Report Number: 21365
Reporting Year: 2001
Permit Number: CRLA-2001-SCI-0009
Date Received: Feb 28, 2002
Principal Investigator:
Katherine Wearn,
Department of Geol. Sciences,
University of Oregon, Eugene, OR
Additional investigator(s):
Dr. Katharine V.
Cashman
Park-assigned Study Id. #
CRLA-01033
Permit Expiration Date:
Dec 31, 2001
Permit Start Date:
Sep 10, 2001
Study Starting Date:
Sep 13, 2001
Study Ending Date:
Aug 10, 2002
Study Status:
Continuing
Activity Type:
Research
Subject/Discipline:
Geothermal / Volcanology
Objectives:
The main objective of this project is to
complete a detailed petrologic study of the pyroclastic obsidian produced by Mt.
Mazama's pre-climactic Cleetwood eruption. Water content analyses of the
obsidian clasts will be used to infer information about how the physical
conditions, and in particular the fragmentation level, within the conduit
evolved over the course of the eruption, as well as to develop a model of the
eruption's transition from explosive to effusive eruptive style. We will compare
the data obtained from the Cleetwood pyroclastic deposit with those from other
pyroclastic deposits associated with similar explosive-effusive eruptions,
notably the Rock Mesa eruption that occurred southwest of South Sister and the
eruption sequence that culminated in the emplacement of the Mono craters domes
in California. Analyses and comparisons of these deposits should help determine
what role obsidian plays in explosive-effusive transitional eruptions and will
cultivate a better general understanding of the physical processes that take
place in volcanic conduits.
Findings and Status:
All sample collection for this project has
been completed and data analysis is ongoing. Grainsize distributions have been
completed, and componentry analysis of the Cleetwood samples has revealed that
pyroclastic obsidian is present in significant but varying proportions
throughout the deposit. Preliminary water content analyses suggest that the
fragmentation level migrated over the course of the eruption, and that perhaps
this migration was responsible for the eruption's explosive-effusive transition.
Further FTIR analysis should help quantify the evolution of physical conditions
in the conduit over the course of the eruption, and it is anticipated that
comparison with Rock Mesa and Mono craters deposits will show that pyroclastic
obsidian is a more common product of explosive-effusive transitional eruptions
than has previously been believed, and that data collected from these clasts can
be useful in assessing some of the mechanisms involved in the eruptive process.
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
