Get premium membership and access revision papers with marking schemes, video lessons and live classes.

Processing. Please wait.

In this lesson we are going to discuss about the highlands and lowland features of glacial erosion

Answer Text:
Erosion Features
On Glaciated Highlands
a) Cirque

- Arm chair shaped depression on glaciated slopes of high mountains.
- Snow accumulates into a shallow depression on the side of a mountain.
- Freezing in winter and thawing in summer causes rocks to wither and break up resulting in enlargement of the hollow.
- Accumulated ice advances by slipping down slope.
- A deep crevice called bergschrund develops at the top of ice due to unequal movement.
- Freezing occur deep down the bergschrund causing the back wall and sides to be steepened by plucking.
- Plucked debris is carried forward scratching the floor of the basin deepening it forming the cirque, corrie or cwm.
-Water from melting snow may accumulate in a cirque to form a tarn e.g. Teleki tarn.
b) Arêtes
- Narrow knife- edged steep ridge separating two cirques.
- Formed when two cirques cut backwards on adjacent sides of a mountain leaving a narrow steep ridge separating them.
c) Pyramidal Peaks
- Sharp steep sided peak at the top of a mountain.
- Formed when three or more cirques erode on mountain side towards each other leaving a sharp pointed rock separating them at the top of the mountain e.g. Corydon and Delamere on Mt. Kenya.
d) Glacial Trough
Glacial Trough and Related Features

- Wide flat bottomed valley with steep sides on a glaciated highland.
- Ice accumulates in a v-shaped valley.
- Plucking and abrasion by ice occurs.
- The v-shaped valley is deepened, widened and straightened to become a glacial trough.
- Glaciated trough may be submerged to form a fiord.
e) Truncated Spurs
- Interlocking spurs of former river valleys which are eroded and straightened by valley glacier.
Erosion Features on Glaciated Lowlands
a) Roche Mountonnee
- Rock outcrop with a long smooth gentle slope on the upstream side and a rugged steep slope on the downstream
side found on glaciated lowland.
- Formed when ice acts on a rock on its way causing the side facing the upstream side to be polished by abrasion resulting
into a smooth gentle slope and the downstream side is affected by plucking resulting in a rugged steep slope leaving a
rock outcrop standing just above the surface.
b) Crag and Tail
Crag - projection of resistant rock which protects a mass of softer rock on the downstream side of the glacier.
- The ice moves over and around over the resistant rock eroding it slightly by abrasion.
- Cracks develop on the upstream side causing the ice to move and pluck materials from the resistant rock leaving a
projection of resistant rock with a steep rugged upstream side is formed.
Tail - elongated feature on the downstream side of the crag formed by formed by material deposited by the glacier on the downstream side and the
weaker rock.
c) Depressional Lakes
- Depressions filled with water from melting ice found in glaciated lowlands.
- Formed when soft rocks are scooped out by moving ice sheet forming depressions which are filled with water to form a lake.