12720 – Volcanic Evolution of the Crater Lake Region

Investigator’s Annual Reports (IAR’s) for Crater Lake National Park

Volcanic Evolution of the Crater Lake Region


Report Number: 12720

Reporting Year: 1992

Permit Number: CRLA1992ADOS

Current Status: Checked in

Date Received: Jan 01, 1998

Principal Investigator: Charles Bacon, U.S. Geological Survey, Menlo Park, CA

Park-assigned Study Id. # CRLA1992ADOS

Permit Expiration Date: Jan 01, 1998

Permit Start Date: Jan 01, 1998

Study Starting Date: Jan 01, 1992

Study Ending Date: Jan 01, 1992

Study Status: Completed

Activity Type: Other

Subject/Discipline: Geology / General

Objectives: To document the growth and evolution of Mount Mazama, the volcanic complex in which Crater Lake caldera lies, in order to define processes that led to accumulation of a large volume of silicic magma in the upper crust. Secondary goals are to further knowledge of catastrophic eruptions, such as the one that resulted in the collapse of the caldera.

Findings and Status:  Five sets of lavas and pyroclastic rocks, each of which represents a comparatively short episode of activity, have been distinguished in the caldera wall between Kerr Notch and Garfield Peak; all five are also exposed on the south flank of Mount Mazama. Most of the area southwest of highway 62 was mapped during an intense, three-week field season. This rarely frequented region contains several volcanic centers, at least one of which erupted beneath glacial ice. Many of the small hills are the glaciated cores of former cinder cones. In the field we were able to distinguish lava flows from different cones on the basis of their phenocryst contents. On either side of Castle Point are some of the youngest basaltic vents in the park. These apparently were active during a short interval between deglaciation and the climactic eruption, and produced rather primitive tholeiitic basalt.

For this study, were one or more specimens collected and removed from the park but not destroyed during analyses? No

Funding provided this reporting year by NPS: 0

Funding provided this reporting year by other sources: 0

Full name of college or university:  n/a

Annual funding provided by NPS to university or college this reporting year: 0



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