Report Number: 12846
Reporting Year: 1999
Permit Number: CRLA199902-004
Date Received: Jan 01, 2000
Principal Investigator:
Charles R. Bacon,
U.S. Geological Survey,
U.S.G.S.,
Menlo park, CA
Additional investigator(s):
Duane Champion
Park-assigned Study Id. #
CRLA199902-004
Permit Expiration Date:
Jan 01, 2005
Permit Start Date:
Jan 01, 2000
Study Starting Date:
Jan 01, 1979
Study Ending Date:
Jan 01, 2005
Study Status:
Completed
Activity Type:
Research
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: The 1:24,000
scale geologic map of Mount Mazama and Crater Lake caldera is being prepared for
publication. Digital files of the geologic map and all eleven geologic panoramas
of the caldera walls have been completed in ArcInfo. Geologic unit descriptions
will be completed in 2000. These will be published in color and the map also
will be released in digital form. A paper on the slip rate on the West Klamath
Lake fault zone near Crater Lake was published in the journal, "Geology". Dr.
Charles Mandeville, American Museum of Natural History, continued working on on
sulfur isotope determinations in volcanic rocks from Crater Lake in order to
elucidate processes of gas loss from Mount Mazama prior to and during volcanic
eruptions. Dr. Marvin Lanphere, USGS, and co-workers measured several new K-Ar
and Ar-Ar ages of volcanic rocks from Carter Lake. These data will be published
in a companion paper to the geologic map. A significant new finding resulted
from ion microprobe U-Pb and U-Th dating of zircon from granitic blocks ejected
in the caldera-forming eruption. These results, presented at the Fall Meeting of
the American Geophysical Union and submitted for publication in Geology,
indicate that the shallow pluton from which the blocks were derived was intruded
beneath Mount Mazama approximately 110,000 years ago. Field work in 1999
consisted of sampling lava from Scoria Cone for paleomagnetic determinations and
providing advice to Dr. Mandeville on sample sites for his study.
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
