Chapter 13: Glacial Processes,
Patterns and Associated Landforms
Glaciation
• Earth once covered with glaciers
• Last glaciation ended around 10,000 years ago
Chapter 13: Glacial Processes, Patterns and Associated Landforms
Glaciers
• Rivers of ice that move slowly
• Move downslope under the influence of
gravity and the pressure of own weight
• Form where rate of accumulation of
snow and ice is greater than rate of
melting
• Largest reservoir of fresh water on Earth
Chapter 13: Glacial Processes, Patterns and Associated Landforms
Types of glaciers
1. Valley glaciers: form in mountainous
locations and move down valleys
2. Continental ice sheets/glaciers: enormous
areas of glacial ice and snow
Chapter 13: Glacial Processes, Patterns and Associated Landforms
Causes of an ice age
• Change in the Earth’s orbit around
the sun
• Change in the angle of the Earth’s
axis
Chapter 13: Glacial Processes, Patterns and Associated Landforms
Processes of glacial erosion
Glaciers erode the landscape they
travel over in two ways:
1.Plucking
2.Abrasion
Chapter 13: Glacial Processes, Patterns and Associated Landforms
1. Plucking
• Bottom of glaciers scrape along valley floors –
creates friction causing melting around the
base of the glacier
• Meltwater refreezes
• Freezes around the rocks on the valley floor
and these become part of the glacier
• Glacier moves
• Newly trapped rock is plucked out of the valley
floor
• New material is then used in process of
abrasion
Chapter 13: Glacial Processes, Patterns and Associated Landforms
2. Abrasion
• bedrock beneath the glacier is eroded by
the debris/material embedded in the sides
and bottom of the glacier
• ‘Sandpaper effect’ – scrapes the rock over
which it is travelling and leaves scratches
or grooves in the rock
• Striations – show the direction of the ice
flow
Chapter 13: Glacial Processes, Patterns and Associated Landforms
Factors affecting the rate of glacial erosion
• Thickness of ice
• Topography
• Geology
• Gradient
• Accumulation and ablation
Chapter 13: Glacial Processes, Patterns and Associated Landforms
Landforms of glacial erosion (Features of erosion)
1. Cirque
• Birthplace of a glacier
• Three steep sides
• Also called a corrie or coom
2. Arête
• Narrow ridge
• Formed when two cirques formed side-byside or back-to-back
Chapter 13: Glacial Processes, Patterns and Associated Landforms
Landforms of glacial erosion (continued)
3. Pyramidal peak
• Peak at top of mountain
• three or more cirques are eroded backto-back around the sides of a
mountain…leaving a peak
Chapter 13: Glacial Processes, Patterns and Associated Landforms
Landforms of glacial erosion (continued)
4. U-shaped valley
• Glacier moves through this valley, changing the
shape from a V-shape to a U-shape
• Valleys have steep sides and flat floors
• Glacier cuts off interlocking spurs of the Vshaped valley leaving truncated spurs
Chapter 13: Glacial Processes, Patterns and Associated Landforms
Landforms of glacial erosion (continued)
5. Ribbon lakes
• Long, narrow lakes found in glaciated Ushaped valleys
• meltwater and rainwater accumulates
forming a ribbon lake
6. Fjords
• Drowned U-shaped valleys
• Result of melting glaciers
Ribbon lake
Cirque/lake
U-shaped valley
Hanging valley
Pyramidal peak
Arete
Chapter 13: Glacial Processes, Patterns and Associated Landforms
Glacial deposition
•
Dropping or laying down of sediment that was once
transported by a glacier
•
Occurs in lowland areas
•
Deposited material is called glacial drift
•
Material deposited directly by ice is called till or
boulder clay
•
Material deposited by glacial meltwater is known as
fluvio-glacial deposits
Chapter 13: Glacial Processes, Patterns and Associated Landforms
Examples of landforms of glacial deposition
•
Moraines
•
Drumlins
•
Erratics
Chapter 13: Glacial Processes, Patterns and Associated Landforms
Examples of landforms of fluvio-glacial deposition
• Eskers
• Outwash plains
• Kames and kettleholes
Chapter 13: Glacial Processes, Patterns and Associated Landforms
Landforms of glacial deposition
1. Moraine
• Deposited debris
• Various sizes ranging from large boulders
to fine rock flour
• Material may be angular or rounded in
shape
Chapter 13: Glacial Processes, Patterns and Associated Landforms
Five types of moraine
I.
Lateral moraine
II. Medial moraine
III. End/terminal moraine
IV. Ground moraine
V. Englacial moraine
Chapter 13: Glacial Processes, Patterns and Associated Landforms
Landforms of glacial deposition
2. Drumlins
•
Oval-shaped hills consisting of boulder clay
•
Show direction of glacier movement
•
Occur in swarms or cluster
•
‘Basket of eggs’ topography
•
‘Drowned drumlins’ – as the ice melted sea
levels rose and the drumlins appear as islands
in the sea
Chapter 13: Glacial Processes, Patterns and Associated Landforms
Landforms of glacial deposition
3. Erratics
•
Material transported by the glacier and are
said to be ‘out of place’ when deposited
•
Esker – long winding ridges of stratified sand
and gravel that wind its way across lowland
areas
Chapter 13: Glacial Processes, Patterns and Associated Landforms
Landforms of glacial deposition
4. Outwash plains
•
Glaciers melt
•
Release vast amounts of water
•
Spreads outwards beyond the end/terminal
moraine
•
Carries large volumes of rock and gravels and
sands
Chapter 13: Glacial Processes, Patterns and Associated Landforms
Landforms of glacial deposition
5. Kames
•
Piles of sediment consisting of gravels and
sand
•
Deposited along the front of a retreating
glacier
Chapter 13: Glacial Processes, Patterns and Associated Landforms
Landforms of glacial deposition
6. Kettle holes
•
Blocks of ice separate from the main glacier
•
Buried partly in meltwater sediments
•
Blocks of ice melt leaving depressions or holes
•
Fill with water – form kettle hole lakes