James L. Dyson

“ Despite recent rapid shrinkage of glaciers and the disappearance of some, Glacier National Park still is a land of ice, yet when the visitor views its present day glaciers and its sublimely beautiful mountain scenery he should not be unmindful of the powerful forces which, working during many thousands of years, have brought it all about. ”

“ 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. ”

“ When sufficient snow is added to the upper part of the glacier to cause the ice at the front to move forward equal to the rate at which it melts away, the glacier is in equilibrium with the climate. When the yearly added snow decreases in amount the ice front seems to retreat or move back, whereas the mass of the glacier is merely decreasing by melting on top and along the edges, just as a cube of ice left in the kitchen sink decreases in size. ”

“ It is at this site that plucking is most dominant because water enters by day and freezes in the rock crevices at night. This quarrying headward and downward finally results in the formation of a steep-sided basin called a cirque or glacial amphitheatre. Because the cirque is the first place that ice forms and the place from which it disappears last, it is subjected to glacial erosion longer than any other part of the valley. Thus its floor is frequently plucked and scraped out to a comparatively great depth so that a body of water known as a cirque lake forms after the glacier disappears. ”

“ Although several thousand years have been required for their formation most talus accumulations in the park are still actively growing, especially in spring and early summer when rocks are pried loose by the alternate freezing and thawing of moisture within fractures. The artillery-like crack made when a falling rock crashes to the base of a high cliff is a familiar sound to anyone who has spent much time in the mountains. ”

“ Despite this magnificence the visitor must soon turn his attention to the tremendous accumulation upon which he stands, for it is no less interesting than the mountains and lakes. Among the many 25 boulders which lie along the path are two prominent limestone blocks each 10 to 15 feet in diameter. The underside of one was grooved and polished as the ice pushed it across the rock surface underlying the glacier. The other, partially embedded in the moraine, has a polished upper surface because the glacier flowed over it for a time. ”

“ Innumerable loose slabs of red rock along the side of the road contain excellent mud cracks and ripple marks. Near Avalanche creek on the west side of Logan Pass the highway crosses the Grinnell where it comes to the surface on the western limb of the big syncline.
The formation is well exposed in the vicinity of Sperry Chalet and Glacier. It forms all the mountains surrounding the basin in which the chalet is located, and the trail from chalet to glacier lies wholly on it. At the glacier intensely folded white quartzite layers and red argillites are very conspicuous. ”

“ As a matter of fact, there are persons who visit Glacier National Park without seeing a single glacier, while others, although they actually see glaciers, leave the park without realizing they have seen them. This is because the highways afford only distant views of the glaciers, which from a distance appear much like mere accumulations of snow. A notable example is Grinnell as seen from the highway along the shore of Sherburne Lake and from the vicinity of the Many Glacier Entrance Station. ”

“ Its edge was bordered by a ridge-like moraine nearly a hundred feet high. Today, the trail from Logan Pass to Hidden Lake skirts the outside edge of the moraine. Should the hiker leave the trail and climb the few yards to the top of this moraine he could see it stretched out before him as a giant necklace encircling the base of Clements Mountain, but between mountain and moraine, where a few years ago the glacier lay, he will see only bare rock or drifted snow. ”

“ We know that the processes of erosion and weathering will continue, that alluvial fans and talus cones will grow larger, and gorges will be eroded deeper, and as a result the mountains will be cut down to lower elevations. But, as we have seen, this event will require much time. If the present climate continues for a few more years our remaining glaciers 24 will disappear, but there is nothing in geologic history which says they won’t return again, possibly even to the size of their heyday in the Pleistocene. ”

“ As the ice moves it continually breaks rock fragments loose. Some of these are ground into powder as they move against each other and against the bedrock under the glacier. Most types of rock, especially the limestones and shales on which the Park glaciers rest, when ground fine enough yield a gray powder. All melt-water streams issuing from glaciers are cloudy or milky from their load of this finely ground “rock flour.”
Water from Grinnell Glacier is so laden with rock flour that the small lake along the edge of the ice into which the water pours is nearly white. ”

“ But certain breeds of man are the only despoilers of mountains that we need fear, so if the good citizens of our land keep the human invader and his dams and earth-moving equipment out of our national parks these grand mountains will endure for many thousands, yes, even millions of years. ”

“ Mud cracks, ripple and current marks, raindrop impressions, and other 8 features made while the sediments were accumulating are common. The red color is due to abundant iron oxide occurring mainly as a cement between the sand and mud grains. All the rocks of Glacier Park contain some iron, or rather contain iron-bearing minerals. These minerals have various colors unless they have been oxidized, in which case the color is red or brown. Oxidation of the Grinnell formation probably took place while the mud was accumulating and during those periods when it was exposed to the atmosphere. ”

“ The snowline is the level above which more snow falls in winter than can be melted or evaporated during the summer. On mountains which rise above the snowline glaciers usually occur. The snowline is an elusive feature and can be seen only in late summer. For example, during the latter part of June snow extends from the summits of most Glacier National Park mountains down their slopes to timberline, and some snowbanks extend even lower. ”

“ Siyeh is the only other regularly visited Park glacier. It lies about half a mile beyond the end of the Cracker Lake trail, and can be reached from that point by an easy walk through grassy meadows and a short climb over a moraine. Siyeh, however, is less spectacular than either Grinnell or Sperry, being much smaller and lacking crevasses, so common on the other two. Few people make the spectacular trail trip over Siyeh Pass but those who do may visit Sexton Glacier by making a short detour of less than half a mile where the trail crosses the bench on which the glacier lies. ”

“ In most places these rocks are covered by glacial moraine, but they are exposed along the highway from Babb into the Swiftcurrent Valley, especially along the shore of Sherburne Reservoir and near the entrance station. Because these shales readily disintegrate when exposed to the atmosphere they give rise to slumps and landslides which, although of small proportions, cause a great deal of damage to the highway, sections of which must be rebuilt annually. At most damaged spots along the route the shales appear as a dark mud or clay in the roadcuts. ”

“ As the former long valley glaciers enlarged their cirques by cutting farther in toward the center of the range, the latter finally was reduced to a very narrow steep-sided ridge, the arete. The imposing height of the Garden Wall can readily be determined by using the layer of diorite as a scale. The conspicuous black band formed by the edge of this layer has an average width of 75 feet. So, from the porch of the Many Glacier Hotel a Park visitor can readily see that the Garden Wall, even though five miles distant, is about 4,200 feet high. ”

“ Next above the Grinnell is a thick limestone formation which, because of its weathered buff color, stands out in sharp contrast to the red beds upon which it rests. It is the greatest cliff-maker in the park and in several places its entire thickness of 4,000 feet may be exposed in a single nearly vertical cliff. Since it is younger than the three preceding formations, it is confined mainly to the higher elevations, capping many of the loftiest peaks within the Lewis and Livingstone Ranges. ”

“ The thicker a stream of ice, the more erosion it is capable of performing; consequently, the main valley becomes greatly deepened, whereas the smaller glacier in the tributary valley does not cut down so rapidly, leaving its valley hanging high above the floor of the major valley. ”

“ 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. ”

“ Ice within these glaciers moves slowly. The average rate in the smallest ones may be as low as 6 to 8 feet a year, and in the largest probably 25 to 30 feet a year. There is no period of the year when a glacier is motionless, although movement is somewhat slower in winter than in summer. Despite the slowness of its motion the ice, over a period of years, transports large quantities of rock material ultimately to the glacier’s end where it is piled up in the form of a moraine. ”

“ These younger layers are Cretaceous shales and sandstones underlying the plains immediately east of the mountains. The mountains themselves have been carved by streams and glaciers from the Belt formations comprising the upper block of older rock, that slice of the crust which has been moved more than 15 miles toward the east. The surface over which it was pushed is the Lewis overthrust. At the time this great break occurred the part of it now exposed in Glacier National Park was deeply buried. ”

“ Several of the glaciers, however, are accessible by trail and are annually visited by many hundreds of people, either on foot or by horse. Most accessible of all Park glaciers is Grinnell. It can be reached by a six-mile trip over an excellent trail from Many Glacier Hotel or Swiftcurrent Camp. Sperry, likewise, can be reached by trail, although the distance is several miles greater than in the case of Grinnell. The trip, 6 however, can be broken and possibly made more interesting by an overnight stop at Sperry Chalet, which is located about three miles from the glacier. ”

“ A few species, among which are the alpine willows, driven southward from the far north during the Pleistocene period still persist at high altitudes but they are always ready to move down into the valleys if the 21 climate should again become cool. Of course, continued warming would cause them to disappear. After the large Pleistocene streams of ice disappeared there followed a period of about 5,000 years during which the climate was somewhat warmer and drier than at present, conditions under which even very small glaciers could not have survived. ”

“ As the surface of the glacier, except that insulated by the debris, is lowered by melting, the mounds form and grow gradually higher until the debris slides from them, after which they are 7 speedily reduced to the level of the rest of the surface. They are seldom higher than 3 or 4 feet.
A glacier table is a mound of ice capped, and therefore protected from melting, by a large boulder. ”

“ Dyson worked as a ranger-naturalist in Glacier National Park for eight summers starting in 1935.
[2] Argillite is the term used by geologists for a rock, originally a shale, which has been recrystallized or made harder by greater pressure. In external appearance it looks like shale.
[3] A dike is like a sill in all respects except that it cuts across adjacent layers instead of paralleling them.
[4] For a complete discussion of glaciers and their effects see Special Bulletin No. 2 (Glaciers and Glaciation in Glacier National Park) of the Glacier Natural History Association. ”

“ Its history is similar to that of the debris cone. After a time the boulder slides off its perch, and then the mound of ice melts away.
Snow which fills crevasses and wells during the winter often melts out from below, leaving thin snowbridges in the early part of the summer. These constitute real hazards to travel on a glacier because the thinner ones are incapable of supporting a person’s weight. This is one very good reason why the inexperienced should never venture onto the surface of a glacier without a guide. ”

“ 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 ”

“ It is probable that the Park glaciers are not remnants of the large glaciers present during the Ice Age which terminated approximately 10,000 years ago, because it is known that several thousand years after that time the climate of the Glacier National Park region was somewhat drier and warmer than now. ”

“ The algae colonies are in the form of rounded masses up to several feet in diameter and bear a crude resemblance externally and internally to a head of lettuce or cabbage. Geologists know these algae by the genus name Collenia. Because of the rounded and smoothed surfaces on these colonies, mountain climbers frequently find the reef difficult to cross. ”