The Geology and Petrography of Crater Lake National Park, 1902
LAVAS OF MOUNT MAZAMA.a
MUNSON POINT ANDESITE AREA.
For 2 miles from the crest of the rim the divide between Castle and Anna creeks is covered largely by morainal material, but andesites finally crop out in occasional cliffs and give evidence of the character of the rock beneath the surface deposits in the Munson Point area. A somewhat dacitic specimen (79) from one of the rounded ledges of this area was found by Dr. Patton to contain tridymite. To the south and southwest, beyond the main road, this andesite is covered by a large mass of basalt.