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.
History of Central Asia
The economic performance of the region since independence has been mixed. It contains some of the largest reserves of natural resources in the world, but there are important difficulties in transporting them. Since it lies farther from the ocean than anywhere else in the world, and its southern borders lay closed for decades, the main trade routes and pipelines run through Russia. As a result, Russia still exerts more influence over the region than in any other former Soviet republics. Nevertheless, the rising energy importance of the Caspian Sea entails a great involvement in the region by the US. The former Soviet republics of the Caucasus now have their own US Special Envoy and inter-agency working groups. Former US Secretary of Energy Bill Richardson had claimed that "the Caspian region will hopefully save us [the US] from total dependence on Middle East oil".