Processes of glacial erosion and landforms Flashcards
What is plucking?
When a glacier freezes to rock or sediment beneath it, as gravity continues to drive glacier downslope it rips the substrate that froze to away and transports it
What is abrasion?
When rock and sediment entrained at the base of the glacier are dragged over the underlying bedrock and this causes the bedrock to be worn away. This is shown by striations and polished surfaces
Freeze-thaw weathering
A crack in a rick can fill up with water which then freezes as the temperature drops. As the ice expands, it pushes the crack apart making it larger, breaking off pieces of the rock. Found on corrie backwalls , rock accumulates on the glacier
Corrie formation
1) A hollow depends by nivation
2) Ice begins to rotate due to overlying pressure
3) Plucking of the ball wall and abrasion depends the hollow
4) This forms a steep back wall
5) Water trickles down the betgschrund, encouraging more freeze thaw
6) Erosion is less at the front due to reduced pressure
7) A rock lip is formed
8) Moraines add to a rock lip, creating a tarn
Arête formation
Corroded erode backwards through plucking and abrasion, back walls becomes steeper and a steep knife edge ridge is left over
Pyramidal peak formation
3 or more corries and arêtes meet, glaciers carve away the top of the mountain and an angular, sharply pointed summit remains
U-shaped valley formation
Corrie glacier leaves the source region and descends down the valley, scouring occurs as the glacier moves. A deep, wide, u-shaped valley is left
Ribbon lake formation
Glacier moves over alternate bands of hard and soft rock, sharp edged boulders carried at the base erode softer rock via abrasion. Rock basin is formed. Harder rock erodes less, rock bars form acting as a dam, rainwater fills up rock basin and ribbon lakes form
Hanging valley formation
Form when two glaciers meet, tributary valley is smaller with less mass, valley is eroded
Roche moutonee formation
Glacier meets resistant rock, ice advances over the rock, smooth slope is created through abrasion, ice flows down over the rock, plucking removes fragments and a jagged, rough tail is left behind
Misfit stream formation
A river too small to have eroded the valley it flows through
Truncated spur
Interlocking spurs are left behind from a river, abrasion and plucking erodes the tips of the spurs, steep-cliff like outcrops are left
Fjord formation
Located where glacial erosion happened below sea level, when the glacier retreats. Sea water fills the valley floor
