GLACIER Glaciers and Glaciation in Glacier National Park Special Bulletin No. 2

GLACIERS AND GLACIATION IN GLACIER NATIONAL PARK
By
James L. Dyson
Head, Department of Geology and Geography
Lafayette College
Member, Research Committee on Glaciers
American Geophysical Union*

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*Dr. Dyson worked as a ranger naturalist in Glacier National Park for eight different summers starting in 1935. During that time he undertook special research on park glaciers in addition to his regular assignments.

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The glaciers of Glacier National Park are only a few of many thousands which occur in mountain ranges scattered throughout the world. Glaciers occur in all latitudes and on every continent except Australia. They are present along the Equator on high volcanic peaks of Africa and in the rugged Andes of South America. Even in New Guinea, which many think of as a steaming, tropical jungle island, a few small glaciers occur on the highest mountains.

MAJOR GLACIERS OF GLACIER NATIONAL PARK

Almost everyone who has made a trip to a high mountain range has heard the term, "snowline," and many persons have used the word without knowing its real meaning. The true snowline, or "regional snowline" as the geologists call it, 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 the month of June snow extends from the summits of most Glacier National Park mountains down their slopes to timberline, and some snowbanks extend even lower. At that time snowline appears to be down near timberline. But as the summer progresses and higher temperatures melt the lower-lying snowbanks this apparent snowline retreats higher and higher up the slopes, until late August or early September, when most of the park mountains are devoid of snow. Then we know that here the regional snowline actually lies above the summits of most peaks, at a height of more than 10,000 feet. The only parts of the United States which project above the regional snowline are the highest summits in the Cascade Range in California, Oregon and Washington, and in the Olympic Mountains in the latter State.

MT. OBERLIN CIRQUE AND BIRD WOMAN FALLS

The Olympic area is unique, for here the regional snowline descends to about 6,000 feet, lower than anywhere within the boundaries of the Continental United States. Extraordinarily heavy annual snowfall and the high percentage of cloudy weather, which retards the melting of snow, combine to depress the snowline to such a low level.