HR: 1340h
AN: V53D-1589    [Abstracts]
TI: Photogeologic Mapping of the 2004-2005 Mount St. Helens Eruption
AU: * Herriott, T M
V53D-1589 AF: Department of Geological Sciences, University of California, Santa Barbara, CA 93106 United States
AU: Pallister, J S
EM: jpallist@usgs.gov
AF: USGS Cascades Volcano Observatory, 1300 SE Cardinal Court, Suite 100, Vancouver, WA 98683 United States
AU: Vallance, J W
V53D-1589 AF: USGS Cascades Volcano Observatory, 1300 SE Cardinal Court, Suite 100, Vancouver, WA 98683 United States
AB: The 2004-05 eruption of Mount St. Helens has consisted mainly of lava dome extrusion, producing a series of near-solid, fault gouge-mantled spines. Stereo aerial photographs taken approximately every 2-4 weeks along with visual observations and oblique photographs taken from aircraft and nearby observation points, aided in compilation of photogeologic maps of the dome. Twelve maps cover the period from 1 October, 2004, through 10 August, 2005, and document the development of six spines: an initial small vertical spine and N-S elongated wall of dacite, two large and elongate spines ("whalebacks") and two smaller near-vent spines. All spines rose from the same general vent area near the southern margin of the 1980-86 lava dome. The photogeologic maps also show the progression of deformation affecting the crater glacier, distribution of small avalanche deposits, and distribution of ash on the crater floor from phreatic and phreatomagmatic eruptions of 1-5 October, 2004, and 8 March, 2005. The maps are used to track geographic features in the rapidly changing crater and to provide context for dome, gouge, and ash samples to changing positions in a dynamic environment where spines extrude, deform, decrepitate, and are over run by new material.
DE: 3690 Field relationships (1090, 8486)
DE: 8400 VOLCANOLOGY
SC: Volcanology, Geochemistry, Petrology [V]
MN: Fall Meeting 2005