The Geology of Crater Lake National Park, Oregon With a reconnaissance of the Cascade Range southward to Mount Shasta by Howell William
Cinder Cones and Associated Flows
Cones Bordering Pumice Flat
The cinder cones near the east base of the Union Peak volcano are located on a fissure radiating from the former summit of Mount Mazama. Although this is taken to mean that they were fed from the reservoir beneath Mount Mazama, their products are similar to those of the older Union Peak volcano. In other words, they are olivine-bearing basaltic andesites varying in texture from hyalopilitic through intergranular to subophitic.