Small plume of ash, steam, and gas rises from the summit crater of Redoubt volcano, Alaska, on March 15, 2009. The plume was observed during an observation and gas-measurement flight by scientists of the Alaska Volcano Observatory, probably the result of a steam explosion in the volcano's active shallow hydrothermal system. More explosions could occur with little or no warning and generate ash-rich clouds higher than 20,000 feet above sea level. Photograph by Alaska Volcano Observatory.
