GLACIAL EROSION FEATURES OR GLACIAL UPLAND FEATURES

 CIRQUES/CORRIE/TARNS/CWMS.

These are semi-circular steep sided rock basins which have been cut into the sides of a glaciated mountain.  It is formed when water enters the rocks and freezes breaking them down. The joints become enlarged. Abrasion drags the debris over the rock floor deepening the depression, back wall cutting or recession also enlarged the depression as well as steepening the sides. Plucking also steepens the cirque, when filled with water, it forms a tarn (lake) such as teleki and mawenzi on mountain Kenya and Kilimanjaro respectively. Others are Lac du Noah, Lac du Catherin and Lac du vent on mountain Rwenzori.

GLACIAL EROSION FEATURES OR GLACIAL UPLAND FEATURES


Pyramidal peak /horn

this is a jagged peak formed by the steepening of the back walls of several cirques which lie on the sides of a glaciated mountain. Two or more cirques cut back into the original mountain sides leaving an isolated peak called a pyramidal peak.  These peaks become shaped by frost action. Examples include kibo, mawenzi on mountain Kilimanjaro and margarita peak on mountain Rwenzori.

Arête.

This is a sharp knife like feature or narrow ridge in between two or more cirques on the mountain sides. It's formed when two or more cirques erode backwards (back to back) in the process of head Wall recession. The wall between the cirques collapses by sapping. Best examples can be seen on my Rwenzori from Mount Backer up-to bujuku Valley and point John and midget peaks on mountain Kenya.

U-shaped valleys or glacial troughs.

These are broad flat bottomed steep sided valleys with an open u shape in the cross profile. These were usually former river valleys which are filled by glaciers. Through the process of abrasion, plucking and sapping, the valley floor and sides were worn away hence deepening and widening the valley.  So the valley is changed from a V-shape to an open U-shape hence its name. within this widened Valley or trough are a number of other landforms for example rock steps, moraine materials etc.

Examples of u shaped valleys include Mubuku valley, bubusu Valley and komusonso valleys on mountain Rwenzori, hobley and teleki valleys on mountain Kenya and the karanga through on mountain Kilimanjaro.

Hanging valley

These are small narrow short and V-shaped valleys found in highland areas through which river glaciers from the cirque pass. Hanging valleys are tributary valleys of the U-shaped valleys joining the U-shaped valleys at vertical slopes forming water falls at that point. For example, nithi river is joined by the little nithi from a hanging valley on mountain Kenya.

Truncated spurs

Interlocking spurs of a former river valley are cut off by lateral erosion resulting from accumulated glaciers in the valley forming a U-shaped valley with Truncated spurs instead of interlocking spurs for example around Mubuku and bujuku Valleys on mountain Rwenzori.

Rock basins

These are depressions that are filled with water to form lakes along the glaciated Valley. They are formed by glaciers when they scoop out rock protrusions along its paths to form hollows which are filled by water to form rock basins.

similarly, the path of the glacier may have rocks of different types and resistance to weathering and erosion. Where a band of soft rocks Alternate with bands of hard rocks, the soft rocks will be worn out to form a depression which is filled by water to form a basin lake. Best examples include lac Michaelson on mountain Kenya, Lac nour and Lac vert in the kamusoso valley on mountain Rwenzori.

Rock steps.

These are hard rock projections in the glacial valley forms as a result of differential erosion due to difference in rock resistance and variation in glacier thickness. The increased ice in the main valley makes it possible to cut deep in the valley creating step like features known as rock steps for example at Vivian falls on mountain Kenya

Crag and tail.

This is an elongated rock mass with a steep slope on the upstream which protects the softer lee ward rock from being eroded or worn out by the glacier. Its formed when advancing ice meets a resistant rock protecting a weaker rock downstream from erosion leading to the formation of an elongated tail on the side of the weaker rocks while the resistant rock mass forms a crag with a steep slope.

Rock montane.

These are rock masses glacially molded with a smooth gently sloping up stream, smoothen by abrasion of ice. The downstream is steep and rough due to plucking of ice. Examples can be found at the mobuku valley along the slopes of mountain Rwenzori and along the George valley on mountain Kenya.

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