erosion features Flashcards
corrie
Snow accumulates in north facing hollows when more snow falls in winter than melts in the summer
North/north-east facing slopes are more shaded so snow lies longer with accumulated snow compressed into neve and eventually ice
Corries are formed by 3 processes: plucking, abrasion and freeze-thaw weathering
Plucking is when ice freezes on to bedrock, pulling loose rocks away from the backwall
Abrasion is when the angular rock embedded in the ice grinds the hollow
Freeze thaw weathering is when water in cracks in the rock freezes, expands and contracts weakening the rock until fragments break off
To form a Corrie, glaciers move downhill due to gravity
Bergschrund crevasse opens up at the back of the hollow which allows meltwater and rock fragments to get to the base of the glacier increasing erosive power
The weight of the glacier pushes down causing rotational sliding which deepens the hollow
Friction causes the ice to slow down at the front edge of the corrie,allowing a rock lip to form which traps rain water
arete
Snow accumulates in north facing hollows when more snow falls in winter than melts in the summer, north/north-east facing slopes are more shaded so snow lies longer with accumulated snow compressed into neve and eventually ice
Corries are formed by 3 processes: plucking, abrasion and freeze-thaw weathering
Plucking is when ice freezes onto bedrock, pulling loose rocks away from the backwall
Abrasion is when the angular rock embedded in the ice grinds the hollow
Freeze thaw weathering is when water in cracks in the rock freezes, expands and contracts weakening the rock until fragments break off which can make the ridge more pronounced and can cause scree slopes to develop
To form a Corrie, glaciers move downhill due to gravity
Bergschrund crevasse opens up at the back of the hollow which allows meltwater and rock fragments to get to the base of the glacier increasing erosive power
The weight of the glacier pushes down causing rotational sliding which deepens the hollow
Friction causes the ice to slow down at the front edge of the corrie,allowing a rock lip to form which traps rain water
An arête is formed when two corries erode back towards each other and create a knife shaped ridge in the middle
pyramidal peak
Snow accumulates in north facing hollows when more snow falls in winter than melts in the summer, north/north-east facing slopes are more shaded so snow lies longer with accumulated snow compressed into neve and eventually ice
Corries are formed by 3 processes: plucking, abrasion and freeze-thaw weathering.
Plucking is when ice freezes on to bedrock, pulling loose rocks away from the backwall
Abrasion is when the angular rock embedded in the ice grinds the hollow
Freeze thaw weathering is when water in cracks in the rock freezes, expands and contracts weakening the rock until fragments break off
Freeze thaw weathers the top of the mountain, creating a sharply pointed summit
To form a Corrie, glaciers move downhill due to gravity
However, for a pyramidal peak, glaciers erode backwards towards each other, carving out the rocks by plucking and abrasion
Bergschrund crevasse opens up at the back of the hollow which allows meltwater and rock fragments to get to the base of the glacier increasing erosive power
The weight of the glacier pushes down causing rotational sliding which deepens the hollow
Friction causes the ice to slow down at the front edge of the corrie,allowing a rock lip to form which traps rain water
A pyramidal peak has steep, triangular faces divided by sharp ridges or arêtes
A pyramidal peak is formed where three or more corries and arêtes meet
u-shaped valley
U-shaped valleys are created through glaciation
Gravity and the weight of the glaciers causes them to flow downhill, following existing V-shaped valleys
The glacier freezes on to bedrock and, as it moves downhill due to gravity, it pulls away large chunks of rock from the backwall - a process known as plucking
Abrasion, when the angular rock embedded in the ice grinds the hollow, making it deeper
Frost shattering when water in cracks in the rock freezes, expands and contracts weakening the rock until fragments break off
As glaciers move through a landscape, the processes of plucking and abrasion widen, steepen, deepen and smooth valleys into a ‘U’ shape
Former interlocking spurs may be cut off by the glacier as it flows downhill leaving truncated spurs and steep valley sides
The width and shape of the resulting glacial trough will depend on the rock type and the intensity and weight of the glacier
Tributary valleys have smaller less powerful glaciers which result in less deep U-shaped valleys ‘hanging’ about the main valley
After glaciation, freeze-thaw action continues with the warming and cooling of temperatures, as well as other agents of weathering
This causes rocks to weaken and fall to the valley floor as screen
hanging valley
Gravity and the weight of the glaciers causes them to flow downhill, following existing V-shaped valleys
The glacier freezes on to bedrock and, as it moves downhill due to gravity, it pulls away large chunks of rock from the backwall - a process known as plucking
Abrasion, when the angular rock embedded in the ice grinds the hollow, makes it the valley deeper
Frost shattering when water in cracks in the rock freezes, expands and contracts weakening the rock until fragments break off
The degree to which glaciers can erode down into the landscape is dictated by their size: the larger the glacier, the deeper the valley it can erode
Small glaciers can erode only shallow valleys while large glaciers can erode much deeper valleys
Hanging valleys are created through glaciation
A hanging valley is a shallow valley carved by a small glacier and thus the elevation of the valley floor is ‘hanging’ high above the elevation of the valley floor carved out by the larger glacier
ribbon lake
As a glacier flows over the land, it flows over hard rock and softer rock
Softer rock is less resistant, so a glacier will carve a deeper trough
When the glacier has retreated, (melted) water will collect in the deeper area and create a long, thin lake called a ribbon lake
A ribbon lake is a long and deep, finger-shaped lake, usually found in a U-shaped valley
A ribbon forms in a hollow when a glacier has more deeply eroded less resistant rock or it may fill up a valley behind a wall of moraine across the valley
Many of the lakes in the English Lake District are ribbon lakes, eg Windermere
The areas of harder rock left behind are called rock steps
