Lakes are classified by what made the hollow that holds their water, and the main types are tectonic (basins opened by faulting, such as Lake Baikal, the world’s deepest at 1,642 m), volcanic (craters and calderas, such as Oregon’s Crater Lake), glacial (basins scoured or dammed by ice, such as Lake Superior), landslide-dammed (such as Sarez Lake in Tajikistan), fluvial (oxbow lakes cut off from meandering rivers), solution (sinkholes in limestone), coastal (lagoons behind sandbars) and artificial (reservoirs behind dams, such as Ghana’s Lake Volta). A separate label, endorheic, describes any lake with no outlet to the sea, which usually makes it salty, like the Dead Sea. The six lakes below each show one of these origins at work.
The standard scheme comes from the English-born Yale ecologist G. Evelyn Hutchinson, whose 1957 A Treatise on Limnology sorted lakes into 11 major types and 76 subtypes by origin. Most lakes are small: one widely cited estimate puts Earth’s total at 304 million lakes and ponds, 91% of them a hectare or less. Yet almost all lake water sits in fewer than 100 large lakes, and the two deepest of them, Baikal and Tanganyika, fill tectonic rifts.
Lake Baikal: a rift lake 25–30 million years old
Lake Baikal in southern Siberia fills part of the Baikal Rift Zone, where the Earth’s crust is being pulled apart at about 4 mm a year. That stretching has produced the deepest lake on Earth: the water reaches 1,642 m, its floor lies 1,186.5 m below sea level, and beneath that are about 7 km of sediment, putting the true rift floor 8 to 11 km below the surface. That makes it the deepest continental rift on Earth.
Baikal is also estimated to be 25 to 30 million years old, making it the oldest lake known. It is 636 km long and covers 31,722 km², but its depth is what matters: it holds about 23,615 km³ of water, some 22–23% of the world’s fresh surface water and more than all five North American Great Lakes combined. About 330 rivers flow in, led by the Selenga, and only one, the Angara, flows out. Because no ice sheet ever scoured its bed, its sediments are an unbroken archive: cores drilled by Russian, American and Japanese teams in the 1990s record climate change over the past 6.7 million years. UNESCO listed the lake as a World Heritage Site in 1996.
Rift lakes tend to be long, narrow and very deep, and Africa has the next-best example. Lake Tanganyika, in the Albertine Rift on the western branch of the East African Rift, reaches 1,471 m and is the second-deepest and second-largest freshwater lake by volume, shared by Tanzania, the Democratic Republic of the Congo, Burundi and Zambia.
Crater Lake, Oregon: a volcano that collapsed 7,700 years ago
Volcanic lakes form in craters, maars and calderas. The difference matters: a crater is a vent, while a caldera is the much larger hole left when a volcano empties its magma chamber and the summit falls in. Crater Lake in south-central Oregon is a caldera lake. About 7,700 years ago the volcano Mount Mazama erupted and collapsed, and over an estimated 720 years rain and snow filled the caldera to a depth of 594 m. That makes it the deepest lake in the United States and the second deepest in North America, after Great Slave Lake in Canada.
No rivers flow in or out. The lake stays level because precipitation balances evaporation and seepage, and its whole volume is replaced roughly every 150 years. The lake is known for its deep blue colour and clarity: Secchi disk readings have long measured about 37 m, though a 2025 reading of 24 m suggests the water is getting cloudier. Eruptions on the caldera floor between about 7,700 and 7,200 years ago built Wizard Island, a cinder cone of about 128 hectares near the western shore. Our guide to Crater Lake’s geography covers the national park around it.
Lake Superior: an ice-scoured basin on an ancient rift
Glacial lakes are the most numerous lakes in the world, formed where ice gouged hollows in bedrock or left moraines and drift that blocked valleys. Lake Superior shows how glaciation can reuse an older structure. Its basin follows the Midcontinent Rift, a Mesoproterozoic tear in North America that failed to split the continent and left basalt that now forms Isle Royale and Michipicoten Island.
The lake itself is young. During the Wisconsin glaciation the region lay under ice about 2 km thick, which deepened and shaped the old rift lowland. As the ice retreated around 10,000 years ago, meltwater pooled in the basin as Lake Minong, the forerunner of today’s lake, and the land, freed of the ice’s weight, rebounded until an outlet formed at Sault Ste. Marie, today’s St. Marys River. The result is the largest freshwater lake in the world by surface area, about 82,000 km² and up to 563 km long and 257 km wide, with an average depth of 147 m, a maximum depth of 406 m and about 12,100 km³ of water. The Ojibwe name, gichi-gami, means “great sea”.
The Dead Sea: an endorheic lake 440 metres below sea level
A lake with no outlet loses water only by evaporation, so the salts that rivers bring in stay behind. The Dead Sea lies in the endorheic basin of the Jordan Rift Valley, bordered by Jordan to the east, the West Bank to the west and Israel to the southwest, with the Jordan River as its main source. Its surface stood 439.78 m below sea level in 2025, making its shores the lowest land on Earth. At 304 m deep it is the deepest hypersaline lake in the world, and in 2011 its salinity was measured at 34.2%, about 9.6 times saltier than the ocean, with water so dense that swimmers float.
The Dead Sea also shows how fast an endorheic lake responds to human water use. With much of the Jordan’s flow diverted upstream, its surface area has shrunk from 1,050 km² in 1930 to about 605 km² today. Proposals to top it up, including the Red Sea–Dead Sea Water Conveyance, have so far been dropped.
Sarez Lake: dammed by an earthquake in February 1911
Some lakes appear in a single night. In February 1911 an earthquake in the Pamir Mountains of what is now Tajikistan shook loose roughly 2 km³ of rock, which buried the village of Usoi and blocked the Murghab River. Deaths were estimated at 302, and the valley was so isolated, its mountain tracks so thoroughly destroyed, that news took six weeks to reach the Russian posts at Murghab and Khorog. The natural dam, named the Usoi Dam after the lost village, rises about 567 m from the old valley floor, making it the tallest dam in the world, natural or man-made. Behind it Sarez Lake filled to about 16 km³ of water, with its surface at roughly 3,263 m above sea level.
Landslide lakes are often short-lived because water spilling over the top erodes the dam. Sarez survives because water seeps out through the base of the rubble at about 45 cubic metres per second, roughly matching inflow, so the level rises only about 20 cm a year. Geologists still worry about it. The dam came through a magnitude 7.2 earthquake on 7 December 2015 with no visible damage, but assessments differ: a 1997 conference in Dushanbe judged it unstable in a strong earthquake, while a 2004 World Bank study held it stable, and a partly detached rock mass of about 3 km³ above the lake could one day fall in and send a flood down the narrow valley below.
Lake Volta: a reservoir that displaced 80,000 people
Artificial lakes are now a type in their own right, and the largest by surface area is Lake Volta in Ghana. It formed behind the Akosombo Dam, built between 1961 and 1965 on the Volta River to power an aluminium smelter, and it filled between 1962 and 1966. The lake covers 8,502 km², about 3.6% of Ghana, and stretches some 520 km from the dam north to near Yapei, drowning the point where the White Volta and Black Volta once met. By volume, at about 148 km³, it ranks third among reservoirs, behind Lake Kariba’s 185 km³.
Reservoirs differ from natural lakes in their costs as well as their origin. Filling Lake Volta forced the relocation of about 80,000 people, then around 1% of Ghana’s population, from roughly 700 villages into 52 resettlement villages, and resettlement proved complex: in some cases traditional farming practices disappeared and poverty increased. Fertiliser use on the poorer soils around the lake led to eutrophication and the spread of an invasive weed, Ceratophyllum, which harbours the black-flies, mosquitoes and snails that spread bilharzia, river blindness and malaria. The dam’s output, originally 912 MW, was raised to 1,020 MW in 2006, and it supplies the majority of the electricity used in Togo and Benin as well as Ghana.
Smaller lake types fill in the rest of Hutchinson’s list: sinkhole lakes in dissolving limestone, lagoons behind coastal sandbars, and the oxbow lakes that form when a meander is cut off, which our guide to the types of rivers explains from the river’s side. For the record-holders in this article ranked side by side, see our list of the deepest lakes in the world.