Field mapping of young lava flows at Aleutian volcanoes is logistically difficult, and the utility of optical images from aircraft or satellites
for this purpose is greatly reduced by persistent cloud cover. These factors have hampered earlier estimates of the areas and volumes of three
young lava flows at Westdahl Volcano, including its most recent (1991–1992) flow. We combined information from synthetic aperture radar
(SAR) images with multispectral Landsat-7 data to differentiate the 1991–1992 flow from the 1964 flow and a pre-1964 flow, and to
calculate the flow areas (8.4, 9.2, and 7.3 km2, respectively). By differencing a digital elevation model (DEM) from the 1970–1980s with a
DEM from the Shuttle Radar Topography Mission (SRTM) in February 2000, we estimated the average thickness of the 1991–1992 flow to
be 13 m, which reasonably agrees with field observations (5–10 m). Lava-flow maps produced in this way can be used to facilitate field
mapping and flow-hazards assessment, and to study magma-supply dynamics and thus to anticipate future eruptive activity. Based on the
recurrence interval of recent eruptions and the results of this study, the next eruption at Westdahl may occur before the end of this decade.
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