The Geology of Crater Lake National Park, Oregon With a reconnaissance of the Cascade Range southward to Mount Shasta by Howell Williams
The Glaciation of Mount Mazama
Evidence of Glaciation Outside the Caldera
The records of glaciation on the outer slopes of Mount Mazama are widespread. During the stage of maximum glaciation, ice covered all save the highest pinnacles on the divides. These were the only bare spots on an otherwise uninterrupted field of ice.
On the south and east sides of the volcano, the glaciers swept down to the base and deployed onto the flats beyond. Some of them must have been 10 miles long and ended at elevations as low as 4500 feet. On the north side, the glaciers were probably no less extensive and were confluent with those of Mounts Thielsen and Bailey. The longest glaciers, however, were those which flowed down the canyons of Castle, Copeland, and National creeks until they united in a single stream of ice in the valley of the Rogue. The snout of this composite glacier was near Union Creek Ranger Station, at an elevation of about 3400 feet. On this side of Mount Mazama, therefore, the ice spread approximately 17 miles from the summit. During this period of maximum glaciation, glaciers also covered the Union Peak volcano, and some of them served to augment the tongues of ice from Mount Mazama.