Ash Rises Over Shiveluch Volcano
On Sunday morning, February 17, 2008, the skies above Shiveluch Volcano in Russia's Far East were clear and calm. When the Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) on NASA's Terra satellite passed overhead, it caught this view of a column of ash from a recent eruption seemingly frozen in the air over the mountain. The southern slopes of the snow-covered volcano were brown with ash. The top image in this pair shows a close-up view of the ash column, which rises over the volcano to the east (right) of the active caldera. The bottom image shows the entire volcano. In this view, the shadow of the ash column looms over the northern flank of the volcano.
Shiveluch (sometimes spelled Sheveluch) is among the largest and most active of the dozens of volcanoes that sit on the Kamchatka Peninsula in Russia's Far East. The mountain has a rugged and complicated structure. The northern part of the volcano is called â€œOld Shiveluch,â€ a stratovolcano that was active in the late Pleistocene Epoch (the Ice Age). In the Holocene Epoch (the modern geological time period), activity shifted toward a more southern summit, called â€œYoung Shiveluch.â€ The bowl-shaped, shadow-filled feature to the left of the ash column is the crater, or caldera, of Young Shiveluch, where most eruptive activity takes place today.
Shiveluch is the northernmost of the active volcanoes on the Kamchatka Peninsula. The peninsula is along the convergent boundary of two slabs of the Earth's crust: the Okhotsk Plate to the west and the Pacific Plate to the east. Just offshore of the Kamchatka Peninsula is an impossibly deep trench in the ocean floor where the Pacific Plate is diving (subducting) beneath the Okhotsk Plate. This trench, known as the Kuril-Kamchatka Trench reaches depths of more than 10,500 meters (more than 6.5 miles). The Pacific Plate is sliding below the Okhotsk Plate at about 9-10 centimeters per year. This subduction produces frequent earthquakes and explosive volcanic eruptions on the Kamchatka Peninsula.