ANSWER SHEET
Look at Figure 1, which shows the area in front of a glacier, with features produced
by glacial deposition.
(i) Describe how landform X was formed.
Terminal moraine (landform X) is formed in two ways:
Ablation was equal to accumulation for a long period so the glacier
snout was stationary at the maximum extent of the ice. The glacier
continuously moved forward bringing debris to the snout where the ice
melted, the debris dropped out and it accumulated as a ridge.
As the snout retreated in summer because ablation was greater than
accumulation, debris was dropped on to the ground.
In winter, the snout advanced because accumulation was greater than
ablation.
The advancing snout bulldozed the debris to form a ridge at its
maximum extent.
(4 marks)
(ii) Choose one of the landforms Y or Z from Figure 1. Describe your chosen
landform and explain how it was formed.
Landform chosen ________________________
[3 x level II are needed for 6 marks]
Y – Drumlin [first choice of landform]
Description:
A drumlin is an egg-shaped hill with a steep stoss side and a gentle lee
side. It is made of lodgement till – compressed clay with angular
clasts in it. On a map they are arranged in an en echelon pattern
with the blunt end at the stoss side and the pointed end at the lee
side. They are 500 m long, 30 m high and 200 m wide.
Explanation:
They are formed where a fast-moving glacier flows into a wider valley
and spreads out. Two theories are:
1. The ice sheet has fast, clean ice flowing over slow dirty ice.
The fast ice moulds the irregular boundary between them into
streamlined “hills.” Pressure melting of the dirty ice deposits
moraine onto the ground and the streamlined boundary is
preserved to form drumlins.
2. Dirty ice deposits wet moraine underneath it by pressure
melting. A colder climate causes more ice accumulation so
the glacier speeds up and moulds the moraine under it into the
streamlined drumlin shapes. This explains why the elongation
ratio (length/width ratio) of drumlins is proportional to the
speed of the glacier which deposited them.
Z – Medial moraine [second choice of landform]
Medial moraine e.g. at Gigjokull in Iceland
Length 5 km; height 10 m; width 100 m
A medial moraine is a long, narrow, low ridge extending along a
valley floor in the direction of the valley and glacier flow.
Explanation:
Write all the explanation for lateral moraine first then you must
include the following:
When a tributary glacier joins the main valley glacier, the two
adjacent lateral moraines are joined to form a medial moraine.
(6 marks)
(iii) What does recessional moraine tell you about ice movement?
It shows the glacier snout was stationary or advanced for a short time
during the overall retreat.
The size of the recessional moraine shows how long the glacier
snout was stationary.
The distances between recessional moraines show the rate of
retreat of the glacier.
(4 marks)