Explain the influence of denudational processes on the formation of lakes in East Africa

Candidates are to define the Term Lake and denudational processes.

• A lake can be defined as a body of water occupying a hollow or depression on the earth’s surface.
• The term denudatlonal processes refer to the destruction/wearing down of land scape by agents of weathering; erosion and mass-wasting.

However the resultant effect of denudation is deposition of materials in an area.

Where material is eroded from; depressions are created which are later filled with water to form erosional lakes.

Agents responsible for erosion may include glaciations, rivers, and waves.

• Glacially eroded lakes; are made up of hollows created by either valley glaciers or ice sheets.

Cirque/corrie /tarn lakes; These form in arm-chair like depressions in glaciated mountains due to erosional processes-of plucking, abrasion and basal sapping which finally creates hollows that are occupied by ice-melt water to form cirque lakes e.g. Lac – du – Catherine, Speke on Mt. Rwenzori, Teleki, Hidden and hanging tarns on Mt Kenya.

Rock basin lakes: They are formed by the scouring action of an ice–sheet or a valley glacier which results in the formation of shallow hollows known as rock basins which are filled by water to form rock basin Jakes e.g. Lake Michaelson in Gorges valley on Mt. Kenya, Carr Lakes, enchanted lakes in Kenya.

Trough lakes:- It occupies an elongated hollow excavated by ice on the floor of a V – shaped valley to form ribbon lakes because of their shape. E.g. Lake Mahoma in Mubuku trough on Mt Rwenzori.

Eroded material is deposited and this influences formation of depositional lakes.

Ox-bow lakes: Is horse-shore shaped depression formed as a river meanders in a flood plain. Erosion occurs on the concave banks and deposition on the convex banks to produce sharp meander loops separated by a narrow neck of land. The neck is eventually cut through. Edges are sealed off with sediments e.g. include; on R. Tana, Rwizi, Rufigi, Malaba, Nzoia etc.

Delta lakes: These are lakes formed in Delta flood plains when alluvial deposits form levees that stop water in the river and its distributaries e.g. L. Magomeni, L. Mwananyamara in Tanzanian coast.

Lakes produced by marine deposition lagoon lakes): These are formed through long shore drift process forming bars, barrier beaches across bays which cut off part of the lake/ocean e.g. L. Nabugabo on the  western shores of L. Victoria, Kaiso, Tonya lagoons on L. Albert.

Glacial depositional lakes: Marine dammed lakes. Terminal moraines are sometimes deposited across the valley where they form a ridge which dams back the flow of water e.g. Tyndall Tarn on the head or Teleki valley on Mt Kenya, Lac-Cris, Alice on Mt Rwenzori.

Mass-wasting/landslides: These are lakes contained in depressions formed as rock debris are deposited across a river valley, damming it hence forming a lake e.g. L. Bajuku on Mt. Rwenzori, L. Mbaka in Tanzania and Nyabihoko in Ntungamo.

NB: Illustrations and diagrams I Examples are required