HR: 17:45h
AN: P34A-08    [Abstracts]
TI: Lava Flow Emplacement at Pillan, Io in 1997: Implications for Massive Basaltic Flow Emplacement on Earth and Mars.
AU: * Davies, A G
EM: Ashley.Davies@jpl.nasa.gov
AF: JPL, ms 183-501, 4800 Oak Grove Drive, Pasadena, CA 91109, United States
AU: Wilson, L
EM: L.Wilson@lancaster.ac.uk
AF: Lancaster University, Environmental Science Department, Lancaster, LA1 4YQ, United Kingdom
AU: Keszthelyi, L
EM: laz@usgs.gov
AF: USGS-Flagstaff, Astrogeology Branch, 2255 N. Gemini Road, Flagstaff, AZ 86001, United States
AU: Williams, D A
EM: David.Williams@asu.edu
AF: Arizona State University, School of Earth and Space Exploration, Box 871404, Bateman Physical Sciences F506B, Tempe, AZ 85287, United States
AB: Only two bodies in the Solar System currently exhibit high-temperature volcanic activity: the Earth, and the Jovian satellite, Io. Massive flow emplacement has played a significant role in the volcanic history of both Earth and Mars. The largest lava flows on Earth by volume in historic times were emplaced at Laki, Iceland, in 1783-84. These flows were dwarfed by the flows emplaced at Pillan, Io, in 1997, which may be the largest effusive eruption ever witnessed. At least 31 km³ of lava were erupted in ~100 days [1] with an additional 25 km³ erupted shortly thereafter, yielding a total of 56 km³ [2]. In addition to the lava flows, a pyroclastic deposit of unknown thickness covering over 125,000 km² was laid down. This eruption is particularly important as it sheds light on the emplacement of very large, voluminous flows that were emplaced millions of years ago on Earth (flood basalts) and also on Mars. Temporal and areal constraints allow application of models of varying effusion rate [3] to determine peak effusion rate, and also the varying rate of surface coverage. From this information, thermal emission profiles have been constructed that show that the thermal emission measured by the Galileo Near Infrared Mapping Spectrometer (NIMS) [e.g., 4] can be produced by insulated flows, implying that turbulent flow emplacement was probably not the dominant emplacement regime. Peak effusion rates at Pillan most likely exceeded 10⁴ m³ s^-1. The resulting insulating crust, with a small crack fraction, appears to be similar to that on terrestrial flood basalts that formed inflated sheet flows with a 'rubbly' surface [5]. Our new results from analysis of the Pillan data lend additional quantitative support to the idea that terrestrial rubbly pahoehoe flows and Martian "platy-ridged" flows are diagnostic of similar high eruption rates [5]. Additionally, NIMS thermal emission measurements can be reproduced with a basaltic, rather than ultramafic, magma composition. We note that even more extensive flow fields are seen on Io. Lei Kung Fluctus has an area of 1.25 x 10⁵ km². This work was carried out at the Jet Propulsion Laboratory-California Institute of Technology, under contract to NASA. AGD is supported by a grant from the NASA PG&G Program. References: [1] Williams, D.A. et al. (2001) JGR, 106, E12, 33,105-33,119. [2] Davies, A. G. et al. (2006) LPSC 37, abstract 1155. [3] Wadge, G. (1981) JVGR, 11, 139-168. [4] Davies, A. G. et al. (2001) JGR, 106, E12, 33079-33104. [5] Keszthelyi, L. et al. (2004) G3, 5, 2004GC000758.
DE: 5480 Volcanism (6063, 8148, 8450)
DE: 6219 Io
DE: 8414 Eruption mechanisms and flow emplacement
DE: 8425 Effusive volcanism
DE: 8485 Remote sensing of volcanoes
SC: Planetary Sciences [P]
MN: 2007 Fall Meeting