How Lakes Are Made: Volcanoes, Rifts and Ice

Crater Lake sits in the caldera of the collapsed volcano Mount Mazama in Oregon. With no inlet or outlet streams and only rain and snowmelt to fill it, it is the deepest lake in the United States and one of the clearest and bluest in the world.

Lake Taupo fills the caldera of a supervolcano on New Zealand's North Island. It is the largest lake in the country, with a surface area of 616 square kilometres, and its basin is a reminder that a volcanic bowl can be broad as well as deep.

Lake Toba on Sumatra is the largest volcanic lake in the world, occupying the caldera of a supervolcano. The island of Samosir rises from the lake itself, formed by later resurgent volcanic activity, so the lake's shape keeps recording the eruption.

Lake Assal in Djibouti is a hypersaline crater lake and the lowest point in Africa, more than 150 metres below sea level. Its extreme salinity has long supported a small salt-extraction trade, showing a volcanic basin that loses water faster than it gains it.

Lake Albert lies on the border of Uganda and the Democratic Republic of the Congo in the western branch of the Great Rift Valley. Its outflow, the Albert Nile, is one of the sources of the Nile system, and its surface area is about 5,270 square kilometres.

Lake Kivu, on the border of Rwanda and the Democratic Republic of the Congo, is unusual among large lakes for holding vast quantities of dissolved methane and carbon dioxide in its depths. That buildup is a rare natural hazard and also a source of extractable gas.

Lake Nakuru is a shallow alkaline lake in Kenya's Rift Valley, famous for flocks of flamingos drawn by its algae. Its surface area grew from 40 to 68 square kilometres between 2010 and 2020, which shows how a shallow rift lake changes with its water level.

Lake Khovsgol in far northern Mongolia is the country's largest lake by volume and is sometimes called the younger sister of Lake Baikal for its clarity and geological origin. It holds roughly one percent of the world's fresh water despite a modest surface area.

Lake Ohrid, shared by North Macedonia and Albania, is one of Europe's oldest and deepest lakes. Its waters have been evolving endemic aquatic life for more than a million years, and the city of Ohrid on its shore is a UNESCO World Heritage site.

Lake Argentino is the largest lake in Argentina, with a surface area of 1,415 square kilometres. Meltwater from the Southern Patagonian Ice Field, including the Perito Moreno Glacier that calves into it, gives the water a milky turquoise colour from finely ground rock flour.