Glacial Landforms: Corrie and Arête Formation

Corrie Formation

• Snow accumulates in north-facing hollows due to increased shade, allowing prolonged snow accumulation.
• Compaction and freezing transforms snow into glacial ice.
• Gravity drives the movement of the glacier downhill.
• Plucking occurs as ice freezes onto the bedrock and pulls away fragments, steepening the back wall.
• Abrasion happens when rocks embedded in the ice grind the hollow, deepening it.
• Rotational slip further deepens the hollow.
• At the front, friction causes ice to slow down, forming a rock lip.
• Rainwater collects behind the lip.
• Melting ice leaves a characteristic armchair-shaped hollow, called a corrie.
• Example: Red Tarn.

Arête Formation

• Corrie formation occurs first, in tandem with the formation of a second corrie.
• Plucking deepens the slopes and walls of the corrie, drawing the corries closer together.
• The resulting ridge is sharp and knife-like, known as an arête.
• Freeze-thaw weathering contributes to the sharpness after the ice age.
• Example: Striding Edge.

Pyramidal Peak Formation

• Three or more corries form around a summit.
• Plucking processes create multiple arêtes, surrounding the summit.
• Freeze-thaw weathering contributes to the sharpness of the peak.
• Example: Mount Everest.

U-Shaped Valley Formation

• Snow accumulates, solidifying into glacial ice.
• Glacial ice moves downhill due to gravity.
• Abrasion occurs as rocks within the ice grind the valley floor, causing it to deepen.
• Freeze-thaw action also steepens the valley sides by widening cracks.
• Glacial erosion transforms V-shaped valleys into wider, deeper, straighter U-shaped valleys.
• A flat valley floor and steep valley sides result from melting ice.
• Example: Glen Coe.

Ribbon Lake Formation

• Glaciers erode valleys, deepening some sections more than others.
• Glaciers can pluck and abrade rock at varying rates.
• Softer bedrock is eroded deeper than the surrounding rock.
• When glaciers melt, the deepened sections fill with meltwater.
• Terminal moraine can also act as a natural dam.
• Example: Loch Ness.

Drumlin Formation

• Drumlins are elongated hills composed of unsorted glacial deposits (till, boulder clay).
• The ice deposited the material at the same time.
• The steep "stoss end" faces up-valley, and the gentler "lee slope" faces down-valley.
• Drumlins form when sediment becomes too heavy for the glacier to carry.
• As the glacier flows, it shapes the sediment into streamlined mounds.
• Small obstacles can act as trigger points, causing material accumulation.
• Drumlin formations can occur when ice passes over deeper sediment layers.
• Increased pressure from the ice molds the sediment into drumlin shapes.
• Drumlins might be reshaped by subsequent ice movements.
• Drumlins are often found in clusters (swarms).

Terminal Moraine Formation

• A ridge across a valley, made of unsorted glacial deposits (till, boulder clay).
• Glacial movement pushes sediment in front of the glacier.
• Melting glaciers deposit the moraine.
• This marks the furthest extent of the glacier.
• Can act as a dam, creating ribbon lakes.

Esker Formation

• Winding ridges along valley floors, formed by meltwater streams.
• Forms within ice-walled tunnels at the base of the glacier.
• Composed of sands and gravels, carried by meltwater streams.
• Streams lose power and deposit the material along the riverbed.
• Larger particles are deposited first, smaller particles are carried further.
• The deposits are sorted.
• Stones are more rounded (attrition).
• Eskers are visible when the glacier melts.

Explore the fascinating processes behind the formation of corries and arêtes. This quiz delves into how snow accumulation, glacial movement, and erosion shape these stunning features in the landscape. Test your knowledge of glacial geology and understand the impact of natural forces.