English: On August 31, 2020, the Moderate Resolution Imaging Spectroradiometer (MODIS) on board NASA’s Terra satellite acquired a true-color image of swirling colors in the north-eastern Caspian Sea.

The Caspian Sea, measured by surface area, is the Earth’s largest inland water body. It spans about 143,200 square miles (371,000 square kilometers) and borders five countries. The saline lake plunges to about 3,300 feet (1,000 meters) in the south, but the northern waters are as shallow as 16-20 feet (5-6 meters).

Several rivers empty into the Caspian Sea, including Europe’s longest river, the Volga. At the border of southern Russia and western Kazakhstan the river widens into more than 500 channels, creating a remarkably broad delta where silt-laden fresh water pours into the Caspian Sea. These waters also carry nutrients from large quantities of agricultural and industrial runoff, spurring growth of algae and phytoplankton blooms. In this image, the Volga River Delta can be seen along the northeast coast of the Caspian Sea. Tan colors mark sediment which has been carried into the waters and suspended by currents stirring up the very shallow bottom. Most of the green color likely comes from algae or phytoplankton floating in the waters.