The Geology and Petrography of Crater Lake National Park, 1902
PART I.
MOUNT MAZAMA.
LAVAS OF MOUNT MAZAMA.a
BASALTS.
TIMBER CRATER BASALT FLOW.
Timber Crater, 5 miles northeast of Crater Lake, is the peak next in size to Scott Peak. It rises 1,500 feet above the surrounding plain and has a somewhat eccentric conical form with gentle slopes covered largely, to an elevation of 6,700 feet, by pumice from the final eruption of Mount Mazama. At 6,900 feet a reddish vesicular flow of basalt (165) issued from the southwest slope.
Another basalt stream forms a prominent spur to the northwest. The lava is fresh, with all the peculiarities of a recent flow. Above this point the slope is made of lapilli, with a light covering of pumice. That the upper portion of the mountain is a cinder cone is not seen by the traveler until he reaches the summit, where there is a well-defined crater 50 feet deep and 250 yards in diameter. The crater is double, or rather there are two craters of equal size side by side. One is nearly north of the other, and the two were most likely active at different times. With the progress of the eruption the vent shifted slightly parallel with the range. This is a common feature in many volcanic fields, but is rather unusual in the Cascade Range. The coating of pumice from Mount Mazama is spread upon the slopes of the cinder cone of Timber Crater, showing that its activity had closed before that of Mount Mazama.
The view of Crater Lake and its rim from Timber Crater is especially fine, and to the northward Mount Thielsen, the “lightning rod” of the Cascade Range, sometimes also called the “Matterhorn” of the range, stands out conspicuously.
