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    [Illustration: Cover: Looking southward along Groton Pond from near
    Stillwater Brook.]




                             THE GEOLOGY OF
                          GROTON STATE FOREST


                                  _By_
                          ROBERT A. CHRISTMAN


                    DEPARTMENT OF FORESTS AND PARKS
                      Perry H. Merrill, _Director_

                     VERMONT DEVELOPMENT COMMISSION

                       VERMONT GEOLOGICAL SURVEY
                   Charles G. Doll, _State Geologist_


                                  1956




                     GEOLOGY OF GROTON STATE FOREST


                                  _By_
                          ROBERT A. CHRISTMAN




                              INTRODUCTION


Geology is the study of the history of the earth as recorded in its
rocks. This study explains why certain types of rocks and minerals occur
at one place and not another, why the forms of the land differ from one
region to another, and why particular animal and plant remains are
sometimes preserved as fossils in certain kinds of rocks. The
professional geologist makes these studies his business; the amateur
finds these studies a fascinating hobby; but the uninitiated person
misses much of the pleasure of travel. Anyone who notices the difference
between rocks or terrains and wonders "why?", has a potential for
geology. Many fall into this class and it is for them that this booklet
has been written. It is hoped that with its aid, the traveler or
vacationer may come to know something about the geology of Groton State
Forest. The author is confident that those who come into the habit of
observing nature and the world around them will find more meaning in
life itself. In any case, those traveling with children may find answers
to some of their questions about minerals, rocks and mountains.

Groton State Forest is not a geologist's paradise--as compared to
Yellowstone Park or the Grand Canyon--but it does contain interesting
rocks and land forms which can be explained geologically. In keeping
with the calm, subdued and mature atmosphere of the Vermont countryside,
the geology is unobtrusive. There are few jutting cliffs or bare rock
exposures; all is mantled with vegetation. If this vegetation could be
stripped away--admittedly, a postulation that would destroy the
wilderness and charm that belongs to Groton--boulders and gravelly
glacial deposits would be seen to fill the valleys. If in turn these
boulders and the soil could be stripped away, a continuous floor of rock
would be exposed. This would be a geologist's paradise--square miles of
bare rock would be available for study. However, lacking the magic wand
to perform this feat, we must be satisfied to glean what information we
can from the existing rock exposures.

To use a pun, it can be said that almost all the rocks found at Groton
State Forest can be taken for granite. As well as has been determined,
all the underlying rock is _granite_[1] and most of the boulders
deposited by glaciers of the last ice age are the same type of granite.
To avoid confusion in describing these rocks, the discussion has been
divided into two parts: the first deals with the granite of the bedrock,
and the second deals with the glaciation of the area and the deposits
resulting from it. A third section describes the geology in some of the
nearby areas.




                       GRANITE AND RELATED ROCKS


_Occurrence of the granite_

Ledges of light-colored granite occur at the summits of most of the
mountains and hills in the State Forest area and are found occasionally
at lower elevations. They are conspicuous on Owlshead, Silver Ledge,
Little Deer, Big Deer, Niggerhead and Spicer Mountains; smaller ledges
also occur on Kettle, and Little Spruce mountains, Hardwood Ridge and
the low hills east of Groton Pond. At lower elevations, granite is found
at the outlet of Groton Pond, along the railroad tracks west of Groton
Pond and at Stillwater Brook, along Osmore brook and at several other
minor locations. These locations are shown diagrammatically on the map
by a black dot. These dots indicate where the granite occurs but nothing
about the extent of the exposure. If every location of exposed rock were
marked with a dot, certain parts of the map, for instance, the west side
of Niggerhead, would be solid black and the contour lines which show the
elevation would be obscured completely.

All these rocks are presumably part of one large mass of granite which
extends deep below the surface of the earth. Most of this body of
granite is hidden by the soil and bouldery glacial deposits, so that its
exact areal extent is not known. It appears likely that it extends to
the southwest to the vicinity of East Barre.


_Description of the granite_

The granite found at Groton State Forest is a gray to white,
medium-grained rock with the mineral grains all about the same size.
Surfaces exposed to weathering are generally darker in color and
frequently are covered with scales of dark colored lichen. If the rock
is broken to reveal an unaltered surface close examination will disclose
individual mineral grains of mica, feldspar and quartz. _Mica_ occurs as
very small plates which appear either white or colorless, called
_muscovite_, or as black shiny plates called _biotite_. The _feldspar_,
which is the most abundant mineral in the granite, has a chalky white
appearance and may occur as tabular grains which reflect light from
their flat surfaces when held in the proper position. _Quartz_, which
contains only silicon and oxygen, the two most common elements in the
earth's crust, is a transparent, glassy mineral which has no flat
surfaces. It may appear gray because one can look down into the glassy
mineral where there is no light source.

A specimen of granite from Owlshead was studied with a microscope after
it had been cut and ground to a thickness of only 0.03 millimeters. Many
minerals, which ordinarily appear to be opaque, are transparent when
ground this thin. By their various optical properties, the different
minerals can be identified and the composition of the rock can be
determined. Figure 1 shows a photograph, taken through a microscope, of
one of these thin sections of granite. By careful examination of the
thin section and by measuring the areal extent of the different minerals
present, the rock was determined to contain, by volume, 35 percent
quartz, 60 percent feldspar (in proportions of 25 percent _microcline_
feldspar, KAlSi_3O_8 and 35 percent _plagioclase_ feldspar, NaAlSi_3O_8)
and 5 percent mica (in proportions of 4 percent biotite and 1 percent
muscovite). Although it is a member of the granite family, this rock
should, in strict terminology, be called a quartz monzonite rather than
a granite to indicate more precisely the mineral composition. Because of
slight differences in composition, granite from the same body may
elsewhere be correctly called granodiorite, quartz diorite or granite
proper, depending on the relative amounts of the two feldspars and
quartz. In this report these close distinctions have not been made and
the rock is simply called granite.


_Cracks in the granite_

Two kinds of natural breaks, or cracks, occur in the granite in the
State Forest area. _Joints_ are breaks which occur along plane surfaces
and _exfoliation_ is the name given to the breakage along curved
surfaces related to the exposure of the rock. Granite, as contrasted
with other rocks, is characterized by its uniformity of texture and
massiveness, so that any cracks present are conspicuous.

    [Illustration: Figure 1. Photomicrograph of a thin section of
    granite from Owlshead Mountain. The mineral with the grid pattern
    (upper left) is a feldspar named microcline which has the
    composition of KAlSi_3O_8. The one with the indistinct striped
    pattern (lower center) is a feldspar named plagioclase, variety
    oligoclase, which has the composition of approximately NaAlSi_3O_8.
    The patterns for these minerals result from different portions of
    the same mineral grain having different orientations, called
    twinning, so as to give a different optical appearance. The clear
    white mineral (right center) is quartz. The dark gray mineral with
    the fine lines (upper center) is biotite and the smaller,
    lighter-colored, elongate mineral to the right of the biotite is
    muscovite. The other minerals are feldspar and quartz in different
    orientations. The actual diameter of the clear white quartz grain
    (right center) is about four-tenths of a millimeter so that the
    photograph is a magnification of about one hundred.]

Joints are more conspicuous of the two types, and typically belong to a
general system so that at a given location they tend to be parallel. On
top of Owlshead, for example, the most prominent joints trend N.25°W.
(read: North twenty-five degrees to the west) with dips[2] that are
vertical or dipping steeply to the southwest. Another set of joints
trends N.10°E. with dips that are vertical or dipping steeply to the
southwest. Joints represent the breakage of the rock due to stress and
strain. Some joints result from tensional forces set up within the rock
itself by contraction due to cooling of the originally hot solidified
rock. Other joints result from larger-scale forces within the earth's
crust which cause earthquakes and general movement of land masses. An
exhaustive study of all the rocks in a large area would be required to
determine conclusively the origin of the joints on Owlshead.

In addition to the nearly vertical joints, a third set of nearly
horizontal joints may be observed on cliffs. These joints are called
_sheeting_ and apparently are related to the depth from a former
topographic surface which existed at the time the sheeting originated.
The vertical joints and sheeting are important qualities of a rock to be
considered in choosing a rock for commercial quarrying. Not only do
these factors effect the ease of quarrying, but they also determine the
amount of waste material which would have to be removed and discarded
because of poor size and shape.

Exfoliation is the term for breakage due to the disintegration caused by
decomposition of the rock on surfaces exposed to the weather. It is
characterized by the scaling off of concentric shells of altered rock to
produce a convex surface. Rocks showing exfoliation surfaces are not
common at Groton. One of the best developed exfoliation surfaces,
illustrated in Figure 2, occurs at the base of the cliffs on the south
side of Owlshead Mountain.

Once joints have formed, they are enlarged by weathering. In particular,
rocks are pushed apart by a "frost wedging." When water freezes it
expands by about one-tenth of its volume. If it is confined it may exert
a pressure of as much as 138 tons per square foot. In this manner, huge
blocks may be pushed apart. If they are at the edge of a cliff, or part
of the cliff itself, they may eventually break off and fall to the slope
below. The accumulation of broken rock at the base of a cliff is called
_talus_.


_Origin and age of the granite_

The granite originated in the interior of the earth many million years
ago as a molten mass, called _magma_. This magma moved upward through
the earth's crust by a process of melting the pre-existing rock or by
forcefully pushing it aside. When it reached its present position it
became cooler and minerals began to crystallize out. However, as is
shown in Figure 3, it is important to understand that the surface of the
land was not in its present position and that the magma actually cooled
beneath a considerable thickness of other rocks. These overlying rocks,
now gone, acted as an insulator and prevented the magma from cooling too
quickly. If the magma had risen through these rocks and reached their
upper surface, it would have formed a lava flow similar to those of
present-day volcanoes and would have cooled much more rapidly. Rocks
formed near the surface are characterized either by being fine-grained
without visible crystals or by having a few large crystals in a
fine-grained matrix; they never have a uniformly,
medium-to-coarse-grained texture. Thus, the texture of the granite at
Groton State Forest proves that it cooled slowly and indicates that, at
the time of cooling, the granite was not at the surface. This is a
reasonable postulation because studies of the regional geology indicate
that a large amount of rock has been removed from this area by erosion
through the long periods of geologic time.

    [Illustration: Figure 2. Exfoliation surface on the south side of
    Owlshead Mountain. Joints, of the sheeting type, are visible in the
    granite cliff. The decomposition of the granite by weathering in the
    niches has resulted in small patches of soil. The boy in the upper
    right gives the scale.]

    [Illustration: Figure 3. Sequence of events at Groton State Forest
    shown diagrammatically.]

    [Illustration: A. The Waits River Formation and other younger
    formations are deposited from a shallow sea during Ordovician time.]

  YOUNGER FORMATIONS
  WAITS RIVER FORMATION

    [Illustration: B. The sedimentary rocks are folded and metamorphosed
    and the granite is intruded into the older rocks and crystallizes
    during Devonian time.]

  WAITS RIVER FORMATION
  GRANITE

    [Illustration: C. Erosion removes much of the rock from the area.]

  GRANITE

    [Illustration: D. During the ice age, continental glaciers move over
    the land and erosion by the ice forms Owlshead Mountain and the
    basin for Groton Pond.]

  ICE
  GRANITE

    [Illustration: E. Present topography, exaggerated.]

  OWLSHEAD MOUNTAIN
  RICKER MILLS

Evidence that the granite was emplaced into the older rocks of the
earth's crust can be seen at certain locations outside of the State
Forest. At Ricker Mills, for example, narrow bodies of granite can be
seen cross cutting the older rocks. A fuller description of the geology
at Ricker Mills is given in a later section of this report. Another type
of evidence showing that the granite came into older rocks is found in
the occurrence of fragments of older rock incorporated into the granite.
These are called _inclusions_ and represent broken pieces of older rock
which were enveloped by the granite. Inclusions are like peach slices in
jello in that the surrounding material solidified after they were
dropped in. Inclusions were observed in rocks on top of Kettle and Jerry
Lund Mountains.

Near the covered picnic shelter at Ricker Pond, one of the large granite
boulders deposited by the glacier contains inclusions. Although this
boulder has been moved from its original occurrence, it probably has not
moved far as it is composed of the white granite which is typical of the
area. It is cut by several pegmatitic dikes. The most interesting
feature is the occurrence of inclusions of elongate, layered bands of
older rocks of gray to dark gray _schist_.[3] These relations are shown
in the sketch of this boulder in Figure 4. A careful examination of the
schist inclusions reveals that they contain small plates of biotite in a
fine matrix of quartz and more mica. The contact between the schist and
granite is gradational at places because when the rock was formed the
hot molten granite was in the process of melting the solid schist. The
schist resembles the rock which occurred in this area before the granite
was intruded and which occurs in nearby areas where no granite is
exposed. Older rocks of somewhat similar appearance can be seen at
Ricker Mills and on top of Jerry Lund Mountain.

The composition of the granite at Groton State Forest is nearly the same
as that which occurs throughout this region of Vermont. Incomplete
mapping suggests that the granite at Groton is part of a large mass
which extends to the southwest to the vicinity of East Barre.
Undoubtedly all the granitic rocks of this region are related although
they are not continuous at the surface. They were all emplaced at about
the same time following a mountain-building episode in which the older
rocks were folded and metamorphosed. On the geologic time scale, the
granites were emplaced near the end of the Devonian period which is
estimated to be more than 300 million years ago.

    [Illustration: Figure 4. Sketch of boulder of granite containing
    pegmatite band and schist inclusions at picnic area at Ricker Pond.]

  GRANITE
  PEGMATITE
  SCHIST


_Aplite and pegmatite_

Two other types of igneous rocks called aplite and pegmatite occur
sparingly in Groton State Forest. Both of these are productions of
crystallization of residual fluids or late stage magma related to the
granite. These were emplaced along cracks or planes of weakness in the
granite after the granite had solidified. When viewed from the surface
the aplite or pegmatite generally appear as bands cutting through the
granite. However, when the third-dimension is considered it is easily
realized that they are tabular or sheet-like in shape. Igneous rock
masses having these dimensions are called _dikes_. At Groton most of the
dikes are nearly vertical with a thickness ranging from less than an
inch to more than several feet and extending for considerable distances.
On Owlshead, one of these dikes is nearly three feet thick. The extent
of these dikes is not known because they are only partly exposed, in
that they extend beyond the limited areas of rock exposure.

    [Illustration:            GROTON STATE FOREST]

    DREW MTN
    NIGGERHEAD MTN
    BLAKE HILL
    NIGGERHEAD BROOK
    KETTLE MTN
    SPICER MTN
    OWLSHEAD MTN
    KETTLE POND
    STILLWATER BK.
    HARDWOOD RIDGE
    BEAVER BROOK
    SILVER LEDGE
    LITTLE SPRUCE MTN
    PEACHAM POND
    DEER MTN
    DEVIL'S HILL
    PEACHAM BOG
    LITTLE DEER MTN
    OSMORE BK.
    COLDWATER BK.
    GROTON POND
    JERRY LUND MTN
    RICKER POND
    RICKER MILLS
  EXPLANATION
    GRANITE EXPOSURES
    SCHIST EXPOSURES
    TRAIL
    RAILROAD
    SWAMPY AREAS
    CONTOUR LINE WITH ELEVATION
    CONTOUR INTERVAL IS 100 FEET
      TOPOGRAPHY FROM U. S. GEOLOGICAL SURVEY MAPS
      BY ROBERT CHRISTMAN

The _pegmatite_ dikes are coarse-grained, in some cases consisting of
individual mineral grains as much as two to four inches in diameter. The
mineral composition of the pegmatites is nearly the same as the granite,
except that biotite is usually absent. Because of their larger grain
size, the minerals can be recognized more easily in pegmatites than in
either granite or aplite. Quartz is glassy and breaks with smooth curved
fractures. Feldspar is chalky white, or pink, and may occur as tabular
crystals with straight-line contacts. It tends to break along definite
intersecting planes which can be seen in their reflecting position.
Muscovite occurs as "books" of semi-transparent leaves. The large
"books" of muscovite are particularly interesting because of the
fascinating fact that a mineral sheet can be split along a given planar
direction into thinner and thinner sheets until they are too thin to
handle. Theoretically the mineral might be split into sheets only as
thick as one layer of atoms. The ability of a mineral to break along
definite planes is related to its atomic structure and is called
_cleavage_. The cleavage in mica is perfect, whereas the cleavage in
feldspar is only poorly developed, and quartz does not possess cleavage
at all.

The _aplite_ dikes are composed of nearly the same minerals as granite
except that the average grain size is smaller. They are characterized by
the absence of dark minerals and muscovite and by a high quartz content
which gives the rock a "sugary" appearance. Most of the aplite dikes are
less than six inches thick.

Inasmuch as the pegmatite and aplite dikes both cut through the granite,
they both must be younger in age than the granite. As is shown by the
relations between these two types on Owlshead (reproduced in Figure 5),
the pegmatite dike is younger because it cuts across the aplite dike.
This is the general age relationship for these dikes in this age.

    [Illustration: Figure 5. Sketch showing aplite and pegmatite dikes
    in the granite on Owlshead Mountain. The cross cutting relations
    show that the pegmatite is youngest and that aplite is younger than
    the granite but older than the pegmatite. In the distance is Kettle
    Pond and Kettle Mountain.]

  GRANITE
  APLITE
  PEGMATITE




                               GLACIATION


Although the causes of the ice ages remain a matter for conjecture, the
fact is established that the northern part of North America was covered
by a thick sheet of moving ice several different times beginning about a
million years ago. As the effect of the last glaciation erased much of
the evidence of previous glaciations, the present topography can be
related to that last one. Rather accurate dating by measuring the
radioactive decay of Carbon 14, indicates that the ice of the last
glaciation retreated from the area about 12,000 years ago. Because the
climates between the four glaciations were as warm, if not warmer, than
our present-day climate, geologists have speculated that the world may
now be in a warm period and that another ice age is scheduled to occur
some time in the distant future.

The effect of continental glaciation upon a land mass is twofold. First,
the glaciation acts as an erosive agent which tends to scoop out the
areas of softer rock and wear down the areas of more resistant rock.
Secondly, when the glacier begins to melt, it drops large quantities of
gravel and boulders which had become incorporated within the glacier.
Most of this material is picked up by the glacier as it moves over the
land; some falls onto the glacier where it occupies a valley. Some of
the sand, gravel and boulder deposits left by the glacier are
distinctive in form and composition and others are characterized by
their complete lack of distinctive shapes, and the utterly chaotic
nature of the material deposited. The deposits at Groton State Forest
seem to be the latter type.


_Erosion and deposition by the glacier_

The shape of Spicer, Owlshead, Little Deer and Big Deer mountains are
primarily the result of the erosive action of the glacier as it
continually moved southward over the land for a great number of years
during the last glaciation. When a continental glacier encounters a hill
or mountain of resistant rock, it tends to scour the rock on the up-ice
side of the hill and to "pluck out" the rocks on the leeward side. For
this reason these mountains have broad gentle slopes on the side from
which the glacier came and they drop off sharply on the side from which
material was removed by plucking action. The last part of Figure 3
illustrates how these mountains may have been formed. Such prominent
rock exposures which have been subjected to glacial erosion originally
showed deep scratches, called _glacial striae_, cut by cobbles dragged
along the bottom of the glacier. Unfortunately, on most prominences in
Groton State Forest exfoliation of the rock has erased these markings;
but it is possible that striae may be found on recently uncovered rock
exposures.

The depressions in which Groton and Osmore ponds are located probably
represent areas in which the glacier scooped out material to a greater
depth than elsewhere either because of channeling of bottom flow between
topographically prominent features, or because of subtle differences in
rock hardness.

When the glacier retreated, that is when it was melting faster than it
was advancing, it dropped material in a helter-skelter manner. _End
moraines_, which are ridges of gravel formed where the front of the
glacier was stationary because of a close balance between rates of
movement and melting, are not evident in Groton State Forest. As far as
can be determined, the material was deposited irregularly over the
entire area, so that boulders dropped by the glacier are found
everywhere. These are particularly noticeable around the lakes where the
fine material has been removed and the soil and forest cover does not
hide the boulders.

Almost all of the boulders deposited by the glacier are composed of
white granite similar to the rock which underlies the entire area. This
indicates that most of the boulders have not been transported very far.
However, occasionally boulders are found which are not characteristic of
the area and represent rocks brought in from the north. Such boulders
which are foreign to the area in which they are found are called
_erratics_. Most erratics in this area are dark-colored metamorphosed
rocks in which the minerals are oriented to give the rock a layered
pattern. These are called either _gneisses_ or _schists_ depending on
whether the layering is coarse or fine. Deposits of the glacier are
exposed in two gravel or sand pits near the Stillwater Camp site. These
deposits are composed principally of sand but contain scattered boulders
of different sizes. A few erratics are found in these
deposits--particularly a variety of rock which weathers to a soft, brown
porous mass resembling decayed wood. These sandy deposits probably were
plastered onto the ground from the sole of the creeping glacier or were
simply let down as the glacier wasted away.

Because of the irregular manner in which the glacier may deposit its
load of sand and gravel, the topography in such areas is uneven and
characterized by poor drainage. At a number of places in Groton swampy
areas occur at higher elevation which might normally be expected to be
well-drained. Some of these areas have become the sites of beaver dams
because they are ideal for damming up the water.




                        GEOLOGY OF NEARBY AREAS


_Ricker Mills_

Just south of the park at Ricker Mills some of the oldest rocks in the
area are exposed in the railroad cut just north of the highway crossing.
These rocks belong to a thick sequence of similar rocks which are
collectively called the _Waits River formation_. Studies in other areas
indicate that these rocks belong to the portion of geologic time called
the Ordovician period which was more than 350 million years ago.

The Waits River formation represents a series of sediments which
accumulated at the bottom of a shallow sea during Ordovician time. These
sediments included both limy and sandy beds, and fossils may originally
have been preserved in some of the beds. Sediments of other types later
accumulated over the Waits River formation during a long period of
geologic time, so that eventually the formation became deeply buried.
(See Figure 3.) The sea retreated and the rocks were subjected to high
pressure and temperatures during a period of mountain-building. The
rocks which had been sedimentary were folded and converted to
_metamorphic rocks_ by partial melting and recrystallization of the
components. As a result the rocks became schists or marbles. Any fossils
which may have been present were destroyed or badly altered in the
process. This is unfortunate because valuable geologic information as
the age of the rocks can be determined from the type of fossils present.

The rocks of the Waits River formation at Ricker Mills are dominantly
mica schists with layers containing limy material. These are too impure
to be considered marble but enough lime is present so that they react
strongly with acid, a test for detecting the presence of lime. The
schists principally contain quartz, biotite, calcite (lime) with lesser
amounts of muscovite, feldspar and impurities. The rocks weather to dark
colors; the gray limy beds are particularly susceptible to weathering
and turn dark brown to black on the surface. When more lime is present,
the rock weathers to a deep brown porous rock which resembles decayed
wood. Some boulders of these altered limestones are found in the glacial
deposits in the State Forest.

An additional factor which makes the rocks in the railroad cut at Ricker
Mills look "messy" is the iron and manganese staining and the formation
of mineral crusts on the surface of the rocks through the action of
ground water. Rain water falling on the hills above passes through the
soils, dissolving minerals, and precipitating them where the water seeps
out and evaporates at the lower level of the railroad tracks.

The schists trend about N.80°W. and dip about 30° to the northeast.
Along the length of the rock exposures it can be seen that this dip is
not constant but varies from 10 to 30°. The variation in dip gives the
schists a wavy appearance.

At two places along the railroad cut, the schist has been intruded by
granite. As is shown in Figure 6, which is a sketch of the rocks exposed
on the east side of the railroad, the granite forms vertical dikes. As
the schist ends abruptly at the contact of the granite, this indicates
that the granite formed after the schist. The granite is nearly the same
as the granite in Groton State Forest except that the mica is muscovite
rather than biotite. For this reason the granite is lighter in color on
fresh surfaces. In general the exterior is dark in color due to the
staining of iron from weathering of the mineral pyrite, an iron sulfide,
which occurs in small amounts in the granite.


_Jerry Lund Mountain_

On top of Jerry Lund Mountain occur other outcrops of the Waits River
formation and granite. Their exact relationships cannot be seen easily
because of the thick vegetation. The Waits River formation on Jerry Lund
Mountain is composed principally of quartz mica schist.




                             TRIPS TO TAKE


_Hiking in the State Forest_

The hike from the end of the road to the top of Owlshead Mountain takes
only ten to fifteen minutes. A splendid view of the surrounding area,
particularly Groton and Kettle ponds, is obtained from here. If
possible, everyone who visits the park should take this short walk. The
granite is well-exposed at the summit and dikes of aplite and pegmatite
may be seen.

The more venturesome park visitor will want to make other trips away
from the "beaten path" into the wilderness of the Vermont woods. The
principal difficulty arises in that the wilderness is so real a person
may well become lost if he strays too far from the trails. Some of the
trails have become overgrown so that they are difficult to follow and
portions of others have been destroyed by the damming up of brooks by
the beavers. It is suggested that in planning hikes information be
obtained from the park superintendent about the condition of the various
trails.

    [Illustration: Figure 6. Diagrammatic sketch showing the relations
    between the schist of the Waits River formation and the granite on
    the east side of the railroad cut, at Ricker Mills.]

  GRANITE
  WAITS RIVER FORMATION

An interesting hike can be made from Osmore Pond to Deer Mountain but as
the trail is poorly marked, one must maintain a sense of direction. From
the Osmore picnic area walk south near the shore of the pond to its
outlet into Osmore Brook. At this point turn left to the northeast and
follow the trail which parallels a wire marking the edge of the game
preserve. About three-fourths of a mile from Osmore Brook the trail
meets another trail at right angles. To the left the trail follows the
game preserve boundary northwestward. The trail to the right leads
directly to the top of Deer Mountain where a view may be obtained on the
south side of the summit. As an alternate route for returning, follow
the trail along the game preserve to the northwest. Some distance beyond
a shelter-lean-to the trail divides several times with the main trail
leading to Blake Hill and other trails to the left leading to the Osmore
Pond road.

A hike along the trail on the north side of Kettle Pond to the
shelter-lean-tos makes a pleasant trip along the water. Also, the trail
from Owlshead Mountain to Osmore Pond is convenient for a short hike
through the woods, if the trail can be found.


_Quarries at East Barre_

The granite quarries at East Barre are in nearly the same type of rock
as that which occurs at Groton State Forest. The quarry operations are
interesting and educational and the quarries afford a good opportunity
of seeing fresh, unaltered specimens of granite. Guide service is
offered at some of the quarries.




                               FOOTNOTES


[1]_Granite_ is a type of igneous rock consisting of large interlocking
    grains of light-colored minerals. Rocks are classified as being
    either igneous, sedimentary, or metamorphic. _Igneous_ rocks form by
    the solidification of molten material; _sedimentary_ rocks form by
    the accumulation of sediments derived from older rocks; and
    _metamorphic_ rocks form by the recrystallization of older rocks
    under conditions of high temperatures and pressures.

[2]_Dip_ is the inclination of a surface as, for example, a joint
    surface described above.

[3]_Schist_ is the name given to rocks in which the minerals have a
    parallel alignment due to reorganization of the rock constituents
    during a condition of high temperature and pressure. The platy
    minerals, like mica, form at right angles to the pressure so that
    the resulting rock may have a "bedded" appearance.


    [Illustration: Looking northwest over Groton Pond toward Owlshead
    Mountain]

    [Illustration: Looking north over Groton Pond toward Little Deer
    Mountain]




                          Transcriber's Notes


--Silently corrected a few typos.

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

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