Nemrut Dagi, Turkey

When I stumbled across this image, I was a little surprised. Such a youthful-looking caldera in Turkey! Indeed, Nemrut Dagi last erupted only ~360 years ago and lake sediments from the region record multiple eruptions from the volcano over the past thousands of years. Nemrut Dagi is also a compositionally diverse volcano, erupting basalt and rhyolite, on opposite ends of the silica spectrum for magma. This bimodal volcanism is common at many caldera systems like Nemrut Dagi or the less exotic Newberry Caldera in Oregon and is likely related to eruptions where the basaltic input from the mantle is either stopped by rhyolite melt and crystals (producing a rhyolite eruption) or can blast its way to the surface through areas of weakness like faults or fractures in the crust.

Image: From ISS taken December 3, 2003. NASA.