2008 Alaska Park Science Symposium
October 14, 2008
Previously Unrecognized Landforms Produced by Permafrost-Volcano Interactions, Arctic Alaska
James E. Beget1, Rick Wessels2
1Alaska Volcano Observatory, Geophysical Institute, University of Alaska Fairbanks, Fairbanks, AK, 99775-5780, USA, Phone 907-474-5301, Fax 907-474-5163, ffjeb1@uaf.edu
2Alaska Volcano Observatory, U.S. Geological Survey, Anchorage, AK, USA
Volcanic eruptions through permafrost in arctic Alaska have produced unique landforms that have not previously been recognized anywhere on earth. On the Seward Peninsula at ca. 66°N, a series of giant explosion craters known as the Espenberg Maars are as much as 10 km in diameter. These craters were produced by numerous explosions caused by cryo-magmatic interactions. The giant maars formed during eruptions at ca. 18 kyr, 70 kyr, and 150 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 advanced over permafrost only a few thousand years ago. The basaltic lava flow is bounded by unusually steep flow fronts and levees as much as 20 m high, covered with basaltic 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.
At the Ingakslugwat Hills at ca. 61.5°N., unusual composite volcanoes as much as 10 km long and 400 m high are made largely of pyroclastic ejecta. These features are much higher than the regional water table, and yet are capped with numerous intersecting arms of explosion craters of various ages recording repeated cycles of cryo-magmatic explosive volcanism. We call these distinctive landforms Ingakslugwat volcanoes. While the water table is hundreds of meters lower, the water source for continued explosive volcanism was derived from ground ice in permafrost near the ground surface.
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