Dehn said likely reasons were that a satellite was too far away to look down into Sheveluch s crater and bad weather obscured Korovin. Flights were diverted. Small earthquakes became more frequent in mid 1998 at Shishaldin volcano on Alaska s Unimak Island, and seismic activity accelerated that December. He said routine monitoring of heat from volcanoes was prompted by discovery of excess heat before the 1996 eruption of Alaska s Pavlof volcano. Satellites also detected increased heat emissions before eruptions of Alaska s Okmok in 1997, Russia s Klyuchevskoy in 1994 and Karymsky from 1996 onward, although some other increases in heat were not followed by eruptions.
Scientists use the pictures to track volcanic ash plumes and recognize lava flows and lava domes.
We had to reroute quite a few flights all through the country. Volcanologists hope to use images from advanced infrared instruments on new U.S. and Japanese satellites to monitor volcanoes more often, he said.