Caspian Sea
The Caspian has characteristics common to both seas and lakes. It is often listed as the world's largest lake, although it is not a freshwater lake. It contains about 3.5 times more water, by volume, than all five of North America's Great Lakes combined. The Caspian was once part of the Tethys Ocean, but became landlocked about 5.5 million years ago due to plate tectonics. The Volga River (about 80% of the inflow) and the Ural River discharge into the Caspian Sea, but it has no natural outflow other than by evaporation. Thus the Caspian ecosystem is a closed basin, with its own sea level history that is independent of the eustatic level of the world's oceans.
Garabogazköl
The salinity of the bay is about 35%, compared to the Caspian Sea's 1.2%, and 3–4% for the bulk of the world's oceans. Because of the exceptionally high salinity, comparable to the Dead Sea, it has practically no marine vegetation. Large evaporite, mostly salt deposits accumulated at the south shore were harvested by the local population since the 1920s, but in the 1930s manual collection stopped and the industry shifted northwest to its present center near Garabogaz. From the 1950s on, ground water was pumped from levels lower than the bay itself, yielding more valuable types of salts. In 1963 construction began at Garabogaz on a modern plant for increased production of salines, all the year round and independently of natural evaporation. This plant was completed in 1973.
In March 1980, the barrier to the Caspian was blocked, due to concerns evaporation was accelerating a fall in Caspian Sea level, reducing water levels. The resulting "salt bowl" caused widespread problems of blowing salt, reportedly poisoning the soil and causing health problems for hundreds of kilometers downwind to the east. In 1984 the lake was completely dry. In June 1992, when Caspian Sea levels were rising again, the barrier was breached, allowing Caspian water to again refill Garabogazköl. The remnants of the breached dam can be seen in the satellite photo of the inlet, near the Caspian Sea entrance.