Part 1

Produced by Stephen Hutcheson and the Online Distributed Proofreading Team at http://www.pgdp.net

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

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.

The Story Begins

The most striking feature of the mountains--certainly the one which comes first to a visitor's attention--is the color banding. No matter where one looks this feature greets his view. If he enters the park at the St. Mary Entrance, there ahead on the sides of Singleshot and East Flattop Mountains are white and purple bands. Should he enter first the Swiftcurrent Valley, he would soon note the banding in the mountains lying to his right and left, and finally culminating in the precipitous Garden Wall at the head of the valley. The visitor soon realizes that every mountain within the park is composed of rock layers of various colors. With very few exceptions these strata are of sedimentary origin; that is, they accumulated by depositions of muds and sands in a body of water and are now mainly limestones, shales, and sandstones. These sedimentary rocks all belong to a single large unit known as the Belt series, so named because of exposures in the Little Belt and Big Belt Mountains farther south in Montana. In Glacier National Park these rocks, which have a maximum thickness of more than 20,000 feet, are in the form of a large syncline (downfold), the east and west edges of which form the crests of the Lewis and Livingstone Ranges (Figure 3D). Throughout the large area of western Montana, northern Idaho, and southern British Columbia where Belt rocks occur, they are important mountain-makers. In addition to the ranges already mentioned they are the principal rocks in many others, including the Mission, Swan, and Flathead in the region south of Glacier Park; the Bitterroot and Coeur d'Alene between Idaho and Montana; and the Purcell in British Columbia. Further, rocks of similar age form the core of the Uinta Range in Utah and the lower section of the Grand Canyon in Arizona.

During the Proterozoic Era of Earth history a long, narrow section of North America extending from the Arctic Ocean southward, probably as far as Arizona and southern California, slowly sank to form a large, shallow, sea-filled trough known as a geosyncline (Figure 1). Streams from adjacent lands carried muds and sands into the sea, at times almost completely filling it. Inasmuch as thousands of feet of sediments were deposited, the geosyncline must have continued to sink throughout the period of sedimentation. Eventually the muds were compacted into shales, or limestones if they contained a lot of lime, and the sands into sandstones. These are the rocks we now know as the Belt series. The surfaces of many of the sandstone layers are covered with ripple marks which could have been made only by wave and current action in shallow water. Mudcracks on many of the shale beds prove that at times the sediments, probably near the mouths of rivers were exposed to the air long enough to dry out. Great thicknesses of limestone and numerous fossils of calcareous algae, primitive marine plants, are evidences that the body of water was a sea.

FIGURE 1. BELT GEOSYNCLINE

Throughout the geologic past the appearance and disappearance of seas on the continents have been frequent events. In fact such changes are slowly taking place even today. Hudson Bay and the Baltic and North Seas are examples of shallow seas situated on the continents. The area around Hudson Bay is rising; as attested by the fact that some of the fish weirs constructed in water along the shore during the past several hundred years are now a considerable distance inland. We know also that our Atlantic coast has been subsiding for a number of years at an annual rate of about 0.02 feet. To be sure, these movements are slow, but if continued over a long period they might conceivably make some rather profound changes, even as the birth and death of the Belt sea.

Within Glacier National Park the Belt series is divided on the basis of lithologic differences into six distinct formations. Because each has a characteristic color, these formations can easily be identified, often from distances of several miles. Usually two, sometimes three or four, of them comprise a single mountain, the oldest always at the mountain base and the youngest on the summit, this being the relative position in which they were deposited in the form of sediment.

The Belt Formations

ALTYN FORMATION.

This is the oldest of the several formations and thus occupies a stratigraphic position at the base of the entire series. It is composed mainly of sandy dolomites (magnesian limestones) and limestones which weather to a light buff color. It outcrops all along the base of the eastern front of the Lewis Range and comprises the entire block of Chief Mountain. Because of its comparatively great resistance to weathering and erosion it usually forms a conspicuous ridge or terrace wherever it crosses a valley. In the Swiftcurrent Valley it forms the dam which holds in Swiftcurrent Lake and creates Swiftcurrent Falls. In Two Medicine Valley the highway crosses a similar terrace which gives rise also to Trick Falls. In the St. Mary Valley it creates the Narrows and forms the imposing wall in lee of which East Glacier Campground is located. The rock of this formation can best be examined on the ridge immediately east of Many Glacier Hotel (between hotel and parking lot) and above Swiftcurrent Falls. Its average thickness is about 2,300 feet.

APPEKUNNY FORMATION.

Lying on top of the Altyn are 3,000 or more feet of prevailing greenish shales and argillites comprising the Appekunny formation. Slabs of these rocks, because of their great hardness, have been used as flagstones in the walks at the Many Glacier Ranger Station and adjacent Park Service residential area. Mud cracks and ripple marks are common. The formation is prominent on the side of Singleshot Mountain near the St. Mary entrance to the park, and everywhere immediately overlying the lighter-hued Altyn along the east edge of the Lewis Range where, especially when seen from a distance, it appears to have a purplish color. It also outcrops along the western base of the Livingstone Range (Figure 3D), but such exposures are as a rule obscured by a cover of dense forest. Accessible outcrops can readily be examined along Going-to-the-Sun Highway for several miles east of Sun Point and near McDonald Falls, and also along the lower part of the Grinnell Glacier trail.

GRINNELL FORMATION.