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.
Caspian Sea
Today, oil and gas platforms abound along the edges of the sea.Countries on the Caspian region, such as Azerbaijan, Kazakhstan and Turkmenistan, illustrate the examples of natural-resource-based economies. A resource-based economy is defined as one where the natural resources, gas and oil, compose more that 10 percent of the particular country's GDP and 40 percent of exports' All the Caspian region economies are highly dependent on the mineral wealth. The world energy markets got influenced by Azerbaijan and Kazakhstan, as they became strategically crucial in this sphere, thus attracting the largest share of FDI (foreign direct investment).