SATELLITE MEASUREMENT OF GLACIERS ON VOLCANOES IN ALASKA: BUILDING AN INVENTORY OF ICE EXTENT AND HAZARDS

In Alaska, at least 30 of the more than 80 volcanic centers of Holocene age are currently mantled by some amount of perennial snow and glacial ice. More than half of these volcanoes have been active historically (~1750 – present). Alaska provides a valuable laboratory in which to examine volcano-ice interactions. Documented historical eruptions and episodes of unrest illustrate a wide range of volcano-ice interaction processes. Recent examples of the influence of volcanic activity on glaciers in Alaska has ranged from the explosive beheading of the Drift River Glacier and lahars during the 1989-1990 Redoubt eruption, to supra- and subglacial lava flows at Veniaminof in 1984 and 1993, to subglacial outbursts of water and debris flows on Spurr in 2004 and Fourpeaked in 2006. Recent geological studies of the pre-historic record of activity at these volcanoes, many still known only in reconnaissance fashion, provide a glimpse into the long-term interaction of ice and volcanic activity in the region.

To better understand the current glaciation of Alaskan volcanoes, its evolution through time, and the relation to volcanic activity, the Alaska Volcano Observatory is building current glacier extent maps for selected volcanoes in the Wrangell Mountains and Aleutian volcanic arc of Alaska using Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER), Landsat Enhanced Thematic Mapper Plus (ETM+), IKONOS, and QuickBird satellite data acquired between 2000 - 2006. We are also analyzing Landsat Thematic Mapper (TM) and Multispectral Scanner (MSS) data from 1972 - 1990 and SAR data, maps and aerial photos for historical comparisons of glacier extent. Preliminary satellite analysis confirms field observations that glaciers on most of the volcanoes have decreased in extent over the last 30-50 years. These new data provide a base for ongoing and future volcano-ice hazard assessments.