Stock Photo - Mount Nemrut in Turkey is featured in this image photographed by an Expedition 18 crewmember on the International Space Station. This detailed view centers on the summit caldera of Mount Nemrut (Nemrut Dagi in Turkish), a stratovolcano located in the eastern Anatolia region of Turkey along the shoreline of Lake Van. Winter snow blankets the 2,948 meter elevation summit of the mountain, highlighting the brown caldera rim (a caldera is a large, usually circular or elliptical, collapse feature caused by the rapid emptying of an underlying magma chamber). 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 coldwater caldera lake occupies the western half of the summit. The geologic record at Mt. Nemrut indicates numerous prehistoric explosive eruptions during the Holocene Epoch --which, according to scientists, began approximately 10,000 years ago and extends to the present day -- with eruption of lava last observed during 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 presence of a warm water lake in the caldera suggests that the volcano is merely quiescent at present.