12806 – 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: 12806

Reporting Year: 1997

Permit Number: CRLA1997ASPA

Date Received: Jan 01, 1998

Principal Investigator: Charles Bacon, U.S. Geological Survey, Menlo park, California

Park-assigned Study Id. # CRLA1997ASPA

Permit Expiration Date: Jan 01, 1998

Permit Start Date: Jan 01, 1997

Study Starting Date: Jan 01, 1997

Study Ending Date: Jan 01, 1997

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 an 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:  Work continues on preparation of the 1:24,000 scale geologic map for publication. Digital files of the geologic map nd all eleven geologic panoramas of the caldera walls are being edited in ArcInfo. These will be published in color. A volcano and earthquake hazards assessment of the Crater Lake area was published in cooperation with USGS colleagues at the Cascades Volcano Observatory. A poster on this subject was presented at the 1997 General Assembly of the International Association of Volcanology and Chemistry of the Earth’s Interior in Puerto Vallarta, Mexico. The hazard report contains information on probability of future volcanic eruptions, the types of volcanic events that may occur, hazard zones for different kinds of volcanic activity, potential for earthquakes on the West Klamath Lake fault zone (which passes within 1 km of Rim Village) and other faults, and possible consequences of earthquake shaking, including landslides from the caldera walls and waves generated on Crater Lake. Also published in 1997 was a major paper on primitive magmas at Crater Lake and four other Cascade volcanic centers. Renee Bourgeois, University of Oregon, began a Masters thesis project on the Cleetwood pumice fall deposit under the direction of Prof. K.V. Cashman and C.R. Bacon. Duane Champion (USGS, Menlo Park) and Bacon, assisted by Bourgeois, collected approximately 60 oriented 1″ diameter core samples of the lava flows and dome of the subglacially-erupted Bear Bluff complex, west of Annie Creek, for paleomagnetic study in Menlo Park. Preliminary results indicate rhyodacite and andesite of this complex record the same paleomagnetic direction, a finding consistent with field observations that imply both magma types were erupted concurrently.

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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