HR: 11:50h
AN: V12B-07    [Abstracts]
TI: Landforms Produced by Permafrost-Volcano Interactions, Arctic Alaska
AU: * Beget, J
EM: ffjeb1@uaf.edu
AF: Alaska Volcano Observatory, Geophysical Institute, Fairbanks, Ak. 99775 United States
AU: Kargel, J
EM: kargel@hwr.arizona.edu
AF: Dept. Hydrology and Water Resources, University of Arizona POB 210011, Tucson, Az 85721-0011 United States
AU: Wessels, R
EM: rwessels@usgs.gov
AF: Alaska Volcano Observatory, U.S. Geological Survey 4200 University Drive, Anchorage, Ak. 99508 United States
AB: Three different types of distinctive landforms are recognized at sites in Arctic Alaska where volcanic eruptions occurred through permafrost. On the Seward Peninsula at ca. 66° N, a series of giant explosion craters known as the Espenberg Maars are as much as 8 km in diameter. These craters were produced by numerous explosions caused by cryo-magmatic interactions. The giant maars formed during eruptions at 21kyr, 62 ± 10 kyr, and 160 ± 8 kyr., and so are correlative with times of extremely cold climate and thick ground ice during marine isotope stages 2, 4, and 6. At Imuruk Lake at ca. 65° N the Lost Jim lava flow was erupted only a few thousand years ago. The basaltic lava flow advanced over permafrost, and are bounded by unusually steep flow fronts and levees as much as 20 m high, covered with lava flow surfaces sloping as much as 60°. These `super-inflated' flow margins terminate in zones of complex thermokarst collapse features recording melting of ground ice under the lava. We speculate that as the lava flow advanced it melted ground ice and produced steam that quenched the lava and produced extremely steep and inflated flow margins. At the Ingakslugwat Hills at ca. 61.5° N., unusual composite volcanoes as much as 7 km long and 400 m high are made largely of pyroclastic ejecta. These features are significantly higher than the regional water table, and yet are capped with maars and numerous intersecting arms of explosion craters of various. We call these distinctive landforms Ingakslugwat volcanoes. We suggest that since the water table is hundreds of meters lower, the water source for continued explosive volcanism in Ingakslugwat Volcanoes is the melting of ground ice in permafrost. We hypothesize the permafrost table rises in the new ejecta following each successive eruption, resulting in multiple cycles of cryo-magmatic explosive volcanism and the creation of thick complexes of volcaniclastic debris.
DE: 0702 Permafrost (0475)
DE: 1105 Quaternary geochronology
DE: 8408 Volcano/climate interactions (1605, 3309)
DE: 8428 Explosive volcanism
SC: Volcanology, Geochemistry, Petrology [V]
MN: Fall Meeting 2005