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Mt. Rainier has a variety of natural phenomena but the vast star-fish like system of valley glaciers is perhaps the most awe inspiring and spectacular. The center of this system lies on the higher slopes of the volcanic cone where the heavy snows of winter accumulate and compact into ice which, failing to melt under the perpetually cold Arctic-alpine climate, is forced outward and downward to the lower levels. In this process of outward movement the ice seeks the depressions as though it were water and the slender tongue-like glaciers are in some respects like rivers. The lower end or snout of each glacier remains at one place providing the ice accumulates above and pushes down fast enough to keep up with the melting but, if melting goes on faster the glacier snout must necessarily receed or move upward in its valley. All glaciers on Mt. Rainier are losing ground against the process of melting and, should this continue at the present rate the glaciers will be insufficient in a few hundred years of gone altogether in a few thousand years.
Knowing that this glacier is today gradually losing its battle for existance, we begin to speculate as to its proportions when at its maximum development. Below the snout we examine the valley so recently vacated by the ice and find that it is unlike most valleys with rivers flowing in them -- its sides are much steeper and the bottom more rounded, like the letter "U". We go down the valley a mile and find the contour of the valley does not change but the trees along the sides increase in height and diameter. We go further and the observations are the same. The truth begins to dawn upon us that in the past this glacier must have had a vastly greater development than now and that apparently a greater development than now and that apparently a great climatic transition has and is taking place. We critically examine other Mt. Rainier glaciers and find perfect consistency of evidence. Elsewhere in the park we encounter valleys now totally devoid of ice but which unmistakably show the previously observed characteristics of glaciation. The truth of the theory of widespread glaciation in this region becomes more conclusive but we begin to wonder if it was a local phenomenon or a general condition. The answer to this question is now agreed upon by students of glaciation although it was not until 183? that Louis Agassiz first suggested that ice once covered most of the northern part of North America and twenty-five years more elapsed before his theory was generally accepted. Now the evidence for the great ice age is conclusive and each year new facts are brought forth. We may go into the high mountains of western N.A. as far south as New Mexico and southern California and see many abandoned glacial valleys and other undoubtable marks of former widespread ice streams such as those which today remain on Mount Rainier. And, it has been concluded that a tremendous mass of ice once pushed out from northern Canada and did not stop in its southward march until it reached the general vicinity of the Missouri and Ohio Rivers and covered all of New England. This glacier was not of the same ice-river or valley type that we see on Mount Rainier but rather it was like the ice-cap glaciers covering greenland and Antartica today. Our knowledge of the extent and accomplishments of this great North American glacier has been gained in part by a careful study of the Greenland glacier and its effects on the land, then applying the wisdom gained to an unraveling of the story of glaciation in our own country. Hence each boulder transported by the ice from the north and left stranded on the surface of the land, each hummocky ridge, each lake, each waterfall, each scratch on the rocks--all have a meaning and together they tell the glaciation story.
Now we know that during the Ice Age glaciers of the ice-cap variety advanced over and covered parts of north-central and north-eastern United States, all of Canada east of the Rockies--not once but as many as four or five times and that between these separate advances of the ice the climate moderated and forced the glaciers back toward their northland home. In the State of Washington not only were valley glaciers numerous in the Cascade Mountains but ice bodies of great size are now known to have filled the northern part of the Puget Sound region and covered the locations of Seattle, Tacoma, and Olympia. Ice is believed to have been at least 4000 feet thick in the latitude of Seattle. Such an advance of ice from the mountains of British Columbia into the Puget Sound region is known to have occurred at least twice during the Ice Age and glaciers from Mount Rainier are thought to have pushed westward far enough to join the Puget Sound glacier--at least while the first ice was there. Neither of the Puget Sound glaciers pushed more than a few miles south of Olympia when at its maximum. Now we see that the recession of Mount Rainier glaciers add the abandonment by the ice of many valleys on the lower slopes of the Mountain does have a profound significance as far as the Ice Age is concerned. Just as northern Canada was the first gathering ground of ice which pushed southward into the United States, so likewise did the mountain areas of the West give rise to ice rivers which at their maximum may have extended as far as the lowlands. When the climate began to moderate the North American ice-cap glacier gradually withdrew to the northern regions of its origin; there it made its last stand and was finally exterminated. Likewise the valley glaciers of the mountains began to melt back to the higher regions of their beginning and now most of them are no more. Mount Rainier and other mountains of superior elevation have afforded their glaciers a unique refuge that so far has protected them from the fate of other glaciers. Hence on Mount Rainier we are really seeing the Ice Age draw to what appears to be its close. The glaciers may continue their present-day recession to a complete and permanent annihilation; or, on the other hand, we may be now experiencing one of those intervals between times of great development of glaciers and the futures may bring upon our present regions of temperate climate another deluge of ice. | ||||||
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http://www.nps.gov/mora/notes/vol11-2b.htm
17-Nov-2001
