The Geology of Crater Lake National Park, Oregon With a reconnaissance of the Cascade Range southward to Mount Shasta by Howell Williams
The Parasitic Scoria Cones of Mount Mazama
The Younger Cones
Most of this cone consists of vesicular, red-crusted dark scoria and fine ash. Bombs up to 4 feet in length are not uncommon, and many have the spindle, almond, and spiral shapes typical of lava clots blown out in a viscous condition, the form being modified in flight. Short flows of lava oozed through the scoria near the summit, and probably others account for the spurs on the sides of the cone. The crater form has been obliterated. On the ridges extending north and south from the base of the cone there are numerous fragments of scoria, but whether these were erupted from the same source or were thrown from a through-going fissure is not clear.