Bitesize has changed! We're updating subjects as fast as we can. Visit our new site to find Bitesize guides and clips - and tell us what you think!

Geography

Lithosphere

Landscapes of glacial erosion on an OS map

Landscapes of glacial erosion are found in the North and West of Britain including the North-west Highlands, the Cairngorms, the Lake District (Cumbria) and Snowdonia (part of the Welsh Cambrian Mountains). You should know how to describe and explain features of glacial erosion and be able to recognise them on an OS map.

Mountain features

A corrie shown from above and straight on

Corrie and tarn

A corrie is an armchair shaped hollow, high on a mountain with steep back and side walls. After glaciation, the hollow may be filled by a small lake or tarn.

Snow gathers in mountain hollows, especially north facing hollows, where there is more shade. This snow builds up and compacts to ice (neve). The action of gravity means the ice moves down the hill. As it goes, it sticks to back walls and plucks rock from the surface. Rocks on the backwalls are loosened by freeze-thaw action. A gap between the wall and the ice develops, called a bergschrund. Ice moving with loose rock acts like sandpaper and deepens the hollow by abrasion. Most erosion is where the weight of the ice is the heaviest. Stones frozen in the base of the ice grind or abrade the corrie base, deepening it. Ice in a corrie has a rotational movement which means that the front of the corrie is less eroded, and a lip forms. The glacier retreats and melts, often leaving a Tarn/glacial lake in the base of the corrie.

Arete shown from above and straight on

An arête is a narrow knife-edged ridge where two corries have eroded back to back. That is, when the back walls of a corrie have been eroded back so far that only a narrow ridge separates them.

Pyramidal peak shown from above and head on

Pyramidal peak

Pyramidal peaks or horns have a sharp summit and steep slopes on at least three sides. A pyramidal peak may form where three or more corries erode back so far that they produce aretes with a pyramidal peak in between.

Valley features

U-shaped valley, close up and from a distance

U-shaped valley

U-shaped valleys have steep sides and a wide, flat floor. They are usually straight and deep.

U-shaped valleys are formed in river valleys which, during the ice age, have been filled by a large glacier. These glaciers have deepened, straightened and widened the valley by plucking and abrasion.

Hanging valleys including truncated spurs and watefall

Hanging valleys and truncated spurs

A hanging valley is a smaller side valley left 'hanging' above the main u-shaped valley. A waterfall can often be seen. During glaciation the smaller side valley contains less ice than the main glacial valley, which is why it is not as deeply eroded.

Truncated spurs are rounded areas of land which have been cut off. They are often rounded at the top but steep at the bottom. They are formed when glaciers move through the main valley and cut off spurs.

Ribbon lakes including a misfit stream

Ribbon lakes and misfit rivers

A ribbon lake is a large, narrow lake occupying a u-shaped valley. It forms in a hollow when a glacier has more deeply eroded less resistant rock or it may fill up a valley behind a wall of moraine across the valley.

Misfit rivers meander through the flat, wide U-shaped floor. They did not erode the valley, as they formed in the valley after glaciation had carved out the U-shaped valley.

Features of glacial erosion are also covered in Standard Grade Bitesize: Glaciation.

Watch

Cliffs of Dover

Class Clips

Coastal processes and landforms.

Watch

A photo of some coastal headland

Class Clips

Wave cut platforms and stacks.

BBC © 2014 The BBC is not responsible for the content of external sites. Read more.

This page is best viewed in an up-to-date web browser with style sheets (CSS) enabled. While you will be able to view the content of this page in your current browser, you will not be able to get the full visual experience. Please consider upgrading your browser software or enabling style sheets (CSS) if you are able to do so.