Features of a glacial landscape

The diagram below shows some features of a glacial landscape.

Features of the glacial landscape

  1. A pyramidal peak has steep, triangular faces divided by sharp ridges or arêtes.
  2. An arête is a sharp ridge between corries.
  3. A corrie is an armchair-shaped hollow with steep back and sides.
  4. A corrie loch, or tarn, is a body of water which has gathered in the hollow in the corrie floor.
  5. An alluvial fan is a fan-shaped pile of rock remains (alluvium) washed down by a stream and piled up where a steep valley side meets the valley floor.
  6. A ribbon lake is a long narrow lake in a part of the valley cut deeper by the glacier.
  7. A truncated spur exists because a ridge has been cut off sharply by the ice that flowed down the main valley.
  8. A misfit stream is so-called because it is far too small to have cut the valley.
  9. A hanging valley is called this because the valley floor is much higher than the floor of the main valley.
  10. A U-shaped valley has steep sides and a nearly flat floor. (The other side of the valley is missing in this cut-away diagram).

Sample questions

The sample questions that follow show ways of using diagrams to explain how the most common features were formed.

Question

How is a corrie formed?

Formation of a corrie Stage one

Formation of a corrieStage two

Formation of a corrieStage three

  • snow collects in hollows
  • snow compacts to ice
  • ice moves under gravity
  • lubricated by melt water
  • ice rotates to lip
  • abrasion deepens corrie
  • plucking steepens back and sides
  • corrie loch may fill hollow
Question

How is a pyramidal peak (horn) formed?

Formation of a pyramidal peak Formation of a pyramidal peak

  • Three or more corries are eroded backwards into the same mountain.
  • The ice steepens the back walls through plucking.
  • Abrasion deepens the hollows.
  • Freeze-thaw weathering creates a jagged peak.
  • Where corrie sidewalls meet they form arêtes (knife-edge ridges).
  • With a pyramidal peak in the middle.
Question

How is a U-shaped valley formed?

Formation of a V-shaped valleyStage one

Formation of a V-shaped valleyStage two

Formation of a V-shaped valleyStage three

  • A glacier flows in an earlier V-shaped river valley.
  • The glacier plucks rocks from the sides of the valley making it steeper.
  • And abrades the floor of the valley making it wider and deeper.
  • When the ice melts the valley has changed from a V-shape to U-shape.
  • It has very steep sides and a fairly flat floor.
  • >Any later rivers are called 'misfit streams' because they are far too small to have cut the valley.