Morning sunlight illuminates the southeast-facing slopes of the Islands of the Four Mountains, part of the Aleutian Island chain, in this photograph taken from the International Space Station (ISS). Image caption William L. Stefanov, Jacobs at NASA-JSC.
The islands, are actually the upper slopes of volcanoes rising from the sea floor: Carlisle, Cleveland, Herbert, and Tana. Carlisle and Herbert volcanoes are distinct cones and form separate islands. Cleveland volcano and the Tana volcanic complex form the eastern and western ends of Chuginadak Island. A cloud bank obscures the connecting land mass in this image.
Cleveland volcano (elevation 1,730 meters above sea level) is one of the most active in the Aleutian chain, with its most recent activity—eruptions and lava flow emplacement—taking place in May of 2013 (A crew aboard the ISS captured an earlier eruption in 2006.) The northernmost of the islands, Carlisle volcano (peak elevation 1,620 meters), had its last confirmed eruption occurred in 1828, with unconfirmed reports of activity in 1987. Herbert volcano (peak elevation 1280 meters) displays a classic cone structure breached by a two-kilometer wide summit caldera (image lower left), but there are no historical records of volcanic activity. The easternmost peak, Tana (1,170 meters) is a volcanic complex comprised of two east-west trending volcanoes and associated younger cinder cones. Like Herbert volcano, there is no historical record of activity at Tana.
A layer of low cloud and/or fog obscures much of the lower elevations of the islands and the sea surface, but the clouds also indicate the general airflow pattern around and through the islands. Directly to the south-southeast of Cleveland volcano, a Von Karman vortex street is visible. Shadows cast by the morning sun extend from the peaks towards the northwest. The peaks of all the Four Islands have snow cover. This is distinct from the clouds due to both higher brightness (white versus gray) and the specific place on the landscape.