A Brief Guide to the Parapet View, Sinnott Memorial, Crater Lake National Park by John Campbell Merriam, 1938
View 2: Building of the Mountain
Two sections of the mountain are shown by finders to the right and left of this box. The one to the right is Dutton Cliff, made up of successive layers of lava and volcanic ash; the one to the left, near Discovery Point, shows a series of layers consisting of lava, volcanic ash, and glacial deposits. Specimens of the rock from each of these sections are shown in this box. Both localities may be reached by trail.The mountain in which Crater Lake rests was built by lava flows, poured out layer upon layer, and the piling up of volcanic ash, soil, deposits of streams flowing down the mountain, and materials carried by glaciers.
One can understand Crater Lake in its relation to the volcano only when the mountain is considered as result of construction extending over a long period, in which many changes took place.