3. Landscapes Flashcards
How do glaciers form?
Glaciers form when hollows high in the mountains fill with snow and compress over time, forming ice. When the ice begins to move down the mountain due to gravity and rotate, in a process known as rotational slip, abrasion and plucking occur on the mountain.
The mountainside above the mountain is also being weathered, by a process known as freeze thaw.
What is abrasion?
Abrasion is when pieces of rock in the glacier, know as moraine, scrapes against the mountainside, eroding it
What is plucking?
When the glacier is flowing over rock, some can stick to it and rip it up
What is freeze thaw?
Freeze thaw occurs when water gets into a crack in the mountainside, freezes, and expands. This causes ricks to start to break away, falling on top of the glacier
How are corries formed?
When a hollow high in the mountain fills with snow and compacts into ice, a glacier forms. Gravity causes the glacier to begin to move down the mountain, rotating, in a process called rotational slip. This increases the rate of erosion in the bottom of the hollow due to abrasion. The back wall is eroded through plucking, and is fed rock from freeze thaw occurring at the top of the mountain. Once the ice has melted the hollow is over deepened, with a steep back wall, smoothed because of abrasion. The corrie will have a smooth lip where the glacier left, and may have a small lake known as a tarn
How are arêtes and pyramidal peaks formed?
The feature starts with a glacier forming on a mountainside. As it moves abrasion and plucking erode the hollow into a Corrie. If two corries form next to each other and erode back into the mountain, a narrow ridge will appear between them. This is an arête. If a mountain has three or more corries it will have multiple arêtes. These arêtes all meet at a jagged point, called the pyramidal peak. This continues to be eroded by freeze thaw today
What is the formation of a U-shaped valley?
Prior to the ice age a valley is V-shaped with interlocking spurs. During an ice age a glacier will fill this valley, and will be in contact with all sides of the valley floor. As it moves abrasion and plucking will occur on all parts of the valley. Over 1000s of years the valley floor will widen, deepen and be straightened. When the glacier retreats it will be U-shaped with steep walls, truncated spurs, flat floor, and a shallow gradient. The valley may have a ribbon lake or a misfit stream.
What are constructive waves?
Constructive - Waves which bring materials into a beach and leaves it there, because the backwash is weak
Destructive - Waves which have a very powerful backwash, so takes material off the beach
How do cliffs and wave-cut platforms form?
When the sea attacks a weakness in the base of a cliff, it will erode a wave cut notch through the processes of corrasion and hydraulic action. The wave cut notch creates an overhang in the cliff, which, due to weathering at the top of the cliff, will eventually collapse. This material will be worn down by the process of attrition. During a low tide, the base of the old cliff can be seen, which is known as a wave cut platform
What is corrasion?
When waves throw pebbles at the cliff, weakening it.
What is hydraulic action?
Hydraulic action is where waves squeeze air into cracks in the cliff, weakening these cracks further
What is attrition?
When the sea grinds down rocks
How are headlands and bays formed?
When an area has a mixture of hard rock (granite) and soft rock (chalk), the sea will erode both through the processes of corrasion, hydraulic action, and solution. However, the soft rock will erode at a far quicker rate, creating a bay between to layers of hard rock, the headlands
E.g. Swanage bay, Dorset
How do natural arches, stacks and stumps form?
When a headland is eroded from both sides by the sea. First, is will attack a weakness in the rock, through hydraulic action and abrasion. Over time this crack will widen into a cave, which the sea can get into to deepen. The cave will, over time, erode all the way through to create an arch (e.g. Durdle Door, Dorset). As the arch is unsupported and weathered by freeze thaw, it will eventually collapse into a stack. The base of the stack is attacked by the waves, and will soon topple over, it is then called a stump
What is longshore drift?
When the prevailing wind hits the beach at an angle, so does the swash. However, the backwash always retreats at a right angle to the shore, due to gravity. This means the sand will be moved along the coast, sometimes extending the beach
