The Caspian Sea is the largest lake on Earth. It is four times larger than Lake Superior, the second largest lake. However, the Caspian Sea was once much larger, and today, its area continues to decline.The Caspian Sea is surrounded by Russia, Azerbaijan, Iran, Turkmenistan and Kazakhstan.
An inland sea once covered the region around the Caspian Sea. Its exact magnitude is unknown, but it reached at least as far as the Aral Sea in the east, and the Azov Sea in the west.
In more recent times, the Caspian Sea filled an enormous depression between the borders of Russia, Turkmenistan and Iran. This region, the largest exposed depression on earth, has an area of more than 520,000 square kilometers. The Caspian Sea now fills only 371,000 km² of that depression. The coasts of this sea went 400 km into what is now the mainland.
In more recent years, the level of the Caspian Sea has dropped by about 20 metres. Its surface is 28 metres below sea level.
The salinity level of the Caspian Sea is one third that of the ocean.
.
