. Arches form the strongest shapes for
supporting overlying rock loads, as the rock in the arch is compressed
toward each abutment by the heavy loads. Blocks of compressed rock
beneath a relatively flat ceiling tend to be dislodged also by expansion
due to release of pent-up pressure, until a strong self-supporting arch
is formed. Release of pent-up pressure in rock walls may help also in
initiating the formation of alcoves or caves in cliff faces. Man,
including the ancient Greeks, Romans, Egyptians, and others, has long
made use of arches in building bridges, aqueducts, temples, cathedrals,
and other enduring edifices.

As vividly shown in figure 12, the Entrada Sandstone on the northeast
flank of the Salt Valley anticline has been broken by Earth forces into
thin slabs mostly 10 to 20 feet thick between nearly parallel joints,
but, as will be noted in the descriptions of individual arches, some
rock walls are only 1 or 2 feet thick, whereas others are 50 feet thick
or more. Some weak or thin slabs have weathered away, leaving the
stronger or thicker ones as towering fins, particularly in the Fiery
Furnace and Devils Garden areas. Jointing on a less spectacular scale
also has broken the Entrada in areas south of Salt Valley, leaving walls
or fins of rock.

    [Illustration: TUNNEL ARCH, reached by short trail north of main
    trail through Devils Garden. Opening is 26-1/2 feet wide and 22 feet
    high; span is about 14 feet thick. (Fig. 14)]

Although all the arches in the park were carved from the Entrada
Sandstone, slight differences in their mode of origin or placement
within the Entrada allow them to be grouped into three classes: (1)
vertical arches formed in the Slick Rock Member alone or in the Slick
Rock and Moab Members, (2) vertical arches formed mainly in the Slick
Rock Member but partly in, and with the aid of, the incompetent
underlying Dewey Bridge Member, and (3) horizontal arches, or so-called
pothole arches, formed from the union of a vertical pothole and a
horizontal cave. Hereinafter, the three members will be referred to
alone, without reference to the Entrada.

    [Illustration: "BABY ARCH," just southwest of Sheep Rock in
    Courthouse Towers area. For details, see text. (Fig. 15)]

Before giving examples of arches in each of the three classes, it is
appropriate to remark that the arches and other erosion forms in the
park represent but a fleeting instant in geologic time. Many of the
pinnacles or piles of rock may be the broken remains of former arches,
and many of the arches we see may be gone tomorrow, next year, or a few
hundreds of years and, certainly, before many thousands of years. On the
other hand, many new arches will form by the processes described above
as the geologic clock ticks on.

    [Illustration: BROKEN ARCH, reached by a 1/2-mile trail leading
    northward across field that separates Fiery Furnace from Devils
    Garden. White thin-bedded unit at top is the Moab Member, which
    rests upon the massive salmon-colored Slick Rock Member. Opening is
    59 feet wide and 43 feet high. (Fig. 16)]


                           Examples of Arches

Tunnel Arch (fig. 14) is a good example of an arch eroded entirely
within the massive Slick Rock Member. Just southwest of Sheep Rock (fig.
31) is an unnamed opening in the lower part of the Slick Rock Member
which I call "Baby Arch," because it is one of the newest ones visible
from the park road (fig. 15). It is only 25-1/2 feet wide and 14 feet
high and penetrates a wall 14 feet thick. Note that the breakthrough
probably began along the prominent recessed bedding plane at the base of
the arch. Its youthfulness is also indicated by the sharp, angular
breaks in the ceiling and by the pile of freshly fallen rocks. Some
visitors have asked park personnel why they have not cleared away such
debris! Despite its youthfulness, the ceiling has already taken on the
shape of an arch.

Broken Arch (fig. 16) was formed near the top of the Slick Rock Member
and is strengthened and protected by the more resistant overlying Moab
Member, which forms the upper half of the span. The crest is only 6 feet
thick at the thinnest point and is not broken as the name seems to
imply.

Double Arch (fig. 17), "one" of the most beautiful in the park, is in
The Windows section near the east end of the road. The southeast arch,
which is 160 feet wide and 105 feet high, is the second largest in the
park, but the west arch measures only 60 feet wide and 61 feet high. In
common with most arches in The Windows section, these two arches of the
Slick Rock Member rest upon bases of the weak, easily eroded Dewey
Bridge Member. More rapid erosion of the Dewey Bridge undercut the
arches and hastened their development.

    [Illustration: DOUBLE ARCH, in The Windows section. (Fig. 17)]

    [Illustration: PROBABLE STEPS IN FORMATION OF POTHOLE ARCH. _A_,
    Original pothole probably formed in relatively level bed of
    sandstone, such as this one, which is in an older rock unit--the
    White Rim Sandstone Member of the Cutler Formation, a unit not
    present in Arches. This pothole, which contains 4 feet of water, is
    in nearby Canyonlands National Park (Lohman, 1974, fig. 17), just
    north of the edge of the White Rim, about 4-1/2 miles north of the
    confluence of the Green and Colorado Rivers. Photograph by E. N.
    Hinrichs. _B_, Pothole is being deepened by solution while cliff is
    receding toward pothole by weathering. _C_, As erosion continues,
    pothole and cave in cliff face are growing deeper. _D_, Pothole Arch
    formed by union of vertical pothole and horizontal cave. _E_,
    Telephoto view of Pothole Arch from park road near stop 14. Visible
    span is 90 feet across and 30 feet high. (Fig. 18)]

    [Illustration: Fig. 18 B]

    [Illustration: Fig. 18 C]

    [Illustration: Fig. 18 D]

    [Illustration: Fig. 18 E]

The cause of the wavy bedding in the Dewey Bridge Member, as shown in
figure 17 but as better shown in the frontispiece, is not known for sure
but generally is regarded to be the result of irregular slumping during
or just after deposition of the sediments in a body of water, caused by
the weight of overlying sediments.

The last example I shall take up is Pothole Arch (fig. 18), which
differs from all the other examples in that this arch is roughly
horizontal rather than vertical. Most park visitors, including me, were
not aware of this interesting feature until after publication of the
pamphlet "The Guide to an Auto Tour of Arches National Park," which, as
previously noted, may be purchased at the Visitor Center. Pothole Arch
caps a ridge high above the road half a mile northwest of Garden of
Eden, so only those who happened to look up at the right place were
aware of its existence.

A different mode of origin than that given in the caption for figure 18
is depicted on a poster in the Visitor Center, which shows the pothole
being formed by a waterfall having an apparent flow rate of several
cubic feet per second. Potholes can be formed in this manner in places
where sufficient streamflow is available, either continuously or
following rainstorms, but I believe the process depicted in figure 18 is
a more likely mode of origin for Pothole Arch.




                          How to See the Park


As aptly stated on a poster in the Visitor Center, how to see the park
depends in part upon the question "How long can you stay?" Inasmuch as
the park entrance and Visitor Center are beside a through U.S. Highway
(163), many motorists first become aware of the park's existence from
the entrance sign, and some take time for at least a quick visit, such
as a round trip to The Windows section, which can be made in an hour or
so.

For those who have or take more time and are able to walk at least short
distances, a visit of 1 or 2 days is a very rewarding experience.
Others, particularly avid shutterbugs and those with camping gear,
profitably spend from several days to a week or more and hike all or
most of the trails.

Regardless of how long you plan to spend, I urge at least a brief stop
at the Visitor Center, where excellent displays and a narrated slide
show help materially in conveying just what the park has to offer. At
the counter you can purchase a copy of "The Guide to an Auto Tour of
Arches National Park," which explains the views from each of 25 numbered
stops along the park road, as well as other reports describing arches or
other parks and monuments.

The park is open the year round, but, like most high deserts, it gets
rather hot in the summer and cold enough in the winter for occasional
snows and is sometimes closed temporarily because of heavy snowfall. The
weather generally is ideal during the spring and fall. Even though
summer daytime temperatures may exceed 100°F (37.8°C) and slow down
hikers, the nights are cool enough for comfortable sleeping beneath
ample covers.

Before beginning our trip through the park proper, let us consider a
beautiful part many people fail to realize actually belongs to the
park--the Colorado River canyon forming the southeastern boundary.

    [Illustration: Petroglyph figure]




A Trip Through The Park


                         Colorado River Canyon

The southeastern boundary of the park for about 11 miles is the Colorado
River, from the bridge on which U.S. Highway 163 crosses the river to a
point upstream about half a mile below the mouth of Salt Wash.
Illuminated night float trips down part of this reach are run during the
summer, as noted on p. 16. Partly paved State Highway 128 follows the
southeast side of the river for about 30 miles to Dewey Bridge, then
goes northward about 15 miles to Cisco, where it connects with Highway
I-70.

The rocks of the Glen Canyon Group form the southernmost corner of the
park, as shown in figure 19. About 2 miles northeast of the bridge, we
cross the axis of the Courthouse syncline (fig. 9), which brings the
Navajo Sandstone down nearly to river level, as shown in figure 20. The
underlying Kayenta Formation is largely hidden by vegetation and
alluvial deposits in this view.

    [Illustration: GLEN CANYON GROUP, forming southernmost point of
    park, as viewed across the Colorado River from State Highway 128
    half a mile above Moab bridge carrying U.S. Highway 163. Massive
    sandstone forming about the lower third of cliff is the Wingate
    Sandstone, darker thin-bedded sandstones and mudstones forming
    middle section of cliff comprise the Kayenta Formation, upper cliff
    is the lower part of the Navajo Sandstone. Note that the saltcedar
    (tamarisk), which lines both banks of the river, is in full bloom.
    (Fig. 19)]

    [Illustration: NAVAJO SANDSTONE CLIFFS, bordering west bank of
    Colorado River in Courthouse syncline, from State Highway 128 about
    2 miles above the Moab bridge. Note rounded domes at top of cliff.
    (Fig. 20)]

    [Illustration: MOUTH OF SALT WASH, viewed across Colorado River from
    point on State Highway 128, 11 miles above Moab bridge. Dark cliffs
    on upper right and left are of Wingate Sandstone capped by thin
    protective cover of resistant sandstone beds of the Kayenta
    Formation. In background Wingate is overlain by entire Kayenta
    Formation and lower part of the Navajo Sandstone. Wingate is
    underlain to river level by weathered slope of the Chinle Formation.
    Water in Salt Wash is largely backwater from the bankfull river;
    actual flow in wash generally is much less but at times reaches
    flood proportions. (Fig. 21)]

About 11 miles above the Moab bridge is the mouth of Salt Wash (fig. 1),
as viewed from State Highway 128. (See fig. 21.) Seventeen miles above
the bridge (east of area shown in fig. 1), we get an excellent view of
the southeast end of the highly faulted Cache Valley anticline, as shown
in figure 22. The background shown in the photograph formerly was the
easternmost part of the former monument, but when the monument graduated
to a park on November 16, 1971, this part of Cache Valley along with
most of Dry Mesa was withdrawn from the park and put under the
supervision of the Bureau of Land Management, also a part of the
Department of the Interior.

    [Illustration: SOUTHEAST END OF FAULTED CACHE VALLEY ANTICLINE,
    viewed northwestward across Colorado River from a point on State
    Highway 128, 17 miles above Moab bridge. High cliff of Wingate
    Sandstone on left is capped by thin protective layer of the Kayenta
    Formation. About upper third of slope below base of cliff is the
    Chinle Formation, below which is the Moenkopi Formation extending to
    high-water level. Note bent and broken beds on right. (Fig. 22)]

As noted on page 16, part of "Run, Cougar, Run" was filmed just upstream
from the irrigated field in the foreground of figure 22, in a wide part
of the valley called Professor Valley (fig. 7). This valley and the
Richardson Amphitheater on the southeast side of the river were named
after a Professor Richardson who settled in the area in the 1880's. The
long abandoned townsite of Richardson was 1-1/4 miles due east from the
point from which figure 22 was taken.


                           Headquarters Area

The junction of the park road with U.S. Highway 163 is shown at the
lower left of figure 23, and the entrance station, Visitor Center,
parking lot, and several buildings are seen at the lower right. Several
residences for park personnel and other buildings are shown in figure
25. As shown in the lower part of figure 23, the geology at the park
entrance is rather complex, as the park boundary here is partly along
the Moab fault and partly along a branch fault--both in the Seven
Mile-Moab Valley anticline (fig. 7). The Moab fault extends
northwestward from Moab for more than 30 miles (McKnight, 1940, p. 120,
121, pl. 1).

As shown in figure 23, soon after leaving the checking station the park
road begins to ascend the first of several switchbacks, and cuts first
into the Slick Rock Member, then the Dewey Bridge Member, and finally
the Navajo Sandstone the rest of the way to and beyond the top of the
hill.

From points a mile or so up the hill may be seen interesting features in
several directions.[5] The view to the southwest is shown in figure 23,
to the west are the Three Penguins (fig. 24). A good view of the Moab
Valley is had by looking southeastward (fig. 25). A well in the Navajo
Sandstone at the base of the hill supplies water to all the residences
and to the Visitor Center, where a drinking fountain and modern
restrooms are available to the public. Storage is provided by a steel
tank hidden in a ravine above the buildings shown in figure 25.

To the north the wall of Entrada Sandstone is cut by a normal fault
(fig. 6), as shown in figure 26.

    [Illustration: FAULTED SEVEN MILE-MOAB VALLEY ANTICLINE. Top, View
    toward the southwest from park road about 1 mile above entrance
    station. Bottom, Geologic interpretation of photograph in part after
    McKnight (1940, pl. 1). Moab fault and branch fault (both normal
    faults, fig. 6) unite just beyond ridge of Slick Rock Member. Total
    vertical displacement along both faults is about 2,500 feet. H.F.,
    unnamed upper member of Hermosa Formation; M.F., Moenkopi Formation;
    D, downthrown side of faults; U, upthrown side. Valley fill and
    slope wash of recent (Holocene) age obscure faults and underlying
    rocks. The original sequence of the rocks may be visualized by
    placing the Navajo Sandstone, the upper part of which is exposed at
    the lower right, on top of the Kayenta Formation, the lower few feet
    of which cap and protect the cliffs of Wingate Sandstone in the
    background. The Pacific Northwest (gas) Pipeline mentioned on page
    15 is buried beneath the slice of the Moenkopi Formation between the
    two faults, which accounts for the disturbed appearance of the rock.
    (Fig. 23)]

    [Illustration: Geologic interpretation of photograph]

    [Illustration: THREE PENGUINS, viewed westward from park road about
    1 mile above entrance station. Penguins are carved in massive Slick
    Rock Member seen resting upon thin-bedded Dewey Bridge Member. (Fig.
    24)]

    [Illustration: MOAB VALLEY, viewed southeastward from park road
    about 1 mile above entrance station. Moab fault in about middle of
    valley, hidden beneath recent (Holocene) valley fill and slope wash,
    separates unnamed upper member of Hermosa Formation just above U.S.
    Highway 163 on right from Navajo Sandstone forming hills on left and
    ledges in foreground. Park Service residences at base of hill. White
    patch bordering Colorado River on northwest is tailings pile of
    Atlas Corporation's uranium mill. Moab and Spanish Valley are beyond
    river, and south end of La Sal Mountains forms distant skyline.
    (Fig. 25)]

    [Illustration: FAULTED WALL OF ENTRADA SANDSTONE, north of park road
    about 1 mile above entrance station. Fault is nearly vertical and
    normal (fig. 6), but fault trace slopes steeply downward to right,
    separating upthrown Slick Rock and Dewey Bridge Members on left from
    downthrown Slick Rock Member on right. Light-colored rock in
    foreground is Navajo Sandstone. Displacement probably does not
    exceed 50 feet. (Fig. 26)]

    [Illustration: PARK AVENUE, viewed to the north along trail. (Fig.
    27)]


                         Courthouse Towers Area

About 2.3 miles from the entrance station is a turnoff and parking area
at the south end of the Park Avenue trail (stop 2), which is about 1
mile long and ends at another parking area 1.7 miles farther north. An
interesting hike is best made from south to north in a downhill
direction, and hikers generally meet the cars of relatives or friends
awaiting them at the northern parking area. The trail begins in a canyon
cut in the soft Dewey Bridge Member and walled by high fins of the Slick
Rock Member (fig. 27), but farther north the canyon is floored by the
bare Navajo Sandstone. The avenue was named from the resemblance of the
east wall to a row of tall buildings. Atop the west wall, just to the
left of the view in figure 27, are two balanced rocks (fig. 28). The one
on the left, which resembles somewhat the head of an Egyptian queen, is
offset to the right along a bedding plane, and this offset may have been
caused by an earthquake.

As we progress toward Courthouse Towers proper, lofty fins and monoliths
lie mostly on our left, and to the right are fine distant views of the
La Sal Mountains (stop 4). A general view of the Courthouse Towers is
shown in figure 29, and closeups of two of the named rock
sculptures--the Three Gossips and Sheep Rock--are shown in figures 30
and 31. Just beyond Sheep Rock, which some think resembles the Sphinx,
we see "Baby Arch," shown in figure 15.

Five miles from the entrance station, the road crosses Courthouse Wash
on a modern bridge (stop 6)--a distinct improvement over the two tracks
in the sand we used in 1946. The Courthouse syncline, named after the
wash, extends northwestward through here. (See figs. 8, 9, 20.) About a
mile west of the bridge, Professor Stevens found another pothole arch. A
mile and a half north of the bridge is stop 7, where attention is called
in the booklet to the vast area of "petrified dunes" east of the road,
which are simply dunelike exposures of the crossbedded Navajo Sandstone
formed originally by the cementation of a vast area of sand dunes. My
view of these was taken about 1 mile beyond the stop (fig. 32).

    [Illustration: BALANCED ROCKS ON SOUTH WALL OF PARK AVENUE, at south
    end of trail. (Fig. 28)]

    [Illustration: COURTHOUSE TOWERS, viewed to the northwest from point
    on park road about three-fourths of a mile northeast of the south
    end of Park Avenue trail. Sandstone towers are Slick Rock Member
    resting on Dewey Bridge Member, which also forms foreground. Three
    Gossips at upper left, Sheep Rock just beyond. The Organ and Tower
    of Babel are on right. (Fig. 29)]

    [Illustration: THE THREE GOSSIPS, shown at upper left of figure 29.
    (Fig. 30)]

    [Illustration: SHEEP ROCK, shown on center-left skyline in figure
    29. (Fig. 31)]

West of the road between the petrified dunes and The Windows section,
the Entrada Sandstone, particularly the Dewey Bridge Member, has been
weathered into grotesque spires and pinnacles resembling the so-called
"hoodoos and goblins" in Goblin Valley State Park, just north of
Hanksville, Utah. Typical examples of "hoodoos and goblins" are shown in
figure 33 (near stop 8). It seems reasonable to assume that some of
these spires are the skeletal remains of former arch abutments. From
here may be seen North and South Windows and Turret Arch on the skyline
to the northeast (figs. 37-40).

    [Illustration: PETRIFIED SAND DUNES, looking northeast from park
    road 2.7 miles north of Courthouse Wash. The Navajo Sandstone was
    once a huge sandpile of dunes laid down by winds during an arid
    interval, so it is interesting to note that the irregularly
    weathered sandstone once again resembles a pile of crossbedded
    dunes. See also figure 35. (Fig. 32)]

    [Illustration: "HOODOOS AND GOBLINS," weathered from Dewey Bridge
    Member, viewed northwest from park road about 2-1/2 miles north of
    Courthouse Wash. (Fig. 33)]


                          The Windows Section

The Windows section, one of the most beautiful parts of the park, once
was the only readily accessible part of the former monument and is still
the only collection of arches seen by many visitors who either do not
have or do not take time to travel farther north. All the arches and
erosion forms are on or near a high crest called Elephant Butte (Dane,
1935, p. 126, 127), which separates Salt Valley from the Courthouse
syncline. The ridge also marks the south edge of several minor
anticlines and synclines termed by Dane the "Elephant Butte folds."

    [Illustration: EYE OF THE WHALE, one of several arches in Herdina
    Park, just south of jeep trail about 2 miles northwest of Balanced
    Rock. Cut in Slick Rock Member. Front opening is 60 feet wide and 27
    feet high, but back opening is only 35 feet wide and 11 feet high.
    Photograph by Professor Dale J. Stevens, Brigham Young University.
    (Fig. 34)]

Guarding the approach to The Windows section is Balanced Rock (stop 9).
As shown in the frontispiece, it is accompanied on the right by another
balanced rock and a third one may be seen in the distance. The original
route to The Windows section, pioneered by Goulding, passed just north
of Balanced Rock. Traces of the old road between here and the Garden of
Eden parking area are still visible but no longer used. To the west,
however, a part of the old road is the starting point of a jeep trail
leading northwestward through Herdina Park to a point near Klondike
Bluffs, where it joins the dirt road in Salt Valley (fig. 1). Visitors
having four-wheel-drive vehicles may wish to drive at least as far as
Eye of The Whale (fig. 34), which is about 2 miles northwest of Balanced
Rock. There are several picnic tables at the beginning of this jeep
trail, but no water.

    [Illustration: INTRICATE CROSSBEDS IN NAVAJO SANDSTONE, on north
    side of road between Garden of Eden and Cove of Caves. Red crest is
    basal part of Dewey Bridge Member. (Fig. 35)]

Just beyond Balanced Rock, a branch paved road turns eastward 2-1/2
miles to the main parking lots in The Windows section. Between the
Garden of Eden (stop 13) and Cove of Caves are spectacular exposures of
the Navajo Sandstone showing the crossbedding typical of the original
dunes (fig. 35). Just east of the crossbedded Navajo Sandstone, shown in
figure 35, we pass Cove Arch and Cove of Caves (stop 10) on the north
side of the road (fig. 36).

Just around the curve east of Cove of Caves is the first of two parking
lots (stop 11) forming a one-way loop at the end of this branch of the
road. From the loop may be seen the greatest concentration of readily
accessible arches in the park, all of which are roofed by the Slick Rock
Member and floored by the Dewey Bridge Member. Let us take the short
paved trail from the upper lot to the southeast, where we come first to
North Window (fig. 37). If we walk through this arch and climb the rock
beyond (fig. 37 caption), we see one of the best views in the park (fig.
38). A short walk south of North Window brings us to South Window (fig.
39). The other side of this arch may be reached either by walking around
the nearby southeast end of the fin or by walking through North Window.
A short walk to the southwest brings us to Turret Arch--the one seen
through North Window in figure 38. Figure 40 was taken from the
southwest side of Turret Arch, viewed northeastward toward South Window,
one corner of which appears at the left. Both North and South Windows
may be seen in one photograph taken from points near Turret Arch.

    [Illustration: COVE ARCH AND COVE OF CAVES, on north side of road
    just west of Double Arch and Parade of Elephants. Arch at left and
    three of the caves on right are roofed by Slick Rock Member and
    floored by Dewey Bridge Member. Arch is 48-1/2 feet wide and 34 feet
    high. In time the caves will eat through the 30-foot-thick fin and
    become arches. Note sharp contact between Dewey Bridge Member and
    Navajo Sandstone. (Fig. 36)]

    [Illustration: NORTH WINDOW, viewed to the northeast. Large rock
    seemingly partly blocking left end of arch actually is the southeast
    end of a fin some 50 feet or more beyond the arch, from which figure
    38 was taken. Arch is 93 feet wide and 51 feet high. (Fig. 37)]

From the lower parking lot (stop 12), a short walk by paved trail takes
us to spectacular Double Arch, shown in figure 17. This arch is visible
from the parking lot but is best seen and photographed from at or near
the end of the trail. Looking westward from near the trail's end, we see
the Parade of Elephants, shown in figure 41. This feature is described
on pages 16 and 17 of "The Guide to an Auto Tour of Arches National
Park" as "whimsical stone statuary resembling a circus pachyderm parade.
With tail in trunk, the elephants rumble toward you along a sandstone
roadway."

Ribbon Arch, on the north side of Elephant Butte, is one of the most
delicate ones in the park (fig. 1). Although it is 50 feet wide and 55
feet high, the rock span is only 1-1/2 feet wide and 1 foot thick.

On the way back to the intersection with the main park road, we pass
stop 14, from which may be seen Pothole Arch (fig. 18). One and one-half
miles north of the intersection with the main road is the Panorama Point
parking area (stop 15), which affords fine distant views of Salt and
Cache Valleys and points beyond. A roadside exhibit portrays the gradual
development of the Salt Valley anticline, which supplements my
description on pages 27-32. A parking space a short distance farther
down the hill (stop 16) provides good distant views of the Fiery
Furnace. I tried several telephoto shots from this viewpoint, but
preferred my closeup views, such as the one shown in figure 44.

    [Illustration: LOOKING SOUTHWESTWARD THROUGH NORTH WINDOW, from fin
    shown beyond left side of North Window in figure 37. Turret Arch
    (fig. 40) is seen at right middle ground, south rim of Moab Valley
    to left of arch, Colorado River canyon forms left skyline. (Fig.
    38)]

    [Illustration: SOUTH WINDOW, viewed toward northeast. Arch is 105
    feet wide and 66 feet high. See text. (Fig. 39)]


                           Delicate Arch Area

Two and a half miles northeast of the road intersection near Balanced
Rock, a gravelled side road leads northeastward to several points of
considerable interest. The photograph in figure 11 was taken from this
side road about half a mile northeast of the intersection. About 2 miles
to the northeast, just beyond Salt Valley Wash, is a parking area (stop
17) at the beginning of the trail past Wolfe's Bar-DX Ranch (fig. 3) to
famed Delicate Arch, which is featured on the front cover. Although the
trail to the arch is only 1-1/2 miles long, it crosses several hills at
the outset, then climbs 500 feet, mostly on bare Entrada Sandstone, so
is considered quite strenuous, particularly in hot weather. The Park
Service advises hikers to carry water. The Walt Disney crew, cameras,
gear, cougars, and all climbed this trail in the hottest part of the
summer of 1971 (see p. 16), while my wife and I were working in the
vicinity. Visitors who do not wish to make the hike may get a distant
view of Delicate Arch by driving to a parking area (stop 18) 1.3 miles
farther east.

    [Illustration: TURRET ARCH, viewed northeast toward South Window,
    part of which is visible on left. Small opening on right is visible
    also in figure 38. Largest arch is 39 feet wide and 64 feet high;
    smaller one is 12 feet wide and 13 feet high. A still smaller one,
    not visible in the photograph, is 8 feet wide and only 4-1/2 feet
    high. (Fig. 40)]

    [Illustration: PARADE OF ELEPHANTS, viewed west from end of trail to
    Double Arch. Two elephants are on right, one on left. (Fig. 41)]

After leaving Wolfe's Ranch, the trail to Delicate Arch crosses Salt
Wash on a suspension foot bridge (fig. 42). Just beyond the bridge, a
short walk to the left (north) leads to the Ute petroglyphs shown in the
lower photograph of figure 2. The most difficult part of the trail, on
bare sandstone, is marked by cairns of stones placed at sufficient
intervals to keep hikers from losing the barely visible trail. When the
summit finally is reached and the last corner rounded, one suddenly sees
perhaps the most sublime view in the park--famed Delicate Arch, framing
part of the La Sal Mountains beyond (fig. 43). This graceful arch and
mighty Landscape Arch (fig. 53) were considered to be in serious
jeopardy during the era of sonic booms, but hopefully this danger now is
past. (See p. 16-17.)

It may be of interest to shutterbugs that professional photographer Hal
Rumel lugged an 8- x 10-inch camera plus a heavy tripod and accessories
up the steep trail to get the excellent photograph of Delicate Arch
shown in figure 43. The late afternoon sun intensified the red somewhat,
but my shots made earlier in the day using both 4- x 5-inch and 35-mm
equipment resulted in unwanted shadows, even though the salmon color of
the Slick Rock Member was more nearly normal.

After leaving the junction with the side road, the main park road
traverses slices of vertical strata squeezed between faults along the
north side of Salt Valley, then gradually climbs out of the valley for
about 2 miles to a parking area (stop 19), from which good views are had
of the southeast end of Salt Valley and of the grabens in the west end
of Cache Valley. (See fig. 11.)

    [Illustration: Petroglyph figure]

    [Illustration: SUSPENSION FOOT BRIDGE ACROSS SALT WASH, in front of
    Wolfe's cabin at beginning of Delicate Arch trail. (Fig. 42)]

    [Illustration: DELICATE ARCH, from end of trail 1-1/2 miles above
    Wolfe's Ranch. The opening is 33 feet wide and 45 feet high. The
    left abutment is only 5 feet wide at the narrowest point. The arch
    is carved near the top of the Slick Rock Member, and the top of the
    span, 19 feet thick, is capped by a few feet of the more resistant
    Moab Member, as is Broken Arch (fig. 16). Photograph by Hal Rumel,
    Salt Lake City. (Fig. 43)]


                             Fiery Furnace

About half a mile farther uphill is a parking area for viewing the
southeastern part of the Fiery Furnace (stop 20), a vast array of
towering fins and pinnacles of the reddish Slick Rock Member separated
by narrow slots, vaguely resembling flames shooting skyward. The view of
the Fiery Furnace in figure 44 was taken about 1 mile farther up the
hill. It is not difficult to get lost among this myriad of fins and
narrow slots, so ranger-guided tours are conducted during the summer.

About 1 mile farther northwest is a parking area (stop 23) from which a
short walk to the north end of Fiery Furnace leads to a narrow slot
between high fins (fig. 45), along which a short sandy trail leads to a
recess along the southwest wall containing Sand Dune Arch (fig. 46).
This hidden arch receives sunshine only near the middle of the day and
is a delightful, shady place to rest.

From the entrance to the slot leading to Sand Dune Arch, a trail goes
half a mile north across an open field to Broken Arch, shown in figure
16. This field, which separates the Fiery Furnace and Devils Garden
areas, is seen from the air in figure 12.

    [Illustration: Petroglyph figure]

    [Illustration: FIERY FURNACE, viewed northwest along park road about
    1 mile northwest from stop 20. Fins and spires are of the jointed
    Slick Rock Member (fig. 12), but the top of the Dewey Bridge Member
    is seen to the right of the curve in the road. (Fig. 44)]

    [Illustration: TRAIL TO SAND DUNE ARCH, looking northwest away from
    arch, between towering fins of Slick Rock Member, at northwest end
    of Fiery Furnace. Southeast end of Devils Garden in distance. (Fig.
    45)]

    [Illustration: SAND DUNE ARCH, in recess along southwest wall of
    narrow slot shown in figure 45. Slick Rock Member. (Fig. 46)]


                    Salt Valley and Klondike Bluffs

Before proceeding to the end of the paved road, let us take an
unimproved side road, which turns south about a third of a mile beyond
the last stop, in order to see more of Salt Valley and to visit Klondike
Bluffs in the northwestern part of the park. After descending 2.3 miles
of winding road we reach the normally dry bed of Salt Valley Wash, and
turn abruptly to the northwest. For the next three-fourths of a mile the
"road" is simply two tracks in the loose, sandy bed of the wash, which
obviously should not be travelled when flooded or when there is even a
hint of rain. In dry weather, however, this road may be travelled by
ordinary passenger car. This stretch of the wash cuts through an
intruded block of the Paradox Member of the Hermosa Formation consisting
mainly of gray and brown gypsum, the common salt having been dissolved
out by ground water. Such an intrusive block of salt-bearing rock is
known to geologists as a diapir--not to be confused with the garment
(diaper) worn by infants.

From here on the road traverses a rather uninteresting stretch of valley
north of Salt Valley Wash. Eleven miles from the starting point, the
road reaches an intersection from which a side road leads southwestward
three-fourths of a mile to a parking area at the foot of Klondike
Bluffs, which form the south side of Salt Valley. From here, one may
make a strenuous hike over a primitive trail about 1-1/2 miles long to
beautiful Tower Arch (fig. 47).

The valley road continues northwestward from the intersection to and
beyond the northwest end of the park and connects with roads to Crescent
Junction, Thompson, and the Yellow Cat mining district, north of the
park (p. 14).

Let us return to the paved road and continue our tour of the park.


                             Devils Garden

Turning left (northwest) at the intersection with the paved park road,
we enter Devils Garden--another large maze of towering red fins
separated by narrow slots, which resembles the Fiery Furnace. After a
third of a mile, we reach stop 24 and walk 100 feet or more to the north
for a good view of Skyline Arch (fig. 48). This arch is very
appropriately named, as it forms the skyline viewed either from the road
on the south or from the campground on the north, from points south of
the amphitheater. Less well known is the fact that Skyline Arch is
clearly visible to the naked eye or through binoculars from stretches of
Highway I-70 (or old U.S. Highways 6 and 50) about 11 miles to the
north. Most arches and other erosion forms do not change appearance much
from day to day or year to year, but some, like "Baby Arch" (fig. 15),
show evidence of relatively recent origin. In November 1940 (Abbey,
1971, p. 42) Skyline Arch suddenly doubled in size by the fall of a
large rock that occupied what is now the northwest half of the arch.
Photographs taken before and after this event appear on pages 24 and 25
of the road guide and also in the museum at the Visitor Center.

    [Illustration: TOWER ARCH, on Klondike Bluffs, viewed eastward. Arch
    is in Slick Rock Member but tower on left, after which arch was
    named, is capped by a protective layer of the resistant Moab Member.
    Opening is 88 feet wide and 43 feet high. Photograph by Robert D.
    Miller. (Fig. 47)]

    [Illustration: SKYLINE ARCH, viewed north from point about 100 feet
    north of stop 24, in Slick Rock Member. Although fins are vertical,
    note that the strata seem to dip about 15° to the right, although
    the actual dip is to the northeast. (See fig. 50.) (Fig. 48)]

Another half mile brings us to a one-way (to right) loop at the end of
the park road. Just beyond the beginning of the loop is a parking lot
and very attractive picnic area containing several picnic tables shaded
by piñon pines at the foot of a towering red fin of the Slick Rock
Member. Just north of this picnic ground, a paved side road leads
eastward into a truly beautiful, well-equipped campground comprising
both back-in and drive-through campsites for trailers, campers, or
tents; three pairs of modern restrooms, hydrants, and drinking
fountains; and an amphitheater, where illustrated campfire talks are
given nightly during the summer. The east end of the campground is shown
in figure 49.

    [Illustration: CAMPGROUND IN DEVILS GARDEN, viewed northwestward
    across turn-around at southeastern end. (Fig. 49)]

Devils Garden in general and the campground in particular are on the
crest of a ridge separating Salt Valley to the southwest from the Sagers
Wash syncline to the northeast, which lies north of Yellow Cat Flat and
north of the area shown in figure 1. From the higher parts of the
campground striking views are to be had toward the north and northeast,
particularly late in the afternoon, as shown in figure 50.

    [Illustration: VIEW NORTH FROM CAMPGROUND, in late afternoon.
    Reddish Slick Rock Member capped by light-colored Moab Member are
    seen dipping northeastward toward Sagers Wash syncline. Book Cliffs,
    north of Thompson, are 16 miles north on left skyline. (Fig. 50)]

In about the middle of the one-way loop at the end of the park road is a
well that supplies water to the campground from early in the spring
until the return of freezing weather late in the fall. The well, which
was drilled in 1962 to a depth of 900 feet, obtains a small amount of
water from the Wingate Sandstone. No water was found in the overlying
Navajo and Entrada Sandstones because of the pronounced dip of the rocks
toward the northeast, which allows any water in these rocks to drain
northeastward (Ted Arnow, written commun., 1963). Water from this well
is pumped to a steel tank in a high part of the campground, whence it
flows by gravity to the three sets of restrooms.

    [Illustration: SOUTHEASTERN PART OF DEVILS GARDEN TRAIL, viewed
    northwestward. Narrow slot between fins of Slick Rock Member
    indicates local spacing of joints. (Fig. 51)]

At the northwest end of the one-way loop is a large parking area for use
by people hiking the Devils Garden trail. This trail leads to seven of
the most interesting arches in the park, all of which are in the Slick
Rock Member, and there are many more farther to the northwest. The
approximate distances to the seven arches are given in the paragraphs
that follow. The trail is paved for about 1 mile as far as Landscape
Arch (fig. 53), but from there to Double O Arch (fig. 56) the trail is
primitive, and the Park Service recommends rubber soles as part of the
trail is on bare sandstone. For these reasons, many visitors hike only
as far as Landscape Arch.

    [Illustration: PINE TREE ARCH, viewed northeastward. Opening is 46
    feet wide and 48 feet high. Fin is 30 feet thick. (Fig. 52)]

Much of the trail, particularly the first part, lies in a narrow slot
between fins of the Slick Rock Member, as shown in figure 51. After
about half a mile, a side trail to the north leads to a Y, the
right-hand fork of which goes to Tunnel Arch (fig. 14). The left-hand
fork leads to Pine Tree Arch, obviously named for the piñon pine framed
by this arch (fig. 52).

At the end of the improved part of the trail, we reach Landscape Arch
(fig. 53), claimed by the Park Service to be the longest known natural
arch in the world. According to Ouellette (1958) it is 291 feet long and
118 feet high, but Professor Stevens' measurements indicate it to be 287
feet long and 106 feet high. At its thinnest point on the right, the
span is only 11 feet wide and 11 feet thick. In 1958 three young men
made what was claimed to be the second known ascent of Landscape Arch,
using ropes and other climbing gear, after which they walked across
(Ouellette, 1958). This crossing was made with the permission of a park
ranger, but such permission is no longer given, for the safety of both
the arch and of would-be climbers.

Wall Arch is about a quarter of a mile beyond the end of the improved
part of the trail, and another three-fourths mile brings us to Navajo
Arch (fig. 54) and Partition Arch (fig. 55). A distant view of Partition
Arch may be had just before reaching Landscape Arch. Part of the
remaining trail to Double O Arch (fig. 56) is on the top of a low
sandstone fin, in part between somewhat higher fins and in part above
lower slots.

    [Illustration: LANDSCAPE ARCH, viewed southwestward from near end of
    improved part of Devils Garden trail. Note that ground beneath arch
    is covered by slope wash and near the middle with what appears to be
    a small landslide. Slick Rock Member here is more nearly buff than
    salmon colored, because of a smaller content of iron oxide. Fresh
    breaks and angular blocks of stone at right abutment indicate
    relatively recent rock falls. See text for size. (Fig. 53)]

    [Illustration: NAVAJO ARCH, viewed northeastward from a branch of
    Devils Garden trail. One of few arches having a flat soil-covered
    floor. Opening is 40-1/2 feet wide. Photograph by National Park
    Service. (Fig. 54)]

Beautiful Double O Arch (fig. 56) is at the end of the Devils Garden
trail about 2-1/2 miles northwest of the trailhead. About half a mile
northwest of the trail's end is a prominent landmark called Dark Angel
(fig. 57), which is visible in figure 12 and from the unimproved road in
Salt Valley.

    [Illustration: PARTITION ARCH, viewed southwestward from near Devils
    Garden trail. Arch frames part of south wall of Salt Valley and, on
    skyline, mesas south of Moab Valley. Opening is 27-1/2 feet wide and
    26 feet high. A smaller opening to the right measures 8-1/2 feet
    wide and 8 feet high. Photograph by Dawn E. Reed. (Fig. 55)]

    [Illustration: DOUBLE O ARCH, viewed about north from northwest end
    of Devils Garden trail. Large opening is 71 feet wide and 45 feet
    high; small one at lower left is 21 feet wide and 11 feet high. Span
    of large opening is 11 feet wide and 6 feet thick. Arch frames a
    part of the Book Cliffs about 14 miles to the north. Photograph by
    Hildegard Hamilton, Flagstaff, Ariz. (Fig. 56)]

    [Illustration: DARK ANGEL, a shaft of the Slick Rock Member that is
    an erosional remnant of a once high, narrow fin. About one-half mile
    northwest of Double O Arch. Photograph by National Park Service.
    (Fig. 57)]

    [Illustration: "INDIAN-HEAD ARCH," in upper Devils Garden. Arch and
    most of head are in Slick Rock Member, top of head is basal part of
    Moab Member. Opening is 4 feet wide and 4-1/2 feet high. Photograph
    by Professor Dale J. Stevens, Brigham Young University. (Fig. 58)]

    [Illustration: GEOLOGIC TIME SPIRAL, showing the sequence, names,
    and ages of the geologic eras, periods, and epochs, and the
    evolution of plant and animal life on land and in the sea. The
    primitive animals that evolved in the sea during the vast
    Precambrian Era left few traces in the rocks because they had not
    developed hard parts, such as shells, but hard shell or skeletal
    parts became abundant during and after the Paleozoic Era. (Fig. 59)]




                             GEOLOGIC TIME
                          The Age of the Earth

    The Earth is very old--4.5 billion years or more according to recent
    estimates. Most of the evidence for an ancient Earth is contained in
    the rocks that form the Earth's crust. The rock layers
    themselves--like pages in a long and complicated history--record the
    surface-shaping events of the past, and buried within them are
    traces of life--the plants and animals that evolved from organic
    structures that existed perhaps 3 billion years ago.

    Also contained in rocks once molten are radioactive elements whose
    isotopes provide Earth scientists with an atomic clock. Within these
    rocks, "parent" isotopes decay at a predictable rate to form
    "daughter" isotopes. By determining the relative amounts of parent
    and daughter isotopes, the age of these rocks can be calculated.

    Thus, the results of studies of rock layers (stratigraphy), and of
    fossils (paleontology), coupled with the ages of certain rocks as
    measured by atomic clocks (geochronology), attest to a very old
    Earth!

Professor Stevens found 14 arches in what he called upper Devils Garden,
northwest of Double O Arch, and two arches in the northwesternmost
extension of the park known as Eagle Park (fig. 1). One of the unnamed
arches in upper Devils Garden is shown in figure 58. I am tentatively
calling it "Indian-Head Arch," because of the rather obvious
resemblance.

This ends our journey through Arches National Park, but there remains
for consideration a summary of the principal geologic events leading to
the formation of this beautiful part of the Colorado Plateau and a brief
comparison with the geology of other national parks and monuments on the
Plateau.




                      Summary of Geologic History


Having finished our geologic trip through Arches National Park, let us
see how the arches and other features fit into the bigger scheme of
things--the geologic age and events of the Earth as a whole, as depicted
in figure 59. As shown in figure 4, the rock strata still preserved in
the park range in age from Pennsylvanian to Cretaceous, or from about
300 million to 100 million years old--a span of about 200 million years.
This seems an incredibly long time, until one notes that the earth is
some 4.5 billion years old, and that our rock pile is but 1/23 or 4-1/2
percent of the age of the Earth as a whole. Thus, in figure 59, the
rocks exposed in the park occupy only about the left half of the top
whorl of the spiral.

But this is not the whole story. As indicated earlier, younger Mesozoic
and Tertiary rocks more than 1 mile thick that once covered the area
have been carried away by erosion, and if we include these the span is
increased to about 250 million years, or nearly a full whorl of the
spiral.

Deep tests for oil and gas tell us that much older rocks underlie the
area, and we have seen that some of these played a part in shaping the
park we see today. In addition to the Precambrian igneous and
metamorphic rocks, there is about 2,000 feet of Paleozoic sedimentary
rocks older than the Pennsylvanian Paradox Member of the Hermosa
Formation, most of which was laid down in ancient seas. This includes
strata of Cambrian, Ordovician, Devonian, Mississippian, and
Pennsylvanian ages (fig. 59). There are some gaps in the rock record
caused by temporary emergence of the land above sea level and erosion of
the land surface before the land again subsided below sea level so that
deposition could resume. Silurian rocks are absent, presumably because,
here, the Silurian Period was dominated by erosion rather than
deposition.

While Pennsylvanian and Permian rocks were being laid down in and
southwest of the park, a large area to the northeast, called by
geologists the Uncompahgre Highland (because it occupied the same
general area as part of the present Uncompahgre Plateau), rose slowly
above sea level. Whatever Paleozoic rocks were on this rising land plus
part of the underlying Precambrian rocks were eroded and carried by
streams into deep basins to the northeast and southwest. Thus, while
some marine or near-shore deposits were being laid down in and south of
the park, thousands of feet of red beds were being laid down by streams
between the park and what is now the Uncompahgre Plateau. During part of
Middle Pennsylvanian time, a large area, including the park, known as
the Paradox basin, was alternately connected to or cut off from the sea,
so that the water was evaporated during cutoff periods and replenished
during periods when connection with the sea resumed. In these huge
evaporation basins were deposited the salt and gypsum plus some potash
salts and shale that now make up the Paradox Member of the Hermosa
Formation.

Arches National Park contains four northwesterly trending major
folds--the Salt Valley and Cache Valley salt anticlines, the Courthouse
syncline, and the faulted Moab-Seven Mile anticline, which forms the
southwestern border. How these folds were formed was explained on pages
27-32. The history of their growth, however, was a long one that began
about 300 million years ago in the Pennsylvanian and ended about 50
million years ago in the early Tertiary. The growth of these folds
occurred in two stages. The first stage, which involved the development
of the salt cores of the anticlines, ended in the Jurassic with the
beginning of Morrison time; the second stage, which involved additional
folding that intensified the magnitude and shape of existing folds,
occurred in the early Tertiary and was followed later by collapse of the
salt anticlines. The formation and collapse of the Salt Valley and Cache
Valley anticlines was accompanied by pronounced jointing (fig. 12),
which allowed differential erosion to produce the tall fins in which the
arches were formed.

The old Uncompahgre Highland continued to shed debris into the bordering
basins until Triassic time, when it began to be covered by a veneer of
red sandstone and siltstone of the Chinle Formation (Lohman, 1965). The
area remained above sea level during the Triassic Period and most, if
not all, of the Jurassic Period, although the Jurassic Carmel Formation
was laid down in a sea that lay just to the west.

Late in the Cretaceous Period a large part of Central and Southeastern
United States, including the eastern half of Utah, sank beneath the sea
and received thousands of feet of mud, silt, and some sand that later
compacted into the Mancos Shale. This formation, as well as all younger
and some older strata, has long since been eroded from most of the park
area, but a little of the Mancos is preserved in the Cache Valley graben
(fig. 11), and the entire Mancos Shale and younger rocks are present in
adjacent areas, such as the Book Cliffs north of Green River, Crescent
Junction, and Cisco (figs. 7, 50, 56).

The land rose above the sea at about the close of the Cretaceous and has
remained above ever since, although inland basins and lakes received
sediment during parts of the Tertiary Period. Compressive forces in the
Earth's crust produced some gentle folding of the strata at the close of
the Cretaceous, but more pronounced folding and some faulting occurred
during the Eocene Epoch, when most of the Rocky Mountains took form.
During the Miocene Epoch igneous rock welled up into older rocks to form
the cores of the nearby La Sal, Abajo, and Henry Mountains. Additional
uplift and some folding occurred in the Pliocene and Pleistocene Epochs.

Much of the course of the Colorado River was established during the
Miocene Epoch, with some additional adjustments in the late Pliocene and
early Pleistocene Epochs (Hunt, C. B., 1969, p. 67). Erosion during much
of the Tertiary Period and all of the Quaternary Period plus some
sagging and breaking of the crest of the anticlines, brought on by
solution and lateral squeezing of salt beds beneath the Moab-Seven Mile,
Salt Valley, and Cache Valley anticlines, combined to produce the
landscape as we now see it.

The Precambrian rocks beneath the area are about 1.5 billion years old;
so an enormous span of time is represented by the rocks and events in
and beneath Canyonlands National Park.

If we consider the geologic formations that make up the national parks
(N.P.), national monuments (N.M.) (excluding small historical or
archaeological ones), Monument Valley, San Rafael Swell, and Glen Canyon
National Recreation Area, all in the Colorado Plateau, it becomes
apparent that certain formations or groups of formations play starring
roles in some parks or monuments, some play supporting roles, and in a
few places the entire cast of rocks gets about equal billing. Let us
compare them and see how and where they fit into the "Geologic Time
Spiral" (fig. 59).

Dinosaur N.M., with exposed rocks ranging in age from Precambrian to
Cretaceous, covers the greatest time span (nearly 2 billion years), but
has one unit--the Jurassic Morrison Formation--in the starring role, for
this unit contains the many dinosaur fossils that give the monument its
name and fame, although there are several older units in supporting
roles. Grand Canyon N.P. and N.M. are next, with rocks ranging in age
from Precambrian through Permian (excluding the Quaternary lava flows in
the N.M.), but here there is truly a team effort, for the entire cast
gets about equal billing. Canyonlands N.P. stands third in this
category, with rocks ranging from Pennsylvanian to Jurassic, but we
would have to give top billing to the Permian Cedar Mesa Sandstone
Member of the Cutler Formation, from which The Needles, The Grabens, and
most of the arches were sculptured; the Triassic Wingate Sandstone and
the Triassic(?) Kayenta Formation get second billing for their roles in
forming and preserving Island in the Sky and other high mesas.

Now let us consider other areas with only one or few players in the
cast, beginning at the bottom of the time spiral. Black Canyon of the
Gunnison N.M., cut entirely in rocks of early Precambrian age with only
a veneer of much younger rocks, obviously has but one star in its cast.
Colorado N.M. contains rocks ranging from Precambrian to
Cretaceous--equal to Dinosaur in this respect, but Colorado is unique in
that all the rocks of the long Paleozoic Era and some others are missing
from the cast; of those that remain, the Triassic Wingate and the
Triassic(?) Kayenta are the stars, with strong support from the Jurassic
Entrada Sandstone.

All the bridges in Natural Bridges N.M. were carved from the Permian
Cedar Mesa Sandstone Member of the Cutler Formation, also one of the
stars in Canyonlands N.P. In Canyon de Chelly (pronounced dee shay) N.M.
and Monument Valley (neither a national park nor a national monument, as
it is owned and administered by the Navajo Tribe), the De Chelly
Sandstone Member of the Cutler Formation--a Permian member younger than
the Cedar Mesa--plays the starring role.

Wupatki N.M. near Flagstaff, Ariz., stars the Triassic Moenkopi
Formation. Petrified Forest N.P. (which now includes part of the Painted
Desert) has but one star--the Triassic Chinle Formation, in which are
found many petrified logs and stumps of ancient trees. The
Triassic-Jurassic Glen Canyon Group (fig. 19), which includes the
Triassic Wingate Sandstone, the Triassic(?) Kayenta Formation, and the
Triassic(?)-Jurassic Navajo Sandstone, receives top billing in recently
enlarged Capitol Reef N.P., but the Triassic Moenkopi and Chinle
Formations enjoy supporting roles.

The Triassic(?)-Jurassic Navajo Sandstone, which has a supporting role
in Arches N.P., is the undisputed star of Zion N.P., Rainbow Bridge
N.M., and Glen Canyon National Recreation Area, despite the fact that
the latter is the type locality of the entire Glen Canyon Group. The
Navajo also forms the impressive reef at the east edge of the beautiful
San Rafael Swell, a dome, or closed anticline, now crossed by Highway
I-70 between Green River and Fremont Junction, Utah.

As we journey upward in the time spiral (fig. 59), we come to the
Jurassic Entrada Sandstone, which stars in Arches N.P., with help from
the underlying Navajo Sandstone, and a supporting cast of both older and
younger rocks. The Entrada also forms the grotesque erosion forms called
"hoodoos and goblins" in Goblin Valley State Park, north of Hanksville,
Utah.

Moving ever upward in the spiral, we come to the Cretaceous--the age of
the starring Mesaverde Group, in which the caves of Mesaverde N.P. were
formed, and which now house beautifully preserved ruins once occupied by
the Anasazi, the same ancient people who once dwelt in Arches N.P. and
nearby areas.

This brings us up to the Tertiary Period, during the early part of which
the pink limestones and shales of the Paleocene and Eocene Wasatch
Formation were laid down in inland basins. Beautifully sculptured
cliffs, pinnacles, and caves of the Wasatch star in Bryce Canyon N.P.
and in nearby Cedar Breaks N.M. This concludes our climb up the time
spiral, except for Quaternary volcanoes and some older volcanic features
at Sunset Crater N.M., near Flagstaff, Ariz.

Thus, one way or another, many rock units formed during the last couple
of billion years have performed on the stage of the Colorado Plateau
and, hamlike, still lurk in the wings eagerly awaiting your applause to
recall them to the footlights. Don't let them down--visit and enjoy the
national parks and monuments of the Plateau, for they probably are the
greatest collection of scenic wonderlands in the world.




                           Additional Reading


Many reports covering various aspects of the area have been cited in the
text by author and year, and these plus a few additional ones are listed
in "Selected References." A few works of general or special interest
should be mentioned, however.

Between 1926 and 1929 the entire area now included in the park was
mapped geologically in classic reports by Dane (1935) and by McKnight
(1940). These men and their field assistants mapped the area by use of
the plane-table and telescopic alidade without benefit of modern
topographic maps or aerial photographs, except for topographic maps of
the narrow stretch along the Colorado River mapped under the direction
of Herron (1917). Only small sections could be reached by automobile, so
nearly all the area was traversed using horses and mules or by hiking.
This work plus mapping done in nearby areas to the south and to the
north (Stokes, 1952) during the uranium boom of the mid-fifties was used
by Williams (1964) in compiling a geologic map of the Moab quadrangle at
a scale of 1:250,000.

Several early reports on the Colorado River and its potential
utilization contain a wealth of information and many fine photographs,
including two by La Rue (1916, 1925) and one by Follansbee (1929).

You may be interested in brief accounts of the geology of other national
parks and monuments, or other areas of special interest, such as the
reports on the Uinta Mountains by Hansen (1969), Mount Rainier by
Crandell (1969), Yellowstone National Park by Keefer (1971), and ones by
me on Colorado National Monument (Lohman, 1965) and Canyonlands National
Park (1974).

For those who wish to learn more about the science of geology, I suggest
the textbook by Gilluly, Waters, and Woodford (1968).




                            Acknowledgments


I am greatly indebted to Bates Wilson, former Superintendent, and to
former Assistant Superintendent Joe Carithers, for their splendid
cooperation in supplying data and information; to Chuck Budge, former
Chief Ranger; Dave May, Assistant Chief of Interpretation and Resource
Management; Joe Miller, former Maintenance Engineer; Bob Kerr, new
Superintendent; Maxine Newell, Park Historian and member of the staff at
Arches National Park; Jerry Banta, former Park Ranger at Arches; and
Carl Mikesell, Park Ranger at Arches, for their many favors.

I am grateful to several colleagues and friends for the loan of
photographs, for geologic help and data, and for reviewing this report.
I am also deeply grateful to my wife, Ruth, for accompanying me on all
the fieldwork and for her help and encouragement.




                          Selected References


  Abbey, Edward, 1971, Desert solitaire, a season in the wilderness: New
          York, Ballantine Books, 303 p.
  Baker, A. A., 1933, Geology and oil possibilities of the Moab
          district, Grand and San Juan Counties, Utah: U.S. Geol. Survey
          Bull. 841, 95 p.
  Baker, Pearl, 1971, The Wild Bunch at Robbers Roost: New York,
          Aberlard-Schuman, 224 p.
  Beckwith, Frank, 1934, A group of petroglyphs near Moab, Utah: Santa
          Fe, N. Mex., El Palacio, v. 36, p. 177-178.
  Breed, Jack, 1947, Utah's arches of stone: Natl. Geog. Mag., p.
          173-192, August.
  Case, J. E., and Joesting, H. R., 1972, Regional geophysical
          investigations in the central Colorado Plateau: U.S. Geol.
          Survey Prof. Paper 736, 34 p.
  Cater, F. W., 1970, Geology of the salt anticline region in
          southwestern Colorado: U.S. Geol. Survey Prof. Paper 637, 80
          p.
  ---- 1972, Salt anticlines within the Paradox Basin, _in_ Geologic
          atlas of the Rocky Mountain region, United States of America:
          Denver, Colo., Rocky Mtn. Assoc. of Geologists, p. 137, 138,
          fig. 4.
  Cleland, H. F., 1910, North American natural bridges, with a
          discussion of their origins: Geol. Soc. America Bull., v. 21,
          p. 313-338.
  Crandell, D. R., 1969, The geologic story of Mt. Rainier: U.S. Geol.
          Survey Bull. 1292, 43 p.
  Dane, C. H., 1935, Geology of the Salt Valley anticline and adjacent
          areas, Grand County, Utah: U.S. Geol. Survey Bull. 863, 184 p.
  Dellenbaugh, F. S., 1902, The romance of the Colorado River: New York,
          G. P. Putnam's Sons, 399 p. [reprinted 1962 by Rio Grande
          Press, Chicago, Ill.]
  Everhart, W. C., 1972, The National Park Service, Praeger Library of
          U.S. Government Departments and Agencies No. 13: New York,
          Praeger Publishers, p. i-xii, 1-276.
  Follansbee, Robert, 1929, Upper Colorado River and its utilization:
          U.S. Geol. Survey Water-Supply Paper 617, 394 p.
  Gilluly, James, Waters, A. C., and Woodford, A. O., 1968, Principles
          of geology [3d ed.]: San Francisco, W. R. Freeman & Co., 685
          p.
  Hansen, W. R., 1969, The geologic story of the Uinta Mountains [with
          graphics by John R. Stacy]: U.S. Geol. Survey Bull. 1291, 144
          p.
  Herron, W. R., 1917, Profile surveys in the Colorado River Basin in
          Wyoming, Utah, Colorado, and New Mexico: U.S. Geol. Survey
          Water-Supply Paper 396, 6 p., 43 pls.
  Hite, R. J., 1972, Pennsylvanian rocks, _in_ Geologic atlas of the
          Rocky Mountain region, United States of America: Denver,
          Colo., Rocky Mtn. Assoc. of Geologists, p. 133-137.
  Hite, R. J., and Lohman, S. W., 1973, Geologic appraisal of Paradox
          basin salt deposits for waste emplacement: U.S. Geol. Survey
          open-file report, 75 p.
  Hunt, Alice, 1956, Archeology of southeastern Utah, _in_ Geology and
          economic deposits of east-central Utah: Salt Lake City,
          Intermountain Assoc. of Petroleum Geologists, 7th Ann. Field
          Conf., p. 13-18.
  Hunt, C. B., 1956, Cenozoic geology of the Colorado Plateau: U.S.
          Geol. Survey Prof. Paper 279, 99 p.
  ---- 1969, Geologic history of the Colorado River, _in_ The Colorado
          River region and John Wesley Powell: U.S. Geol. Survey Prof.
          Paper 669, p. I-IV, 59-130.
  Jennings, J. D., 1970, Canyonlands-Aborigines: Naturalist, v. 21,
          Summer, Special Issue no. 2, p. 10-15.
  Joesting, H. R., Case, J. E., and Plouff, Donald, 1966, Regional
          geophysical investigations of the Moab-Needles area, Utah:
          U.S. Geol. Survey Prof. Paper 516-C, 21 p.
  Keefer, W. R., 1971, The geologic story of Yellowstone National Park,
          illustrated by John R. Stacy: U.S. Geol. Survey Bull. 1347, 92
          p. [1972].
  Lansford, Henry, 1972, Boatman in the desert, a passenger-carrying
          sternwheeler in canyon country: "Empire" [magazine of the
          Denver Post], Nov. 5, p. 18, 19.
  La Rue, E. C., 1916, Colorado River and its utilization: U.S. Geol.
          Survey Water-Supply Paper 395, 231 p.
  ---- 1925, Water power and flood control of Colorado River below Green
          River, Utah, with a foreword by Hubert Work, Secretary of the
          Interior, p. 1-100. [Appendix A, A report on water supply, by
          E. C. La Rue and G. F. Holbrook, p. 101-123; and Appendix B, A
          geologic report on the inner gorge of the Grand Canyon of
          Colorado River, by R. C. Moore, p. 125-171]: U.S. Geol. Survey
          Water-Supply Paper 556, 176 p.
  Lohman, S. W., 1965, The geologic story of Colorado National Monument
          [with graphics by John R. Stacy]: Fruita, Colo., Colorado and
          Black Canyon Natural History Assoc., 56 p.
  ---- 1974, The geologic story of Canyonlands National Park, with
          graphics by John R. Stacy: U.S. Geol. Survey Bull. 1327, 126
          p.
  McKnight, E. T., 1940, Geology of area between Green and Colorado
          Rivers, Grand and San Juan Counties, Utah: U.S. Geol. Survey
          Bull. 908, 147 p.
  Ouellette, C. M., 1958, Over the top of Landscape Arch: Desert Mag.,
          p. 13-16, March.
  Pierson, Lloyd, 1960, Arches National Monument, _in_ Geology of the
          Paradox basin fold and fault belt: Durango, Colo., Four
          Corners Geol. Soc. Guidebook, 3d Ann. Field Conf., p. 17-21.
  Schaafsma, Polly, 1971, Rock art of Utah: Cambridge, Mass., Harvard
          Univ., Papers of the Peabody Museum of Archaeology and
          Ethnology, v. 65, 169 p.
  Stacy, J. R., 1962, Shortcut method for the preparation of
          shaded-relief illustrations, _in_ Short papers in geology,
          hydrology, and topography 1962: U.S. Geol. Survey Prof. Paper
          450-D, p. D164-D165.
  Stokes, W. L., 1952, Uranium-vanadium deposits of the Thompsons area,
          Grand County, Utah, with emphasis on the origin of carnotite
          ores: Utah Geol. and Mineralogical Survey Bull. 46, 51 p.,
          December.
  ---- 1970, Canyonlands--Geology: Naturalist, v. 21, Summer, Special
          Issue no. 2, p. 3-9.
  Walters, H. H., 1956, Pacific Northwest Pipeline--The scenic inch,
          _in_ Geology and economic deposits of east-central Utah: Salt
          Lake City, Intermountain Assoc. of Petroleum Geologists, p.
          169-170.
  Williams, P. L., 1964, Geology, structure, and uranium deposits of the
          Moab quadrangle, Colorado and Utah: U.S. Geol. Survey Misc.
          Geol. Inv. Map I-360.
  Wilson, B. E., 1956, Arches National Monument, _in_ Geology and
          economic deposits of east-central Utah: Salt Lake City,
          Intermountain Assoc. of Petroleum Geologists, 7th Ann. Field
          Conf., p. 50-51.
  Wright, J. C., Shawe, D. R., and Lohman, S. W., 1962, Definition of
          members of the Jurassic Entrada Sandstone in east-central Utah
          and west-central Colorado: Bull. Am. Assoc. Petroleum
          Geologists, v. 46, no. 11, p. 2057-2070.


    [Illustration: Petroglyph figure]




Footnotes


[1]Mrs. Tanner, of Phoenix, Ariz., is the author of an earlier history
    of Moab (her hometown). She has completed a revision entitled, "The
    Far Country--A Regional History of Moab and La Sal, Utah," which
    will be serialized in the Moab Times-Independent, after which it
    will be published.

[2]For the benefit of visitors from countries in which the metric system
    is used, the following conversion factors may be helpful: 1 inch =
    2.54 centimeters, 1 foot = 0.305 meter, 1 mile = 1.609 kilometers, 1
    U.S. gallon = 0.00379 cubic meter.

[3]Barrier Creek flows through Horseshoe Canyon in the detached unit of
    Canyonlands National Park. The canyon walls are adorned by striking
    pictographs (Lohman, 1974, fig. 2). "Barrier Canyon style" is named
    after the pictographs found in Horseshoe Canyon.

[4]Plastic-relief maps are no longer available from the U.S. Army Map
    Service but may be obtained from the T. N. Hubbard Scientific Co.,
    Box 105, Northbrook, Ill. 60062. A topographic map at a scale of
    1:250,000 of the Moab quadrangle and similar maps at a scale of
    1:62,500 for the Thompson, Cisco, Moab, and Castle Valley
    quadrangles are available from the U.S. Geological Survey, Denver
    Distribution Section, Federal Center, Denver, Colo. 80225, from the
    Canyonlands Natural History Association at Moab, and from privately
    owned shops where maps are sold. Most of the park is covered by the
    Thompson and Moab quadrangles. The southern part of the park is
    shown also on the Moab 4 NW, Moab 4 NE, and Mt. Waas 3 NW
    quadrangles at a scale of 1:24,000. A special topographic map of
    Arches National Park at a scale of 1:50,000 is in preparation by the
    U.S. Geological Survey. These maps also may be obtained from the
    above-listed sources.

[5]This is numbered stop 1 in the booklet referred to earlier "The Guide
    to an Auto Tour of Arches National Park," and corresponds to the
    numeral one on a small sign at the roadside parking place. Some of
    the other numbers are given in the pages that follow.




                                 Index


            [Italic page numbers indicate major references]


                                   A
                                                                     Page
  Abajo Mountains                                                     101
      artifacts                                                         9
  Abbey, Edward                                                         3
  Aborigines, occupation of area                                        9
  Acknowledgments                                                   _105_
  Anasazi people, petroglyphs                                          10
  Anasazi ruins                                                    9, 103
  Ancestral Colorado River                                             33
  Anomalies, gravity, Salt Valley                                      32
  Anticlines, salt                                                     31
  Arches, broken remains                                               44
      examples                                                       _46_
      former abutments                                                 68
      horizontal                                                       44
      how they are formed                                              42
      natural, defined                                               _40_
      number in the park                                         40, _41_
      origin and development                                           37
      pothole                                                          44
      vertical                                                     42, 44
  Artifacts, La Sal and Abajo Mountains                                 9
  Aspinall, Wayne, Representative                                       8


                                    B
  "Baby Arch"                                                  46, 63, 83
  Balanced Rock                                                69, 70, 74
  Banta, Jerry                                                        105
  Bar-DX Ranch                                                 12, 13, 14
  "Barrier Canyon style"                                               10
  Bedding, wavy, Dewey Bridge Member                                   46
  Beeson, Stib                                                         13
  Beginning of a monument                                             _1_
  Bending of rocks                                                   _24_
  Bennett, Wallace F., Senator                                          8
  Beroni, Pete                                                     14, 15
  Black Canyon of the Gunnison National Monument                      102
  Book Cliffs                                                         100
  Breaking of rocks                                                  _24_
  Bridge, natural, defined                                           _40_
  Broken Arch                                                      46, 79
  Brown-Stanton expedition, exploration                                15
  Bryce Canyon National Park                                          103
  Budge, Chuck                                                        105


                                    C
  Cache Valley                                                 56, 73, 77
  Cache Valley anticline                         25, 32, 34, 55, 100, 101
  Cache Valley graben                                             34, 100
  Campground                                                           86
      water supply                                                     87
  Cane Creek anticline                                                 24
  Canyon de Chelly National Monument                                  102
  _Canyon King_                                                         8
  Canyon Lands Section, Colorado Plateau                            9, 22
  Canyonlands National Park                                 3, 9, 15, 102
  Canyonlands Natural History Association                               8
  Capitol Reef National Park                                          103
  Carithers, Joe                                                      105
  Carmel Formation                                                    100
  Cassidy, Butch                                                       12
  Caves, Entrada Sandstone                                              9
  Cedar Breaks National Monument                                      103
  Cedar Mesa Sandstone Member, Cutler Formation                   22, 102
  Chinle Formation                                      32, 100, 102, 103
  "Cisco Cutoff"                                                       16
  Civilian Conservation Corps                                           2
  Cliff dwellers                                                        9
  Climate, desert                                                  35, 51
      wetter, different landscape produced                             37
  Collapse, salt anticlines                                        33, 34
  Color photographs, equipment used                                     8
  Colorado National Monument                                          102
  Colorado Plateau, geologic formations included                      101
      rock formations                                            103, 104
      subdivisions                                                     18
      uranium-vanadium mining                                          14
  Colorado Plateaus Province                                           18
  Colorado River, course established                                  101
      nighttime illuminated float trip                             16, 52
  Colorado River canyon                                      35, 51, _52_
  Cores, salt                                                         100
  Corral mine                                                          15
  Courthouse syncline                     25, 30, 31, 32, 52, 63, 68, 100
  Courthouse Towers area                                         25, _63_
      number of arches                                                 41
  Courthouse Wash                                        2, 3, 18, 35, 63
  Cove Arch                                                            70
  Cove of Caves                                                        70
  Crossbedding, Navajo Sandstone                               63, 66, 70
  Cutler Formation                                                32, 102
      Cedar Mesa Sandstone Member                                      22
      White Rim Sandstone Member                                       22


                                    D
  Dark Angel                                                           92
  De Chelly Sandstone Member, Cutler Formation                        102
  Dead Horse Point                                                     33
  Dedication of the park                                                8
  Delicate Arch                                        16, 25, 74, 75, 77
  Delicate Arch area, number of arches                                 41
  Density, average, Paradox Member                                     32
  Deposition of rock materials, environments                         _20_
  Desert varnish                                                       10
  Development of the arches                                          _37_
  Devils Garden                                    2, 5, 25, 79, _83_, 86
      fins                                                             42
      number of arches                                                 41
      trail                                                        88, 92
  Dewey Bridge                                                         52
  Dewey Bridge Member                                              46, 63
      Entrada Sandstone, composition                                   41
          "hoodoos and goblins"                                        66
          park road cutting                                            57
          The Windows section                                          71
          vertical arches                                              44
  "Dewey Road"                                                         16
  Diapir                                                               83
  Differential erosion                                                 42
  Dinosaur National Monument                                     101, 102
  Dissimilarity of Arches vs. Canyonlands                          23, 24
  Double Arch                                                   2, 46, 72
  Double O Arch                                                90, 92, 98
  Drainage, Arches National Park                                       18
  Dry Mesa                                                          5, 56


                                    E
  Eagle Park                                                       25, 98
      number of arches                                                 41
  Early dwellers                                                      _9_
  Earthquake, rock offset along bedding plane                          63
  Egyptian queen, arch resembling                                      63
  Eisenhower, Dwight D., Mission 66                                     4
  Elephant Butte                                                       72
  Elephant Butte folds                                                 68
  Elizondo, Emmett                                                     13
  Entrada Sandstone                                      23, 74, 102, 103
      arches, modes of origin                                          42
      caves                                                             9
      cut by normal fault                                              57
      Moab Member                                                      24
      no water found                                                   87
  Environments of deposition                                         _20_
  Erosion                                                              99
      Colorado Plateau                                               _33_
  Evaporation basins                                                   99
  Evaporites                                                           30
  Eye of The Whale                                                     69


                                    F
  Facies changes                                                       22
  "Father of the monument," J. W. Williams                           1, 4
  Faults, Cache Valley anticline                                       34
      Salt Valley anticline                                            34
  Fiery Furnace                                      25, 42, 73, _79_, 83
      number of arches                                                 41
  Fins                                                             63, 79
  Float trip, nighttime illuminated, down Colorado River               52
  Folds                                                     _24_, 30, 100
  Four-wheel-drive vehicles                                            69
  Fractures                                                          _24_
  Fremont people, occupation of area                                    9
      pictographs                                                      10
  Frost, prying action                                                 42


                                    G
  Garden of Eden                                               50, 69, 70
  Gas exploration, deep tests                                      15, 99
  Geographic setting                                                 _18_
  Geologic age of rocks in park                                      _98_
  Geologic events forming the Colorado Plateau                       _98_
  Geologic history, summary                                          _98_
  Geologic Time Spiral                                           101, 103
  Geology, at the park entrance                                        57
  Glen Canyon Group                                          52, 102, 103
  Glen Canyon National Recreation Area                           101, 103
  Goblin Valley State Park                                        66, 103
  Gould, Lawrence M.                                                    1
  Goulding, Harry, first person to drive into The Windows section   2, 69
  Grabens                                                              34
  Grand Canyon National Park and National Monument                    102
  Gravity anomalies, Salt Valley                                       32
  Green River                                                         103
  Ground water                                                         41
  "Guide to an Auto Tour of Arches National Park," (The)    5, 50, 51, 72
  Gulf of California                                                   33


                                    H
  Hastier, (Mrs.) Hazel Wolfe                                          13
  Headquarters area                                                  _57_
  Henry Mountains                                                     101
  Herdina Park                                                     25, 69
      number of arches                                                 41
  Hermosa Formation, Paradox Member                    23, 25, 29, 30, 32
  History, early                                                      _9_
      geologic, summary                                              _98_
  "Hoodoos and goblins"                                           66, 103
  Hoover, Herbert, proclamation                                         1
  Horizontal arches                                                    44
  Horseshoe Canyon, pictographs                                        10
  Horseshoe Canyon Detached Unit of Canyonlands                        23
  Humid regions, subdued rounded landforms                             37


                                    I
  Igneous rocks                                                    22, 99
  "Indian-Head Arch"                                                   98
  Iron in the rocks                                                    23
  Island in the Sky                                                   102


                                    J
  Jeep trail                                                       69, 70
  Johnson, Lyndon B., proclamation                                      2
  Joints                                                    _24_, 34, 100


                                    K
  Kayenta Formation                                      35, 52, 102, 103
  Kerr, Bob                                                           105
  Klondike Bluffs                                        25, 69, _82_, 83
      number of arches                                                 41


                                    L
  La Sal Mountains                                        22, 63, 77, 101
      artifacts                                                         9
  Lake Mead                                                            33
  Lake Powell                                                          33
  Land forms, formation in the park                                    33
  Landscape Arch                                               16, 77, 88
      second known ascent                                              90
  Larson, Tommy                                                        13
  Lloyd, Sherman P., Representative                                     8
  Lohman, (Mrs.) Ruth                                                 105


                                    M
  Mahan, Russel L.                                                      2
  Mancos Shale                                                    32, 100
  Maxwell, Ross A., investigation of caves                          9, 10
  May, David                                                      40, 105
  Melich, Mitchell, Solicitor General                                   8
  Mesaverde Group                                                 32, 103
  Mesaverde National Park                                             103
  Metamorphic rocks                                                22, 99
  Metric unit conversion factors                                      _2_
  Mikesell, Carl                                                      105
  Miller, Joe                                                         105
  Mission 66, presidential and congressional support                    4
  Mississippi River sternwheeler replica                                8
  Moab, uranium-vanadium mill                                          14
  Moab bridge                                                          52
  Moab Canyon                                                      15, 18
  Moab fault                                                       26, 57
  Moab Lions Club                                                    1, 8
  "Moab Mail Road"                                                     16
  Moab Member, Entrada Sandstone                                   24, 35
      Entrada Sandstone, Broken Arch                                   46
      composition                                                      41
  "Moab panel"                                                         10
  Moab-Spanish Valley anticline                                        26
  Moab Valley                                                          57
  Moab Valley-Seven Mile anticline                               100, 101
  Moenkopi Formation                                         32, 102, 103
  Monoliths                                                            63
  Monument, beginning                                                 _1_
  Monument Valley                                                101, 102
  Morrison Formation                                              32, 101
  Morton, Rogers C. B., Secretary of the Interior                       8
  Moss, Frank E., Senator                                               8
  Moss Back Member, Chinle Formation                                   15


                                    N
  National Park Service                                 8, 12, 40, 75, 90
  Natural Bridges National Monument                        3, 37, 40, 102
  Navajo Arch                                                          90
  Navajo Sandstone                                        24, 35, 52, 103
      canyon floor                                                     63
      crossbedding                                             63, 66, 70
      park road cutting                                                57
      water supply                                                 57, 87
  Navajo Tribe                                                        102
  Needles section, The, Canyonlands National Park                 16, 102
  Newell, (Mrs.) Maxine                                           12, 105
  Nixon, Richard M., Congressional Bill                                 5
  North Window                                                 40, 68, 71


                                    O
  Oil exploration                                                      15
      Cane Creek anticline                                             24
      deep tests                                                       99
  Origin of the arches                                               _37_


                                    P
  Pacific Northwest Pipeline                                           15
  Painted Desert                                                      102
  Panorama Point                                                       73
  Parade of Elephants                                                  72
  Paradox basin                                                        23
  Paradox Member, Hermosa Formation                23, 25, 29, 30, 82, 99
      Hermosa Formation, average density                               32
          upward intrusion                                             34
  Park, a trip through                                               _52_
      dedication                                                        8
      how to see                                                     _50_
      improvements                                                      4
  Park Avenue, trail                                                   63
  Park Service. _See_ National Park Service.
  Partition Arch                                                       90
  Petrified dunes                                                  63, 66
  Petrified Forest National Park                                      102
  Petroglyphs, Ute                                                 10, 75
  Pictographs, Fremont people                                          10
  Pine Tree Arch                                                       90
  Piñon pines                                                          86
  Pipeline scars, Pacific Northwest Pipeline                           15
  Plateau, uplift and erosion                                        _33_
  Potash occurrence                                                    15
  Pothole Arch                                                     50, 73
  Pothole arches                                                       44
  Powell, John Wesley, Canyonlands National Park                       15
  Professor Valley                                                     56


                                    R
  Rainbow Bridge National Monument                                    103
  Rainwater                                                        41, 42
  Rampton, Calvin L., Utah Governor                                     8
  Reading, additional                                               _104_
  References, selected                                              _105_
  Relief map, shaded, Arches National Park, described              18, 19
  Ribbon Arch                                                          72
  Richardson Amphitheater                                              56
  Richardson, Professor                                                56
  Rico Formation                                                       23
  Rison, (Mrs.) Esther Stanley                                         13
  Rock formations, sculptured by erosion                               35
  Rock openings, natural, types                                        37
  Rock types in the park                                               35
  Roosevelt, Franklin D., proclamation                                  2
  Rumel, Hal, photographer                                             77
  "Run, Cougar, Run"                                           16, 56, 75


                                    S
  Sagers Wash syncline                                                 86
  Salt, occurrence                                                     15
      properties critical to formation of salt anticlines              30
  Salt anticlines                                             30, 31, 100
      collapse                                                     33, 34
  Salt-bearing rock                                                    83
  Salt rolls                                                           31
  Salt Valley                                 2, 68, 73, 77, _82_, 83, 92
      gravity anomalies                                                32
  Salt Valley anticline                      25, 30, 31, 32, 73, 100, 101
      collapse                                                         34
      fins                                                             42
  Salt Valley Wash                                          3, 74, 82, 83
  Salt Wash                                                        35, 55
      Anasazi ruins                                                     9
      drainage                                                         18
      grabens                                                          34
      sandstone caves near                                             10
  Salt Wash Sandstone Member, Morrison Formation                       14
  San Juan Basin, natural gas                                          15
  San Rafael Swell                                               101, 103
  Sand Dune Arch                                                       79
  Sandstone fins                                                   41, 42
  Schaafsma, Polly, quoted                                         10, 12
  Scenic drive, Moab to Cisco                                          16
  "Scenic Inch," Pacific Northwest Pipeline                            15
  Sedimentary rocks                                                    20
      modes of deposition                                              99
  Seven Mile-Moab Valley anticline                             26, 32, 57
  Sevenmile Canyon                                                     15
  Sheep Rock                                                           63
  Skyline Arch                                                         83
  Slick Rock Member, Entrada Sandstone                                 34
      Entrada Sandstone, composition                                   41
          high fins and pinnacles                              63, 79, 86
          hiking trail between fins                                    90
          park road cutting                                            57
          salmon                                                       77
          The Windows section                                          71
          Tunnel Arch                                                  46
          vertical arches                                          42, 44
  Slumping of sediments, irregular                                     50
  Snow                                                             41, 51
  Sonic booms, dangers posed to arches                             16, 17
  South Window                                                 40, 68, 71
  Spanish explorers                                                    12
      introduction of horses to this country                           10
  Squaw Flat Campground                                                16
  Stanley, Esther                                                      13
      (Mrs.) Flora                                                     13
      Volna                                                            13
  Stevens, Dale J.                                     40, 41, 63, 90, 98
  Strata, lateral changes across the park                              22
  Sundance Kid                                                         12
  Sunset Crater National Monument                                     103
  Supersonic flights banned, Moab-Times Independent                    17
  Suspension bridge, Colorado River                                    16


                                    T
  Tanner, (Mrs.) Faun McConkie                                          1
  Taylor, L. L. (Bish)                                                  1
  Temperatures                                                         51
  "The Guide to an Auto Tour of Arches National Park"       5, 50, 51, 72
  The Needles section, Canyonlands National Park                  16, 102
  The Windows section                    25, 41, 46, 51, 66, _68_, 69, 70
  Three Gossips                                                        63
  Three Penguins                                                       57
  Tower Arch                                                           83
  Tunnel Arch                                                  40, 46, 90
  Turnbow, Mary                                                         1
  Turnbow cabin                                                        13
  Turret Arch                                                      68, 71


                                    U
  Uncompahgre Highland                                        23, 99, 100
  Uncompahgre Plateau                                              23, 99
  Uplift, Colorado Plateau                                           _33_
  Upper Devils Garden                                                  98
      number of arches                                                 41
  Uranium mines                                                        14
  Ute petroglyphs                                                  10, 75


                                    V
  Vanadium mines                                                       14
  Vegetation                                                           37
  Vertical arches                                                  42, 44
  Visitor Center                                           50, 51, 57, 86
  Volz, J. Leonard                                                      8


                                    W
  Walker, Lester                                                       13
  Wall Arch                                                            90
  Walt Disney crew, "Run, Cougar, Run"                                 75
  Wasatch Formation                                                    32
  Water supply, Navajo Sandstone                                       57
      to the campground                                                87
  White Rim Sandstone Member, Cutler Formation                         22
  Wild Bunch, The                                                      12
  Williams, J. W.                                                    1, 4
  Wilson, Bates                                                 1, 3, 105
  Wilson, (Mrs.) Bates                                                  3
  Windows, distinguished from arches                                 _40_
  Windows section, The                       25, 46, 51, 66, _68_, 69, 70
      number of arches                                                 41
  Wingate Sandstone                                      35, 87, 102, 103
  Wirth, Conrad L.                                                      4
  Wolfe cabin                                            1, 3, 12, 13, 14
  Wolfe, Fred                                                      12, 13
  Wolfe, John Wesley                                               12, 13
  Wolfe's Bar-DX Ranch                                  9, 10, 14, 74, 75
  Wupatki National Monument                                           102


                                    Y
  Yellow Cat area (Thompson's area)                                    14
  Yellow Cat Flat                                                      86
  Yellow Cat mining district                                           83


                                    Z
  Zion National Park                                                  103

                         *U.S. GOVERNMENT PRINTING OFFICE: 1975--679-138

    [Illustration: U. S. Department of the Interior, March 3, 1849]




Transcriber's Notes


--Retained publication information from the printed edition: this eBook
  is public-domain in the country of publication.

--Corrected a few palpable typos.

--Included a transcription of the text within some images.

--In the text versions only, text in italics is delimited by
  _underscores_.

--The HTML version contains relative hyperlinks to a companion volume on
  Canyonlands National Park, Gutenberg eBook #51048.

--A third book in the series, on Colorado National Monument, was revised
  after this book was printed.