47 The Older Cones

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 Older Cones

The remains of two small cinder cones may be found on the western slopes of Mount Mazama, on the ridge overlooking Little Castle Creek. The larger of these forms the hill numbered 6236 on the geologic map (plate 3). As far as the few exposures permit judgment, the hill appears to be made up of red basaltic scoria and agglutinate. The cone, which is only about 100 feet high and less than 1/4 mile across at the base, has no trace of a summit crater. A mile to the west a still smaller accumulation of red scoria probably marks the site of a second cone.

Another ruined cone is preserved on the south side of Bear Creek, 3 miles beyond the eastern boundary of the park. Here only a few crags of red scoria remain, all traces of the original form having been obliterated by the passage of ice.

Just to the east of the Dalles-California highway, near Sand Creek crossing, there is a small, oval hillock, 150 feet high, almost completely covered by granular pumice. Poor exposures of red scoria indicate that the hillock is a denuded cone now devoid of a summit crater.


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