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S.3 Geography Notes

Lakes

LAKES

A Lake is a body of water occupying a hollow/depression on the earth’s surface. Most of the lakes found in Africa are fresh water bodies with few salty lakes. There several Lakes found in Africa and classified according to their mode of formation. These include-

CRUSTAL DOWN WARPED LAKES

These lakes occupy basin- like depressions/Saucer like depressions and were formed by down warping and drainage reversal like Lake Victoria

FAULT LAKES (TECTONIC LAKES)

Rift Valley Lakes/Graben Lakes are found in the rift valley floor. They were formed due to earth movements that culminated into faulting by tensional or compressional forces leading to the formation of the rift valley. The minor Grabens/depressions were formed on the rift valley floor after secondary faulting. The Grabens were later filled with water and accumulated to form rift valley lakes/Graben lakes like Malawi They are elongated, deep, narrow and regular shape.

LAKES DUE TO VULCANIVITY:

These are formed as a result of volcanic activities. These are divided into mountain crater Lakes, Lava dammed Lakes/Lava blocked lake, Explosive/Explosion cater lakes and Caldera Lakes.

LAKES FORMED DUE TO EROSION:

Glacial Erosional lakes formed due to alternating freeze- thaw (frost action). They are known as the cirque Lakes/Tarns.

DEPOSITION LAKES:

These are lakes formed by deposition of weathered material by either water, ice/glaciers, wind or waves. They include River depositional lakes, Wave depositional lakes and glacial deposition lakes.

MAN-MADE LAKES: These are formed due to man’s activities like through the extraction of minerals using open cast method, construction of dams across the rivers; channel development of the agricultural irrigation scheme.

Research work

•   Explain the importance or benefits of lakes to the people of Africa

•   Outline the Problems associated with lakes in Africa

Discussion

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