Which of the following lakes owes its origin mainly to faulting?

Lake Malawi (also known as Lake Nyasa) owes its origin mainly to faulting. It occupies the southern end of the East African Rift System, a massive geological structure formed by tectonic forces pulling the African plate apart. As the Earth's crust was stretched and fractured, blocks of rock dropped down between parallel fault lines, creating a deep, narrow trough called a graben. Lake Malawi fills one of these grabens, reaching depths of over 700 metres.

Other rift valley lakes formed by the same faulting mechanism include Lake Tanganyika, Lake Albert, and Lake Turkana.

The other lakes have different origins:

• Lake Superior was shaped primarily by glacial erosion during the Pleistocene ice ages, when advancing ice sheets scoured and deepened pre-existing river valleys in North America.
• Lake Victoria is not a rift lake. It formed by down-warping (gentle sagging of the Earth's surface) between the eastern and western branches of the rift, creating a broad, shallow basin.
• Lake Chad occupies a shallow depression formed by gentle subsidence in the interior of West-Central Africa. It is an extremely shallow lake, unlike the deep rift lakes.