23891 – The Generation of Post-Caldera Rhyodacite in Crater Lake, Oregon

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

The Generation of Post-Caldera Rhyodacite in Crater Lake, Oregon


Report Number: 23891

Permit Number: CRLA-2002-SCI-0006

Date Received: Feb 26, 2003

Reporting Year: 2002

Principal Investigator: Ms Angela Roach, Department of Geological Sciences, Brown University, Providence, RI

Additional investigator(s): Dr. Malcolm Rutherford, Dr. Vicki McConnell

Park-assigned Study Id. # CRLA-00000

Permit Expiration Date: Aug 15, 2002

Permit Start Date: Aug 15, 2002

Study Starting Date: Aug 15, 2002

Study Ending Date: May 25, 2004

Study Status: Continuing

Activity Type: Research

Subject/Discipline: Geothermal / Volcanology

Objectives: It is our objective to investigate the post-caldera volcanism of Crater Lake caldera. In particular, we intend to study the generation and eruption of the rhyodacite dome magma (the youngest eruption from Crater Lake) and consider the potential for eruptions in the future. Our emphasis will be on understanding how the rhyodacite magma was generated, and if possible, place rate limits on this process. Petrographic and microprobe studies of inclusions (older rock fragments) in the Wizard Island andesite will be used to characterize the materials that were available for melting and mixing into the andesite. We may also be able to devise experiments to determine the amount and rate of melt generation from the inclusions. Additional investigations will establish the pressure, temperature, oxygen fugacity, volatile content, and conduit ascent rate of the rhyodacite magma. These data will serve as a guide to the potential for future eruptions at Crater Lake.

Findings and Status:  In the summer of 2002, we collected 37 rock samples from Wizard Island. These samples include andesite from each of the lobes of the island and examples of three types of inclusions within the andesite. We also received a suite of samples of the submarine post-caldera units from Dr. C. Bacon, USGS. We have returned both sample suites to our laboratory and have begun preparing thin sections (microscope slides) of selected samples.

For this study, were one or more specimens collected and removed from the park but not destroyed during analyses? Yes

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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