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Lakes are classified depending on how they formed and on the
quality of the water (freshwater or saltwater). Only in the
saltiest lakes there is no life.
1.Tectonic lakes. The movements of the Earth's crust formed
the largest lake, the Caspian Sea, and the deepest, Lake Baikal.
Caspian Sea is located in a depression between the Caucasus
Mountains and Central Asia and its surface is still varying,
millions of years after its emergence.
2.Volcanic lakes. The most common form is the one filling the
caldera of a shut-off volcano. Some volcanic lakes form when
the lava seeps on the slopes, solidifying due to the cold waters.
3.Glacial lakes appear following the melting of the glaciers.
They are more common in the Northern Hemisphere: Most
lakes in the UK, Finland (about 60,000 !) or Alps formed this
way.
4.Karstic lakes form in calcareous regions and can be subterranean
as well. Water dissolves the limestone creating huge caves
harboring rivers and lakes.
5.Salt lakes. Most lakes contain freshwater and are continuously
supplied with water from the exterior. If the supply of freshwater is
limited, minerals from the bottom of the lakes can enter into the
water's composition and concentrate, turning the lake salty. The
Great Salt Lake from Utah formed this way.
The Caspian Sea and the Aral Sea are salty too. INVESTIGATE
WHERE ARE THEY
6.Artificial lakes. The most common are reservoirs, like Lake Nasser,
formed through the interception of the Nile, and Lake Mead (US),
formed through the interception of the Colorado River. They
generate hydroelectric power. Many artificial lakes serve as water
reservoirs, supplying water for industries and home usage.