The Geology and Petrography of Crater Lake National Park, 1902
PART I.
MOUNT MAZAMA.
LAVAS OF MOUNT MAZAMA.a
BASALTS.
CRATER PEAK BASALT FLOW.
Crater Peak is the center of a small area of basalt on the divide extending south from Castle Crest and Vidae Peak between Anna and Sun creeks. The hill rises over 700 feet above the general level of the platform of andesite on which it rests. At the northern base of the hill is a mass of reddish-brown basaltic tuff. The general layer of pumice extends far up the slope, showing that, as in other cases, Crater Peak was not active after the final outburst from Mount Mazama. The pumice layer is decidedly darker than the material of which the peak (179-181) is composed. The cone is largely if not wholly fragmental, and there is no definite flow from it unless it extends to the northwest. Among the prevailing dark fragments of basalt there are occasional andesitic fragments hurled out from the underlying andesites. The summit of Crater Peak is a well-defined crater 100 yards in diameter and 25 feet deep, draining to the southwest. Some good-sized firs grow on it, and it contains a bank of snow as late as August.
