Covering an area of roughly 371,000 square kilometers (143,200 square miles), the Caspian Sea is the world’s largest salt lake. The water appears green in its shallow northern part, where it has an average depth of just 5 to 6 meters (16 to 20 feet). The southern part of the Caspian Sea is much deeper and appears dark blue.
A hazy plume drifted over the northern end of the Caspian Sea in early April 2008. The translucent plume swirling over the water contrasts with the nearby opaque white clouds. The plume might result partly from smoke from springtime agricultural fires in farmland north of the sea.