Geography - Glaciation

3 Erosional/weathering processes

• Plucking - Ice melts and refreezes. Rips rocks out of the ground as it moves (steeper)

• Abrasion - Rocks grind on the floor (smoother and deeper)

• Freeze-thaw weathering - Water gets in cracks and freezes, expanding and breaking the rock. Creates loose rock called scree (jagged and steeper)

Formation of Corrie

• Snow collects in north facing hollow and compresses into glacier

• As gravity moves the glacier downhill, the glacier plucks and abrades the hollow, steepening and deepening the hollow

• Freeze-thaw continues to steepen the backwall even after the glacier is gone

• Meltwater creates a corrie lochan held in place by the rock lip

• Scree at the back wall

• Example: Corrie Fee in the Cairngorms

Formation of Arête

• Two corries form back to back

• Creates knife-edged ridge

• Example: Curved ridge in Glen Coe

Formation of Pyramidal Peak

• Three or more corries back to back around a mountain top

• Example: Matterhorn in Switzerland and Italy

Formation of U-shaped valley

• Starts as V-shaped valley as river winding round interlocking spurs as it can’t erode.

• As temperature drops, snow accumulates and glacier forms

• Glacier moves through valley due to gravity, using plucking and abrasion to deepen, widen and steepen the valley while freeze-that works on the area with no glacier

• U-shaped valley is left with misfit stream on wide valley floor with steep sides

• Truncated spurs long the side