Space shuttle astronauts witnessed this eruption of the large stratovolcano Klyuchevskaya on October 1, 1994 (U.S. time). This near-vertical view shows the main eruption plume, which consisted of hot gas and volcanic ash. The hot rising plume stalled at the tropopause, a temperature inversion in the upper atmosphere. Strong eastward winds at an altitude of 8–10 kilometers drove the plume out to sea, forming a long narrow trail that ultimately dispersed into the atmosphere. This is in contrast to eruption plumes on Jupiter's moon Io, which, in the absence of an atmosphere, follow ballistic trajectories and form circular umbrella-shaped eruption plumes hundreds of kilometers across.
Klyuchevskaya is part of the Klichii group of eight stratovolcanos. This group lies in the heart of the rugged Kamchatka Peninsula, one of the most volcanically active regions on Earth. These volcanos are part of the “Ring of Fire,” a belt of volcanos and earthquakes that surrounds the Pacific Ocean (see slide #10). This geologic activity is related to the subduction of oceanic crust into the mantle and is part of the global tectonic system called plate tectonics.