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S.3 Geography Notes

Depositional Glacial Features

Moraine dammed lakes are formed by the damming of a valley by terminal moraine- for example Tyndall tarn Hohnel, and hut tarn on mountain Kenya, lac cris on mountain Ruwenzori.  

Moraines refers to all the materials eroded and deposited in low lands by a glacier. There are four types of moraines namely 

a)  Terminal moraines,  

b)  Lateral moraines,  

c)  Ground moraines and  

d)  Medial moraines 

Terminal Moraine: Is an irregular mound or ridge of drift. It is formed by extensive deposition of till at the end/snout of the glacial valley for example Kamusoso valley.  

Lateral Moraine: is a large glacier material formed at the sides of a glacier valley. It was formed when glacier erodes pre - existing depressions/valleys through sapping/plucking/abrasion. In the process glacier debris are transported down slope. The material is later deposited on the sides of the valley to form lateral moraine due to decrease in gradient and melting of the glacier.

Ground moraine: This refers to glacial materials deposited on the floor of the glaciated valley. Medial moraine: it is the glacial materials deposited in the middle if the valley by the tributary glaciers.    

NB: Depositional landforms mainly occur in lowland areas and can be classified as those composed of un- stratified till deposited by ice which include:  

i.  Till plain,  

ii.  Eskers,  

iii.  Drumlin,  

iv.  Eratics,  

v.  Outwash plains,  

vi.  Kettle holes

vii.  Kame terrace 

Drumlins: This is an elongated hills or ridges of oval shape formed when fragments of ground moraine are compresses by ice movement like in Teleki valley. 

Till plain: this is an extensive area of monotonous landscape formed when moving ice transports boulders and clay burying former hills and valleys.

Outwash plains: these are wide gently sloping plains of gravel, sand clay and silt. They are formed when melt waters from a stagnant glacier carry and deposit sorted materials near the mouth of glacier and further down slope. 

Kettle holes: These are circular holes in glaciated drift, blocks of ice detached/left behind during recession. The ice blocks melt leaving enclosed circular depressions. They may be filled by water forming kettle lakes like Mahoma Lake on Mt Rwenzori. 

Kame terrace: This is a narrow flat-topped terrace like ridge of sand and gravel along the valley sides.  

Erratics: These are rock boulders eroded and deposited in lowland areas of completed different rock materials. When the ice melts, it is left stranded in low lands.  

Eskers: These are long winding steep sided ridges lying parallel to the direction of the ice movement. It extends for a long distance and may be about 30m high passing over even low hills.

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