From NASA and Astronomy Photo of the Day

Our Earth is covered by volcanoes. Volcanoes are breaks in the Earth's cool surface where hot liquid rock from the interior comes out -- sometimes suddenly. In the above image from the ASTER camera aboard NASA's orbiting Terra satellite, snow-capped volcanoes are seen from overhead that compose the picturesque Islands of the Four Mountains in the Aleutian Islands, Alaska, USA. The islands contain restless Mt. Cleveland, an active volcano currently being watched to see if it emits an ash...