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The Geologic Story
of
Glacier National Park
{Cover} CHIEF MOUNTAIN
Special Bulletin No. 3
GLACIER NATURAL HISTORY ASSOCIATION
Price 25 Cents
THE GEOLOGIC STORY
of
GLACIER NATIONAL PARK
By JAMES L. DYSON
Head, Department of Geology and Geography
Lafayette College[1]
Until recently a geologist was visualized by most people as a queer sort
of fellow who went around the countryside breaking rocks with a little
hammer. Fortunately, the general public today has a much clearer picture
of the geologist and his science, but there are still many among us who
mistakenly feel that geology is something too remote for practical
application.
Geology is the science of the Earth. It includes a history of our planet
starting with its origin, and a history of the life which has lived upon
it. From it we can determine the reason for every feature of the
landscape and every rock structure underneath the surface, and we can
further learn what processes gave rise to them.
Practically everything to be seen on the face of the Earth owes its
origin directly or indirectly to geological processes. These may be
grouped into two great categories: Internal forces or agents which
raise, lower, bend, and break the Earth's crust; and external, more
familiar agents such as water, wind, and ice, which wear away the
surface and carry the materials to another place--ultimately to the sea.
Let us consider a few of the products of these geologic agents: (1) The
soil covering most of the landscape and furnishing the plant products
which serve as our food; (2) the solid rock, so conspicuous in all
mountain ranges; (3) the hills, the valleys, and the mountains; (4) all
the streams, ponds, lakes--even the sea. If you live in a place where
man has covered up the rock and the soil evidence of geological
processes is yielded by the buildings themselves, whether they be of
stone quarried from the Earth's crust, or of brick made from clay. The
stone and brick are supported by a framework of steel originally taken
from a mine in the form of iron ore. The concrete and asphalt of the
roads came from rocks within the Earth, as did every drop of gasoline
which plays so vital a part in world affairs today. Even those
commonplaces of American life, the bottle and the "tin" can, are
products of geology. As you read this you need look only at your watch
or perhaps an item of jewelry which you wear to see something--gold,
silver, platinum, a diamond or other gem stone--which is a part of
geology.
Thus, from here it is a short step to the realization that a number of
geologic processes and agents working over long periods of time have
given rise to innumerable features and structures ranging from the
loftiest mountains down to the smallest hills and valleys; from the soil
which grows our food to the gasoline and coal which feed our industries;
from our huge iron ore deposits down to the much smaller, but now no
less significant, deposits of uranium.
How is all this related to a national park? Nowhere within our land can
the accomplishments of the great geological processes, or their
present-day operation, be seen to better advantage than in many of our
national parks and monuments. In fact, it is for this reason principally
that many of them were established. Notable is Grand Canyon National
Park, containing the most spectacular part of the Colorado's mile-deep
canyon cut during the past million or so years through a series of rocks
which themselves record a billion or more years of Earth history. Mount
Rainier is the largest volcano in the United States. On it glaciers are
now wearing away materials formerly extruded and piled up to spectacular
height by volcanic forces. Crater Lake lies in the sunken throat of a
volcano which at one time probably rivaled Rainier in size. In Carlsbad
Caverns and Mammoth Cave National Parks are two of the world's largest
caverns which clearly demonstrate the tremendous effectiveness of
subsurface water in dissolving limestone. Bryce Canyon and Zion National
Parks and the Badlands National Monument illustrated on a much smaller
but no less spectacular scale than the Grand Canyon the wonderful
erosive power of running water. In Grand Teton one can see a huge block
of the crust which has been raised thousands of feet along a high-angle
fault, and at Lassen Peak in California and Craters of the Moon in Idaho
there are exhibited some of the most recent volcanic features north of
the Rio Grande. Despite Yellowstone's wildlife and fishing it is best
known perhaps for its geysers. This brief list is by no means complete,
for something of prime geologic interest can be found in almost every
national park and monument.
Now we come to Glacier National Park. Within its boundaries there
perhaps is exhibited a greater variety of geologic features than in any
of the others. Much of the park lies above timberline so that the rocks
which comprise its mountains are exposed to view. Held within these
superb mountains is an entertaining geologic story which they are
anxious and willing to tell us. All we need to do is unlock the door
with the key the geologist gives us and then go see for ourselves. Why
do the mountains rise so precipitously above the plains? What is that
conspicuous black band across the faces of so many of the peaks, and how
did it get there? Why are some of the rocks so red? The answers to these
and other questions come out as the geologic story unfolds. The American
people are interested in this story for they realize that to understand
what they see is to increase their enjoyment thousandfold.
Chart of Geologic Time
(FOR A CHRONOLOGICAL ORDER OF EVENTS, THE CHART SHOULD BE READ FROM
BOTTOM TO TOP)
ERAS PERIODS DATES EVENTS IN GLACIER PARK AREA
CENOZOIC
The Present
Post Glacial Erosion of the mountains; formation of
alluvial fans and talus cones.
15,000 B.C.
Pleistocene Birth of modern glaciers.
Appearance of present forests.
1,000,000 B.C.
Pliocene Extensive glaciation. Formation of lakes,
waterfalls, horn peaks, cirques. Valleys
scoured deeply by glaciers.
Miocene Disappearance of forests.
Oligocene Mountains worn down, raised, eroded again.
Eocene Lewis overthrust probably occurred early
in Eocene.
58,000,000 B.C.
MESOZOIC Great mountain building (Rocky Mountain
revolution) by forces which eventually
formed Lewis overthrust. Sea withdrew and
never again returned. Thick accumulation
of marine sediments. Invertebrates
abundant in sea. Expansion of the sea.
Cretaceous
127,000,000 B.C.
Jurassic
Triassic Dinosaurs probably inhabited park and
nearby area.
182,000,000 B.C.
PALEOZOIC Seas covered region during much of era.
Permian
Carboniferous
255,000,000 B.C.
Devonian
Silurian
Ordovician
Cambrian
510,000,000 B.C.
PROTEROZOIC Sea withdrew and region was eroded at end
of era.
Area covered by sea in which Belt
sediments were deposited.
Algae lived in sea. Intrusions (diorite
sill and dikes) from flows (Purcell) of
igneous material.
ARCHEOZOIC 2,110,000,000 B.C. ?
ERAS, PERIODS, AND DATES IN THIS CHART ARE IN ACCORDANCE WITH THOSE
WHICH HAVE BEEN ADOPTED AS OFFICIAL BY THE NATIONAL PARK SERVICE.