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

flow – show the direction of the ice

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-by side 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 back to-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 V shaped 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 U shaped 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