HR: 1340h
AN: P23B-0195    [Abstracts]
TI: Martian and Ionian Analogs of Permafrost-Volcano Interactions in Alaskan Permafrost
AU: * Kargel, J S
EM: kargel@hwr.arizona.edu
AF: Department of Hydrology & Water Resources, Harshbarger Building University of Arizona, Tucson, AZ 85742 United States
AU: Beget, J E
EM: ffjeb1@uaf.edu
AF: Department of Geology & Geophysics, University of Alaska at Fairbanks, Fairbanks, AK 99775 United States
AU: Skinner, J A
EM: jskinner@usgs.gov
AF: Astrogeology Team, U.S. Geological Survey 2255 N. Gemini Dr., Flagstaff, AZ 86001 United States
AU: Wessels, R
EM: rwessels@usgs.gov
AF: Alaska Volcano Observatory, U.S. Geological Survey, Anchorage, AK 99508 United States
AB: Volcanic landforms in Alaskan lowland permafrost exhibit several unique morphological attributes, as described in a companion AGU abstract (Beget et al.). These features include (1) giant maar sizes (in Bering Land Bridge National Preserve) an order of magnitude larger than common in non-permafrost terrains, (2) composite volcanic forms produced by repeated maar-forming explosions (the novel Ingakslugwat-type volcano in Yukon Delta), and (3) super-inflated lava flows with marginal thermokarst pits (Lost Jim flow, Imuruk Lake Volcanic Field, Bering Land Bridge area). We have identified on Mars, in areas not indicating glaciation, several landforms and on Io an active volcanic process that might be analogs of these in Alaska. On Mars, within and near Elysium (Galaxias Fossae and Hrad Vallis region) multiple crater-like depressions occur with other volcanic features. Their characteristics suggest that the depressions are maars. The composite structures suggest similarities to Ingakslugwat volcanoes. Possible analogs of giant oversize maars also have been identified on Mars. In addition to surface gravitational differences between Earth and Mars, it seems likely that volatile composition is a key aspect controlling the explosivity and sizes of maars on both planets. In Alaska, we suspect that volcanic interactions with methane clathrate hydrate-rich permafrost tends to yield larger maar sizes than with ice-rich permafrost or ground water. This working hypothesis fits well with observations that the giant maars formed during the climatically coldest periods (Beget et al., 2005, this conference). During those periods, permafrost was thick, strong, and unpunctured by lakes and rivers, and so it could have trapped clathrate-forming gases. During interglacials, thinner permafrost and the widespread occurrence of thaw lakes and surface streams may cause the permafrost to be ineffective in confining ascending gases, and so clathrates were absent or not abundant, and volcanic interactions involved mainly weak explosions with H2O. Mars is today and through its history has primarily been in a condition similar to (or colder than) severe full-glacial permafrost conditions on Earth, and so any mantle or crustal sources of methane or CO2 could produce clathrate phases; hence, on Mars, we predict (1) an abudnance of clathrate hydrates and (2) where volcanism occurs in clathrate-rich permafrost, large maar sizes are common. On Io, the Galileo orbiter obtained images of an actively advancing, hot lava flow that was over-riding a volatile-rich substrate, with consequences for gas venting along the flow margins. The geyser-like venting phenomenon is inferred from the occurrence of fresh bright streaks that appeared to have been erupted from points along the margins of the lava flow. In this case, the volatile material is thought to be mainly sulfur dioxide, which exists as solid ice in the shallow crust and as a liquid at greater depths, much like the relationship of H2O phases in terrestrial permafrost. Flow-margin thermokarst in the Alaskan flow may have involved similar volcano-volatile interaction.
DE: 0702 Permafrost (0475)
DE: 0714 Clathrate
DE: 5422 Ices
DE: 5480 Volcanism (6063, 8148, 8450)
DE: 6225 Mars
SC: Planetary Sciences [P]
MN: Fall Meeting 2005