M. Ramsey, Department of Geology and Planetary Science, 200 SRCC Building, University of Pittsburgh, Pittsburgh, PA 15260

J. Dehn, Geophysical Institute/Alaska Volcano Observatory, University of Alaska, Fairbanks, AK 99775

The higher spatial and spectral data from the next generation of Earth orbiting satellites are being used for studies of volcanic flows. Remote sensing of active volcanoes commonly provides the only source of monitoring information for remote volcanoes. Beyond monitoring, these data are used to derive fundamental parameters needed for the modeling of volcanic flow processes. One of the most important new spaceborne instruments available to volcanologists is the Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER), which has increased spectral/spatial resolution and a greater dynamic range for high temperature observations. The several-day repeat time for volcanoes at high latitudes has resulted in over 400 frames of data acquired for Kamchatka and the Kurile Islands. With the additional ability to generate digital elevation models (DEMs), ASTER is proving to be a critical instrument for volcanic research. However, in order to capture both large-scale eruptive trends and small-scale volcanic processes ASTER data have been synchronously combined with high temporal, low spatial resolution data from the AVHRR and MODIS instruments, now used by the volcano observatories in this region.

The activity of Bezymianny and Sheveluch volcanoes has been examined in detail during the past two years. Bezymianny, an andesitic to dacitic composite volcano, lies on the southern end of the Kliuchevskoi volcanic group. It has been historically active, producing dome-forming eruptions, block and ash flow deposits and less-common large ash plumes. On average, Bezymianny has two eruptive cycles per year. Sheveluch, a dacitic composite volcano similar in morphology to Bezymianny, also undergoes periods of repeated dome growth. Sheveluch however, does not have eruptions as often as Bezymianny and is less likely to produce large ash emissions. The focus of the activity seems to be on steady dome growth, whereas the rapid dome growth at Bezymianny commonly leads to more violent failure, and larger block and ash flows extending farther from the dome.

At both volcanoes data from the three sensors have been compared, with ASTER revealing much more detail on the dome composition, texture and thermal output. Thermal anomalies show changes in the non-eruptive state of the volcano prior to larger eruptions. The movement of these thermal features may represent the appearance of new fumaroles controlled by the availability of surface water and the creation of new fractures from endogenous dome growth. Prior to large eruptions, these weaker thermal anomalies disappeared almost entirely likely caused by increased pressurization of the dome and a dampening of the fumarolic systems. A detailed comparison of the activity at each volcano is ongoing using the satellite data. The observed variation in precursory activity for volcanoes with similar lava composition reveals important data on dome growth, collapse and hazards at these large stratovolcanoes.

------------------
Submitted: International Union of Geod. and Geophys. (2003)
Date: June 30 - July 11, 2003