This detailed astronaut photograph centers on the summit caldera of Mount Nemrut (Nemrut Dagi in Turkish), a stratovolcano in the eastern Anatolia region of Turkey, along the shoreline of Lake Van. Winter snow blankets the 2,948-meter (9,672-foot) summit of the mountain, highlighting the brown caldera rim. (A caldera is a large crater, usually circular or elliptical, formed when the underlying magma chamber empties rapidly.)
The snow also highlights the irregular shape and wrinkled surfaces of several lava flows present in the eastern portion of the caldera. Lava flows associated with Mt. Nemrut range in composition from thin, fluid basalt to thick, glassy obsidian. A cold-water caldera lake occupies the western half of the summit.
The geologic record at Mt. Nemrut indicates numerous prehistoric explosive eruptions during the Holocene Epoch (from about 10,000 years ago through the present); the last observed eruption of lava was in 1441. The last well-documented explosive eruption occurred during 1650. Volcanism at Mt. Nemrut is the result of tectonic activity associated with the collision of the Arabian and Eurasian Plates; this collision is ongoing, and the volcano is merely quiescent at present.