This south-looking view shows the dark Volga River (bottom) and its delta where they meet the Caspian Sea. This delta occupies approximately 200 kilometers of the coastline and serves as a major bird-life center in the region. Recent rising water levels (still poorly understood) have caused the seaward installations such as diked barge canals to be inundated and damaged. This development is troublesome because the Volga River is one of the most important shipping waterways in Russia. Fishing is important in the Volga River and Caspian Sea, and the latter provides 25% of the world’s supply of caviar-producing sturgeons.
The floodplain of the Volga is used intensively for agriculture. Numerous small, light-colored patches around the delta are small settlements occupied by the sheep and cattle herders of this flat, semiarid steppe country. Mixed in with these are numerous oil drilling sites. Petroleum deposits in this type of terrestrial setting are fairly common, as the high concentration of organic matter on deltas becomes buried by successive layers of sediment. Eventually the organic-rich muds reach a depth at which they begin to heat up and break down into petroleum products. The presence of oil suggests that the Volga River has fed the Caspian Sea for a significant amount of geologic time.
April–May 1991, image STS-39-151-07.