I. Five Great Lakes in the World
The total area of lakes on the earth is 2.7 million square kilometers, accounting for 1.8% of the land area, and there are 35 lakes with an area of over 5,000 square kilometers. We can sort the lakes in the world according to their size:
The first place is the Caspian Sea, a saltwater lake with an area of 37 1 000 square kilometers and a storage capacity of 89.6 trillion cubic meters.
The second place is Lake Superior, a freshwater lake with an area of 82,000 square kilometers and the deepest point of 405 meters. The water storage capacity is 6.5438+0.2 million cubic kilometers.
Lake superior
The third place is the freshwater lake Victoria Lake, the largest lake in Africa, with an area of 69,000 square kilometers.
Lake Victoria
The fourth place is the Aral Sea, with an area of about 68,000 square kilometers, but the area is getting smaller and smaller. With the continuous decline of water level, the Aral Sea is divided into two parts: the South Aral Sea and the North Aral Sea, and the South Aral Sea is further divided into two parts: the east and the west. Most of the Aral Sea has dried up and disappeared. The Aral Sea will completely dry up and disappear.
Comparison map of Aral Sea area before and now
The fifth place is Lake Huron, with an area of 59,600 square kilometers, ranking second among the Great Lakes.
great lakes
Second, the formation and general situation of Aral Sea
The Aral Sea, located at the junction of Kazakhstan and Uzbekistan in Central Asia, was originally the fourth largest lake in the world, and its water source mainly depended on the Amu Darya and Syr Darya rivers.
Ancient Mediterranean map
The Aral Sea was formed at the end of Pliocene (7-2.5 million years ago), when the crust sank and surface water accumulated. It is a relic of transgression and is usually considered as a reserved part of the ancient Mediterranean Sea (also known as the Tethys Sea). Since the Pleistocene (2.5 million ~ 1 10,000 years ago), the rivers of Syr Darya and Amu Darya have been injected into the Aral Sea, keeping the water level unchanged.
Fifty years ago, the Aral Sea covered a total area of 66,000 square kilometers, almost equivalent to the land area of Sri Lanka. Abundant water resources have brought great opportunities for the development of local agriculture and fisheries. According to statistics, the annual catch of local fisheries has reached 40,000 tons, there are dozens of small lakes in the tributaries of the delta, and the area of ecologically rich swamps and wetlands has reached 550,000 hectares.
Because the inflow of water (runoff) is less than the evaporation of lake water, the salt content of Aral Sea is much higher than that of freshwater lake. At its peak, the Aral Sea was once the largest saltwater lake in Central Asia and the fourth largest lake in the world, covering an area of nearly 70,000 square kilometers. At its peak, the Aral Sea used to have a well-developed fishery, with more than 40,000 employees along the coast, and the catch accounted for 1/6 of the total catch of the former Soviet Union. The English name of Aral Sea can be roughly translated as "Sea of Islands" because it once had 1500 islands within a hectare.
Aral sea satellite map
There are 1000 islands scattered in the sea. The north shore is rugged, with winding coastline and numerous bays. The northern part of the east coast is the huge Syr Darya Delta, the southern coast is the same as the Amu Darya Delta, and the western coast is the Ustut Plateau. There are marine deposits and continental deposits on the coastline, and the lake bottom is flat and inclined from east to west. Shi Ying, limestone, sand, clay and clay-limestone silt are deposited at the bottom of the lake, which are produced by river rapids scouring the coast and wind and ice erosion.