Lakes are found mostly in high latitudes, in mountainous regions, along rivers and in lowland areas. They vary in size and shape as over centuries, the Earth’s crust has undergone many changes.
The crust has split in many places causing folds and depressions of immense size. These have resulted in very deep and vast lakes like, the Caspian and the Dead seas.
Lakes have also been formed by blocking of water courses in mountains, etc.
The nature of the terrain has determined the various shapes of lakes all over the world.
Below Lake info from Wikipedia (Read More):-
A lake (from Latin lacus) is a terrain feature (or physical feature), a body of liquid on the surface of a world that is localized to the bottom of basin (another type of landform or terrain feature; that is, it is not global) and moves slowly if it moves at all. On Earth, a body of water is considered a lake when it is inland, not part of the ocean, is larger and deeper than a pond, and is fed by a river.[2][3] The only world other than Earth known to harbor lakes is Titan, Saturn's largest moon, which has lakes of ethane, most likely mixed with methane. It is not known if Titan's lakes are fed by rivers, though Titan's surface is carved by numerous river beds.
http://en.wikipedia.org/wiki/Lake
