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Ice
Valley Floor3. Rocks scrape along the
valley floor and erode it.
2. Glacier moves
This type of erosion is called abrasion.
1. Rocks frozen into glacier ice.
Glacial Erosion
Glacial Erosion
Ice
Rock
1. Ice freezes around bits of rock1. Ice freezes around bits of rock
2. The Glacier moves
3. Bits of rock are taken from the rock face with the ice
This type of erosion is called plucking
Formation of a Corrie
• Mention what the shape was like before
• Mention what the shape is like afterwards
• Mention how the shape was changed
How to answer the question:
‘Explain how a corrie was formed.’
Before Glaciation
• Snow falls in a hollow high in the mountains
• The snow compresses into ice
During Glaciation• The ice moves downhill
as a glacier
A
B
C
For full credit marks mention how abrasion, plucking & freeze thaw work
•At ‘A’ freeze thaw weathering makes the backwall steeper and jagged
•At ‘C’ abrasion deepens and smoothes the hollow
•At ‘B’ plucking makes the backwall steeper and jagged
After Glaciation
• The corrie has steep sides and steep back wall
• The hollow is deeper
The lip is The lip is emphasiseemphasised by d by moraine moraine deposited deposited by the by the glacierglacier
Often Often water fills water fills the corrie the corrie known as a known as a tarntarn
1. Two Glaciers erode back to back into a mountain by plucking as they move downhill.
2. This forms 2 corries.
3. Plucking makes the ridge narrower and this is called an Arete.
4. Freeze-thaw weathering makes the Arete sharper
1. Where glaciers start in a hollow they move downhill and erode by plucking and abrasion to form corries.
2. Three or more corries form back to back or side by side
3. Where the corrie sidewalls meet they form ridges which become narrower by plucking.
4. These are called Aretes. Three Arêtes meet to form a pyramidal peak
5. The peak becomes sharper by freeze-thaw weathering
Formation of U-shaped valleyBefore glaciation a v-shaped valleyDuring the ice age a glacier moves down the valley.
Rocks trapped in the bottom of the ice act like sandpaper wearing away the valley by abrasion.
The glacier deepens, straightens and widens the valley by abrasion.
After the ice melts a U-Shaped valley remainsAfter Glaciation there is sometimes a mis-fit stream or ribbon lake in the bottom of the valley
1. Erosion in the main glacier is far greater making a deeper valley.
2. Erosion in the tributary glaciers is less making a shallower valley.
3. The shallower valleys are left ‘hanging’ above the deeper main valley.
4. Waterfalls often fall over the edge at the end of the hanging valley into the main valley.
5. At the base of a waterfall alluvial fans are sometimes found as a result of deposition
Map View
Main valley
Tributary valley
Cross Section
Main valleyTributary
valley
Ribbon Lakes1. Glaciers move down a former v-shaped valley
and erode the valley by abrasion and plucking turning the valley into a u-shape.
2. Some ribbon lakes form when the glacier meets softer rock.
3. The glacier erodes more deeply at these points. 4. After the glacier has melted the deeper parts fill
with water to form ribbon lakes
Side view of valley before Glaciation
Side view of valley after Glaciation
Hard Rock Soft Rock
Hard Rock
Hard Rock
Hard RockSoft Rock
Ribbon Lake
How Till is formed1. The temperature rises due to climate change at the end of
the ice age or the temperature rises as the glacier reaches lower land.
2. The glacier begins to melt. The snout moves back up the valley.
3. The melting ice cannot hold the rocks, gravel and sand that have been trapped in it.
4. All this material is deposited as the glacier continues to melt. 5. The moraine is all mixed up with different sizes of material. 6. Where the glacier has been it leaves behind moraine on the
floor of the valley called ground moraine, till or boulder clay.
Melting Glacier TillOutwash Plain
Terminal MoraineDrumlins
How Drumlins are formed1. The temperature rises due to climate change at the end of the
ice age.2. The glacier begins to melt. The snout moves back up the
valley. 3. The melting ice cannot hold the rocks, gravel and sand that
have been trapped in it. 4. All this material is deposited as the glacier continues to melt. 5. The moraine is all mixed up with different sizes of material. 6. A large rock is deposited and traps more moraine around it
forming a drumlin7. The glacier continues to move when it is melting and makes
the drumlin smooth
Melting Glacier TillOutwash Plain
Terminal MoraineDrumlins
How Terminal Moraine is formed1. The glacier pushes the moraine in front of it like a bulldozer2. The temperature rises due to climate change at the end of
the ice age.3. The glacier begins to melt. The snout moves back up the
valley. 4. The melting ice cannot hold the rocks, gravel and sand that
have been trapped in it. 5. All this material is deposited as the glacier continues to melt. 6. The moraine is all mixed up with different sizes of material7. The furthest point the glacier reached is marked by a ridge
of material running across the valley called terminal moraine
Melting Glacier TillOutwash Plain
Terminal Moraine
Melting Glacier TillOutwash Plain
Terminal MoraineDrumlins
How the outwash plain is formed1. The temperature rises due to climate change at the end of
the ice age.2. The glacier begins to melt. The snout moves back up the
valley and melt-water streams carry material down the valley.
3. The outwash plain is in front of where the glacier has been and is deposited by melt-water.
4. The outwash plain is made from sorted sands and gravels.5. Gravels are deposited in the spring when there is more
melting. Sands are deposited in the autumn when there is less melting
Melting Glacier TillOutwash Plain
Ter
min
al M
ora
ine
Drumlins
How an esker is formed
1. The temperature rises due to climate change at the end of the ice age.
2. The glacier begins to melt.3. Tunnels form in the melting ice4. Meltwater streams flow in the
tunnels 5. Deposits are laid down along
the course of where the stream has been.
6. The snout moves back up the valley
7. Long, winding ridges of sorted material known as eskers are left where these streams have been
8. Gravels are deposited in the spring when there is more melting. Sands are deposited in the autumn when there is less melting
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