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Home > Geography > Glaciation > Processes of glaciation

Geography

Processes of glaciation

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Types of question

In the exam, questions might say, "You may use diagrams to illustrate your answer". This is a strong hint that you should use a sketch. Without a diagram your answer will need to be very good to get full marks. With a diagram it is easier to explain and you give yourself a better chance of scoring full marks.

On the other hand, the question may say, "With the aid of a diagram explain the formation of - (for example, a pyramidal peak)" . In this case you cannot get full marks without a diagram.

Sample questions

The examples of questions that follow show ways of using diagrams to explain how the most common features were formed. Sometimes 'Before' and 'After' diagrams make it easier to explain.

As part of your revision you should practice copying these diagrams or those in your textbooks. Try to keep them as simple as possible so that you can do them quickly in the exam. Notice that sometimes the same, or very similar, diagram can be used to show different features.

Question

Explain the formation of a Corrie (Cirque). You may use diagrams to illustrate your answer.

Answer
Stages of the formation of a corrie

a) snow collects in hollows, b) snow compacts to ice, c) ice moves under gravity, lubricated by meltwater, d) ice rotates to lip, e) abrasion deepens corrie, f) plucking steepens back and sides, g) corrie lochan may fill hollow.

Question

Explain the formation of a Pyramidal Peak (Horn). You may use diagrams to illustrate your answer.

Answer
Stages in the formation of a pyramidal peak

a) three or more corries form around a peak, (processes are the same as for corries), b) where corrie sidewalls meet they form an arête (knife edge).

Question

Explain the formation of a 'U' Shaped Valley. You may use diagrams to illustrate your answer.

Answer

V shaped valley before glaciation
Glacier eroding a valley illustration
U shaped valley after glaciation

a) glacier flows in an earlier 'V' shaped valley, b) glacier abrades the sides and floor of the river valley, c) valley is greatly deepened, widened and straightened, d) when the ice melts the valley is 'U' shaped, e) it has very steep sides and a fairly flat floor, f) any later rivers are called 'misfit streams' because they are far too small to have cut the valley.

Question

Explain the formation of a Till (Ground Moraine or boulder clay). You may use diagrams to illustrate your answer.

Answer
Glacier and rock debris forming a till

a) moving glacier carries a mixture of rock debris from boulders to fine clays, b) movements within the ice cause some of these to reach the sole (underside) of the glacier, c) the weight of the ice crushes them down and the clays help to stick the till to the underlying rock.

Question

Explain the formation of a Terminal Moraine. You may use diagrams to illustrate your answer.

Answer
Glacier starting to melt forming terminal moraine

a) where ice melts at snout (front end) of glacier, b) marks point where the edge of the ice stayed steady, melting ice being replaced by new flows, c) melting ice dumps a mixture of rock debris carried on and in the ice, d) hummocky ridges build up across the ice front.

Question

Explain the formation of a Drumlin. You may use diagrams to illustrate your answer.

Answer
Glacier moves over tills forming drumlins

a) near the front of the glacier, b) moving ice moulds the till, c) forms long, low, rounded hill, d) long, half-egg shape e) broader, higher end shows direction ice came from, f) lower, pointed end shows direction ice was moving to.

Practise drawing diagrams. Copy these (print off this page and copy them off-line).

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Watch

Loch Lomond graphic

Class Clips

The formative processes of corries, pyramidal peaks, truncated spurs and hanging valleys

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