PRELIMINARY ERS-1 OBSERVATIONS OF ALASKAN AND ALEUTIAN VOLCANOS

We used ERS-1 radar images collected between October 1991 and February 1993 to study volcanic landforms of the Alaska Peninsula and Aleutian Islands. These data were used to map a little-eroded even-textured un it that is a thick low-mobility pyroclastic deposit around Aniakchak c aldera. Also we have identified possible caldera remnants at Black Pea k, and located volcanically related collapse pits and depressions in t he summit glacier of Veniaminof. Observations of Westdahl and Mt. Spur r, both of which erupted during our observation period, demonstrate th at new lava flows and debris flows can be mapped by virtue of their hi gh radar backscatter and contrast with the surrounding terrain. These data demonstrate the utility of frequent orbital radar observations in this area. Regional mapping can be carried out for volcanoes that are difficult to study in the field due to adverse working conditions (e. g., frequent cloud cover, bad weather, long periods of darkness during winter) and remote locations; timely acquisition of images soon after or during an eruption can assist in the monitoring of active volcanoe s. The 23-degrees incidence angle causes strong foreshortening, and th ere is sometimes up to 35 days between repeat observations of certain locations. However, we conclude that the routine collection of SAR dat a from ERS-1 can provide valuable rapid information for assessing volc anic hazards in this region whatever the weather or time of year The s ituation will be improved with the additional use of JERS-1 data and t he launch of the Radarsat spacecraft in 1995.