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 thevolcano is merely quiescent at present.
Astronaut photograph ISS018-E-10206
was acquired on December 3, 2008, with a Nikon D2Xs digital camera
fitted with an 800 mm lens, and it is provided by the ISS Crew Earth
Observations experiment and the Image Science & Analysis
Laboratory, Johnson Space Center. The image was taken by the Expedition 18 crew. The image in this article has been cropped and enhanced to improve contrast. Lens artifacts have been removed. The International Space Station Program
supports the laboratory to help astronauts take pictures of Earth that
will be of the greatest value to scientists and the public, and to make
those images freely available on the Internet. Additional images taken
by astronauts and cosmonauts can be viewed at the NASA/JSC Gateway to Astronaut Photography of Earth. Caption William L. Stefanov, NASA-JSC.