Open-File Report O-08-03 PRELIMINARY GEOLOGIC MAP OF THE SURVEYOR MOUNTAIN 7.5’ QUADRANGLE, KLAMATH COUNTY, OREGON
The Surveyor Mountain 7.5 minute quadrangle has as its focal point two large composite volcanoes, both Pliocene in age, that have been transected by a series of northwest-southeast trending normal faults. Buck Mountain and Surveyor Mountain were built over tens of thousands of years by eruptions of pyroclastic material, ash, cinders, and bombs, and extrusions of relatively fluid lava of a basaltic andesite composition. Anyone who has driven the Rim Road at Crater Lake National Park and has viewed Wizard Island or Llao Rock has viewed first-hand what the cross-section of a composite volcano looks like. This quadrangle occupies predominantly high terrain between the Johnson Prairie to the west and Spencer Creek to the east.
by Stanley A. Mertzman, Matthew Reuer and Benjamin Schiffer