HR: 0800h
AN: V51D-0774    [Abstracts]
TI: Time-lapse Images of Dacite Dome Growth at Mount St. Helens, Washington, 2004–2007
AU: * Schilling, S P
EM: sschilli@usgs.gov
AF: Cascades Volcano Observatory, 1300 SE Cardinal Court, Bldg 10 Ste. 100, Vancouver, WA 98683, United States
AU: Dzurisin, D
EM: dzurisin@usgs.gov
AF: Cascades Volcano Observatory, 1300 SE Cardinal Court, Bldg 10 Ste. 100, Vancouver, WA 98683, United States
AU: Major, J J
EM: jjmajor@usgs.gov
AF: Cascades Volcano Observatory, 1300 SE Cardinal Court, Bldg 10 Ste. 100, Vancouver, WA 98683, United States
AU: Moran, S C
EM: smoran@usgs.gov
AF: Cascades Volcano Observatory, 1300 SE Cardinal Court, Bldg 10 Ste. 100, Vancouver, WA 98683, United States
AU: Gooding, D J
EM: dgooding@usgs.gov
AF: Cascades Volcano Observatory, 1300 SE Cardinal Court, Bldg 10 Ste. 100, Vancouver, WA 98683, United States
AU: Poland, M P
EM: mpoland@usgs.gov
AF: Hawaiian Volcano Observatory, 1 Crater Rim Drive Hawaiian Volcano National Park, Hilo, HI 96718, United States
AB: Fixed-position, digital cameras of varying type have been used to record the growth and changing morphology of a dacite lava dome at Mount St. Helens since the onset of extrusion in October 2004. Dome growth involves extrusion of a solidified lava plug at rates, determined from sequential digital elevation models derived from vertical aerial photographs, that have declined from 6 m³/s in late 2004 to 0.3 m³/s in early 2007. Time- lapse images at 1-10 megapixel resolution have been acquired at rates of 1-60 frames per hour over periods of several hours to nearly three years. Images were taken at camera sites established on the crater floor, crater rim, 1980-1986 lava dome, and currently active dome. In addition to recording the physical changes of the growing dome and its dramatic effect on a surrounding glacier, the cameras have captured seismogenic rockfalls, slumps, and small explosions. Quantitative analysis of the oblique images requires epipolar equations to calculate coordinates of mobile points that are visible from two or more cameras to yield three-dimensional surface displacements that are consistent with displacements measured by other means (for example, GPS and short duration photographic sequences at known scale) and with the generally declining extrusion rate. Although extrusion has been continuous, the photographs show episodes of strong differential motion within an extruding plug and several short pauses, at least two of which had coincident occurrences of relatively large (magnitude 3) earthquakes when motion resumed. Several observations from the photographs are consistent with a proposed stick-slip model of plug motion (Iverson and others, Nature, 23 November 2006), but many observations are not at sufficient frequency to discriminate between periodic and continuous plug motion.
UR: http://vulcan.wr.usgs.gov/home.html
DE: 8414 Eruption mechanisms and flow emplacement
DE: 8419 Volcano monitoring (7280)
DE: 8429 Lava rheology and morphology
DE: 8485 Remote sensing of volcanoes
DE: 8494 Instruments and techniques
SC: Volcanology, Geochemistry, Petrology [V]
MN: 2007 Fall Meeting