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How are glaciated upland mountain features formed?

Part of GeographyGlaciated upland landscapes

Quick version

There are three key features of mountains in glaciated uplands:

  • corrie: a large hollow on the side of a mountain formed by glacial erosion
  • arête: a knife edge ridge formed when two corries run back to back
  • pyramidal peak: formed where three or more corries and arêtes meet
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How are corries, arêtes and pyramidal peaks formed?

Video - Glaciated mountain erosion

In this video, you can learn about the erosion processes that form corries, arêtes and pyramidal peaks in glaciated upland landscapes.

Erosion processes form corries, arêtes and pyramidal peaks

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How are corries formed?

Corries formed when large amounts of snow built up on the sides of mountains.

Here is the step-by-step process of glacial erosion that forms a corrie:

  • Snow gathers in mountain - especially north facing hollows - it builds up and compacts to ice.
  • As the ice moves downhill it sticks to the back wall and rock from the surface, steepening them.
  • action also loosens rocks on the back wall.
  • Ice moving with loose rock acts like sandpaper and deepens the hollow by .
  • Ice in a corrie has a movement which means that the front of the corrie is less eroded and a lip forms.
  • The glacier melts, often leaving a also known as a corrie loch.
Corrie and lake high in the Black Cuillin mountains
This corrie can be found high in the Black Cuillin mountains on the Isle of Skye. (Photimageon / Alamy Stock Photo)
Cross section of a corrie. A steep back wall and hollow is filled with snow and ice. An arrow follows the path the ice takes down, plucking occurs, then rotation and abrasion, deepening the corrie up to the corrie lip.
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How are arêtes formed?

What is an arête?

An arête is a knife-edge ridge.

How is it formed?

  • Two corries form back to back.
  • As the glaciers erode the back walls of a corrie get closer and closer, forming a *ridge.
  • Continued erosion makes the ridge narrower with steeper edges.
The Carn Mor Dearg arête leading up to the summit of Ben Nevis
Many mountain climbers like to scramble along these steep ridges, like the Càrn Mòr Dearg arête in the Scottish highlands. (Tim Geach / Alamy Stock Photo)
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How are pyramidal peaks formed?

Here is a step-by-step list explaining how a pyramidal peak is formed:

  • A pyramidal peak is formed where three or more corries and arêtes meet.
  • Glaciers erode backwards towards each other, carving out the rocks by plucking and abrasion.
  • Freeze thaw weathers the top of the mountain, creating a sharply-pointed summit.
Pyramidal peak, Buachaille Etive Mòr
This is the pyramidal peak of Buachaille Etive Mòr in the Highlands. (David Dennis / Alamy Stock Photo)
Formation of a pyramidal peak
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Sample questions

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

Question 1

How is a corrie formed?

Question 2

How is a pyramidal peak formed?

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Quiz

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Recap

There are three key features of mountains in glaciated uplands:

  • corries: a large hollow on the side of a mountain formed by glacial erosion
  • arêtes: a knife edge ridge formed when two corries run back to back
  • pyramidal peaks: formed where three or more corries and arêtes meet
A highlighter pen and sheet of writing with sections highlighted
Cross section of a corrie. A steep back wall and hollow is filled with snow and ice. An arrow follows the path the ice takes down, plucking occurs, then rotation and abrasion, deepening the corrie up to the corrie lip.
Formation of a pyramidal peak
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