The Largest Lake

The Caspian Sea (Russian: Каспийское море, Persian: دریای مازندران یا دریای خزرDaryâ-ye Mâzandarân , Azerbaijani: Xezer Denizi) is the largest enclosed body of water on Earth by area, variously classed as the world's largest lake or a full-fledged sea. The sea has a surface area of 371,000 square kilometres
(143,244 sq mi) and a volume of 78,200 cubic kilometres (18,761 cu mi). It is in an endorheic basin (it has no outflows) and is bounded by northern Iran, southern Russia, western Kazakhstan and Turkmenistan, and eastern Azerbaijan. It has a maximum depth of about 1,025 metres (3,363 ft).

The ancient inhabitants of its littoral perceived the Caspian as an ocean, probably because of its saltiness and seeming boundlessness. It has a salinity of approximately 1.2%, about a third the salinity of most seawater. Caspian is called Qazvin (قزوين or بحر قزوين) on ancient maps. In Iran, it is sometimes referred to as Daryâ-ye Mâzandarân (دریای مازندران).

Geological history

Like the Black Sea, the Caspian Sea is a remnant of the ancient Paratethys Sea. The Caspian Sea became landlocked about 5.5 million years ago due to tectonic uplift and a fall in sea level. During warm and dry climatic periods, the landlocked sea has all but dried up, depositing evaporitic sediments like halite that have become covered by wind-blown deposits and were sealed off as an evaporite sink when cool, wet climates refilled the basin. Due to the current inflow of fresh water, the Caspian Sea is a fresh-water lake in its northern portions. It is more saline on the Iranian shore, where the catchment basin contributes little flow. Currently, the mean salinity of the Caspian is one third that of the Earth's oceans. The Garabogazköl embayment, which dried up when water flow from the main body of the Caspian was blocked in the 1980s but has since been restored, routinely exceeds oceanic salinity by a factor of 10.

Geography

The Caspian Sea is the largest inland body of water in the world and accounts for 40 to 44 percent of the total lacustrine waters of the world. The coastlines of the Caspian are shared by Azerbaijan, Iran, Kazakhstan, Russia, and Turkmenistan. The Caspian is divided into three distinct physical regions: the Northern, Middle, and Southern Caspian. The North-Middle boundary is the Mangyshlak threshold, which runs through Chechen Island and Cape Tiub-Karagan. The Middle-South boundary is the Apsheron threshold, a sill of tectonic origin that runs through Zhiloi Island and Cape Kuuli. The Garabogazköl bay is the saline eastern inlet of the Caspian, which is part of Turkmenistan and at times has been a lake in its own right due to the isthmus which cuts it off from the Caspian.

Divisions between the three regions are dramatic. The Northern Caspian only includes the Caspian shelf, and is characterized as very shallow; it accounts for less than one percent of the total water volume with an average depth of only 5–6 metres (16–20 ft). The sea noticeably drops off towards the Middle Caspian, where the average depth is 190 metres (623 ft). The Southern Caspian is the deepest, with a depth that reaches over 1,000 metres (3,281 ft). The Middle and Southern Caspian account for 33 percent and 66 percent of the total water volume, respectively. The northern portion of the Caspian Sea typically freezes in the winter, and in the coldest winters, ice will form in the south.

Over 130 rivers provide inflow to the Caspian, with the Volga River being the largest. The Caspian also has several small islands; they are primarily located in the North and have a collective land area of roughly 2,000 km2 (770 sq mi). Adjacent to the North Caspian is the Caspian Depression, a low-lying region 27 metres (89 ft) below sea level. The Central Asian steppes stretch across the northeast coast, while the Caucasus mountains hug the Western shore. The biomes to both the north and east are characterized by cold, continental deserts. Conversely, the climate to the southwest and south are generally warm with uneven elevation due to a mix of highlands and mountain ranges; the drastic changes in climate alongside the Caspian have led to a great deal of biodiversity in the region.

The Largest Freshwater Lake

Lake Superior (French: Lac Supérieur) is the largest of the five Great Lakes of North America. It is bounded to the north by the Canadian province of Ontario and the U.S. state of Minnesota, and to the south by the U.S. states of Wisconsin and Michigan. It is the largest freshwater lake in the world by surface area and is the world's third-largest freshwater lake by volume.

Lake Superior is the largest freshwater lake in the world by surface area, and empties into Lake Huron via the St. Marys River and the Soo Locks. Lake Baikal in Russia is larger by volume, as is Lake Tanganyika. The Caspian Sea, while larger than Lake Superior in both surface area and volume, is brackish; though presently isolated, historically the Caspian has been repeatedly connected to and isolated from the Mediterranean via the Black Sea.

Lake Superior has a surface area of 31,820 square miles (82,413 km2) — which is larger than South Carolina. It has a maximum length of 350 miles (563 km) and maximum breadth of 160 miles (257 km). Its average depth is 482 feet (147 m) with a maximum depth of 1,332 feet (406 m). Lake Superior contains 2,900 cubic miles (12,100 km³) of water. There is enough water in Lake Superior to cover the entire land mass of North and South America with 1 foot (30 cm) of water. The shoreline of the lake stretches 2,726 miles (4,387 km) (including islands).