Volcanic craters dot the 5,400 square mile (14,000-square kilometer) lava field of Harrat Khaybar in Saudi Arabia, as seen from the International Space Station.

The volcanic field formed through eruptions along a 62-mile (100 kilometer) vent system during the past 5 million years, with the most recent recorded eruption taking place between 600 – 700 A.D. the Jabal Abyad crater (bottom) formed from viscous, silica-rich lava. By contrast, the Jabal Bayda crater (center right) is a "tuff cone" that formed from the build-up of lava eruptions in the presence of water. The white deposits inside Jabal Bayda represent sand and silt that can build up in such shallow, protected depressions.

Such tuff cones and other volcanic features indicating water suggest that the local climate was much wetter during some periods of volcanic activity. However, today the region is hyperarid with little to no yearly rainfall.

• Satellites at SPACE.com
• Observing Earth: Amazing Views of Earth from Space, Part Two
• About Planet Earth

— NASA and SPACE.com Staff

Credit: NASA