HR: 0800h
AN: V21A-0391    [Abstracts]
TI: Effect of Input Parameters on a Lava Flow Emplacement Model. Application to the 1999-2002 Lava Flow of Santiaguito, Guatemala.
AU: * Avard, G
EM: gar2f@mizzou.edu
AF: University of Missouri-Columbia, 101 Geological Sciences, Columbia, MO 65211-1380, United States
AU: Whittington, A G
EM: whittingtona@missouri.edu
AF: University of Missouri-Columbia, 101 Geological Sciences, Columbia, MO 65211-1380, United States
AU: Harris, A J
EM: harris@higp.hawaii.edu
AF: Hawai`i Institute of Geophysics and Planetology, University of Hawai`i at Manoa Hawai`i Institute of Geophysics and Planetology 1680 East-West Road, POST 602, Honolulu, HI 96822, United States
AB: The emplacement of a lava flow depends on external conditions such as effusion rate, topography, and ambient temperature, as well as on the characteristics of the lava such as chemical composition, crystal content, vesicularity, core temperature, crust thickness, etc. Hence these input values control the quality of any modeling. Where most of these variables are known, it may be possible to constrain an unknown factor if the final emplacement history is known. Here we explore the application of this technique to determining extrusion rates at the active dacitic Santiaguito lava dome complex, Guatemala. Caliente is the current active dome with continuous growth through an extrusive lava front and frequent ash explosions Like the other domes, it presents some more effusive periods of activity such as the 4 km long lava flow (1999-2004). Experimental measurements suggest a viscosity about 10⁸ to 10⁹ Pa.s in the range of temperature 850 to 800°C for fully remelted dacites. Actual viscosities will be around 10 times higher due to the crystal content, estimated to be 40% (including 30% phenocrysts), almost exclusively plagioclase. Calculations and petrographic observations indicate that crystallinity remains constant within the flow. The vesicularity is about 9 volume %. Using the FLOWGO model (Harris et al., 2001 Bull Volc), we predict that eruption temperatures must exceed 835°C in order for long flows to form (i.e. to at least reach the base of the dome edifice). The calculated extrusion rate is then in the range of 0.8 to 1.6 m3.s^-1 which is consistent with the observed values between 2001 and 2002 (Harris et al., 2004 JVGR).
DE: 8400 VOLCANOLOGY
DE: 8414 Eruption mechanisms and flow emplacement
DE: 8425 Effusive volcanism
DE: 8429 Lava rheology and morphology
DE: 8486 Field relationships (1090, 3690)
SC: Volcanology, Geochemistry, Petrology [V]
MN: 2007 Fall Meeting