At present, the larger glaciers of Mount Rainier are moving in the summertime at an average rate of eighteen to twenty inches per day. At the same time, they are receding about fifty feet each year, which means that about 150 feet of the ice is melting each year.
The theory has been advanced that this period of movement fluctuates over cycles of between thirty-five and forty-years. After some thirty-five years of recession, a hallance between movement, which depends on annual snow fall and melting which is result of climatic conditions is also reached, followed by another period of like time in which the glaciers gradually move down the valleys. This idea is substantiated by the fact that small lateral morains are pushed up at regular intervals and that during the last thirty years from actual observation, the glaciers have been receding, leaving a small moraine of about the same size as the series already formed. According to these facts, a predication could be made that within a few years there will be a period of greater precipitation along the northwest coast, which will result in a greater movement of the glaciers.
During the last month, the Naturalist has been placing sections of a Douglas Fir tree, 5-1/2 feet in diameter, at various points in the Park to be used as bulletin boards. This tree was 665 years old and grow at an elevation of 3100 feet. It was noticed, when counting the rings, that there were periods of rapid growth followed by periods of slower growth. These cycles were found to be uniform in distribution and of from thirty to forty years in length, a fact which throws light upon the advancement and recession of the glaciers from an interesting angle. A period of increased precipitation would cause both a faster growth of wood and movement of glaciers. Whether it can be proven or not that these periods of growth coincide with the movements of the glaciers remains to be seen. It would afford a very interesting study.
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