Lithosphere

Corrie Cas

Example of a corrie.

Lairig Ghru

Example of a u-shaped valley.

Fiachaill

Example of an arete.

The Angels Peak

Example of a pyramidal peak.

What are the three glacial erosional processes?

Freeze thaw, plucking and abrasion.

What is plucking?

Where ice freezes to rocks and as the ice moves is pulls out the rock.

What is freeze thaw?

Water gets in cracks and freezes putting pressure on surrounding rock. Repeated freezing and melting breaks down rock.

What is abrasion?

rocks in glaciers rubs on surface like sandpaper to smoothen it.

What is the percentage increase in size when water freezes?

9%

What is tarn?

water trapped in the base of a corrie.

What is a glacier?

A huge body of ice that move downhill carving out the landscape.

What is moraine?

Rocks trapped in, on or under a glacier.

What is scree?

Loose rock that may cover a slope that is usually formed by freeze-thaw action.

What is a misfit stream?

Stream in the base of a u-shaped valley that played no part in eroding the valley.

What is a ribbon lake?

Lake or loch is the base of a u-shaped valley.

What is an arete?

A knife like ridge between the backs of 2 corries.

What is a pyramidal peak?

A peak that has 3 or more corries around the peak.

What is a corrie?

An armchair shaped hollow in the side of a hill.

What is a bergschrund?

Large crevasse at the back of a glacier.

How is a corrie formed?

• Snow collects in a hollow on a mountain, usually on a north-facing slope where it’s colder.

• Over time, the snow compacts and turns into ice.

• The ice starts to move downhill due to gravity, acting like a glacier.

• The ice erodes the rock beneath it through plucking (where rocks are pulled out of the bedrock) and abrasion (where rocks in the ice scrape the bedrock).

• This erosion deepens the hollow and steepens the sides, creating a bowl-shaped feature.

• After the glacier retreats, the corrie often has a small lake in the bottom, called a tarn.

How is an arete formed?

• When glaciers form in two adjacent corries, they erode the land on both sides of the ridge between them.

• The process of plucking (rocks being pulled from the bedrock) and abrasion (scraping by the glacier) deepens and steepens the sides of the corries.

• As the glaciers erode the land, the ridge between them becomes narrower and steeper, forming a sharp, pointed ridge called an arete.

• Over time, the erosion continues, and the arete becomes more distinct and knife-edged.

How is a pyramidal peak formed?

• A pyramidal peak forms when three or more glaciers erode a mountain from different sides, usually in a cirque or corrie.

• The glaciers erode the rock through plucking and abrasion, deepening and steepening the sides of the mountain.

• Over time, the mountain becomes sharper and more pointed as the glaciers continue to erode the land.

• The result is a pyramid-shaped peak, with steep slopes on all sides, surrounded by the glaciers that eroded it.

How is a u-shaped valley formed?

• A U-shaped valley is formed when a glacier moves through a V-shaped river valley.

• The glacier widens and deepens the valley through abrasion (scraping of rock) and plucking (pulling away pieces of bedrock).

• As the glacier moves, it erodes the sides and floor of the valley, turning the original V-shape into a U-shape.

• The valley floor becomes much wider and flatter, and the sides are steep.

• When the glacier retreats, the valley remains with its U-shape, often filled with glacial debris.

What is a hanging valley?

Smaller valleys that ‘hang above’ the main u-shaped valley.

How is terminal moraine formed?

• When a glacier advances, it pushes debris (like rocks and soil) in front of it, creating a ridge.

• As the glacier retreats, it leaves behind this material at its furthest point, forming a terminal moraine.

• The moraine consists of debris that was carried by the glacier, including rocks, sand, and clay.

• Over time, the terminal moraine forms a mound or ridge at the end of the valley or at the edge of a glacier's former reach.

How is esker formed?

• During a glacier's retreat, meltwater from the ice flows through tunnels beneath the glacier.

• These meltwater streams carry sand, gravel, and rocks, which are deposited along the floor of the tunnels.

• As the glacier retreats further, the tunnel is abandoned, leaving behind a ridge of material that was deposited by the meltwater.

• Over time, the sediment forms a long, winding ridge known as an esker.

How is drumlin formed?

• Drumlins are formed when a glacier moves over a region, carrying debris like sand, gravel, and rocks.

• As the glacier advances, it reshapes the land by pushing debris into a teardrop-shaped hill.

• The long, sloping side of the drumlin faces the direction the glacier was moving, while the steep side faces the receding direction.

• They usually appear in groups known as drumlin fields.