The Glacial History of an Extinct Volcano, Crater Lake National Park

Abstract

Alternating layers of lava and glacial material in the rim surrounding Crater Lake record the history of an intermittently active volcano on the slopes of which glaciers formed during periods of dormancy, to be destroyed when igneous activity resumed. The position of buried moraines and the pumice character of material mantling the glacial topography indicate that Mount Mazama disappeared as the result of collapse. The glacio-volcanic sequence discovered at Crater Lake is particularly significant in that it throws light upon the history of the volcanoes of the Northwest which may be similar to that of Mount Mazama before its destruction.