Story highlights Eastern lobe of what is now known as the South Aral Sea has dried up completely

Recent images from NASA's Earth Observatory show stages of the lake's decline

Disaster began with Soviet-era diversion of lake's tributaries for agriculture

Rising salinity, chemical contamination furthered the calamity

The Aral Sea was once the world's fourth-largest lake. Now much of it is a vast toxic desert straddling the borders of Kazakhstan and Uzbekistan, two former Soviet states in central Asia.

In recently released images, NASA's Earth Observatory shows the extent of the lake's recession over the past 14 years.

The damage reached its peak this year, when the eastern lobe of the South Aral Sea -- which actually was the center of the original lake -- dried up completely.

Until the 1960s, the Aral Sea was fed by two rivers, the Amu Darya and Syr Darya, which brought snowmelt from mountains to the southeast, and local rainfall. But in the 1960s the Soviet Union diverted water from the two rivers into canals to supply agriculture in the region.

With the loss of water, the lake began to recede and its salinity levels began to rise. Fertilizers and chemical runoff contaminated the lake bed. As the lakebed became exposed, winds blew the contaminated soil onto the surrounding croplands, meaning even more water was needed to make the land suitable for agriculture, according to an Earth Observatory release.

The falling water levels changed the local climate, too. Without the lake water to moderate temperatures, winters became colder and summers hotter, the Earth Observatory said.