Glaciation - Physical Flashcards
What is abrasion?
Where bits of rock stuck in the ice grind against the rock below the glacier, wearing it away. (Sandpaper effect)
What is plucking?
When meltwater at the base, back or sides of a glacier freezes onto the rock. As the glacier moves forward it pulls pieces of rock out
What is freeze thaw weathering?
1) . Where water gets into cracks of rock
2) . The water freezes and expands, putting pressure on the rock.
3) . The ice thaws, releasing the pressure. If the process is repeated it can make bits of rock fall off
What are the characteristics and processes of glacial movement?
1) . Glacier ice forms snow that has been compressed, into granules of ice
2) . As weight of the ice accumulates, gravity causes it to flow over and down the mountains
3) . The surface of the glacier cracks as the glacier move over the uneven valley floor
4) . Glacier slides over the underlying rock in a process called basal flow. The ice changes the way it moves in response to the changes in the gradient of the slope; this is internal deformation.
5) . As glacier moves down, the sides and valley floor are eroded by plucking and abrasion. As a result, a big amount of eroded material are left on the floor, this is callard ground moraine
6) . In lowland areas, the climate is warmer. As ice flows it begins to melt
7) . Then end point of the glacier is called the snout. Large amounts of meltwater pour off the snout and can carry debris beyond here
What is an Arête?
Narrow, steep sides ridges formed when glaciers flow in parallel valleys. The glaciers erode the sides of the valley, which sharpens the ridge between them giving it a jagged profile
What is a pyramidal peak?
A pointed mountain peak with at least three sides. Its formed when three or more back to back glaciers erode a mountain
What are truncated spurs?
Cliff like edges on the valley side formed when ridges of land (spurs) are cut off as the glacier moves past
What are hanging valleys?
Valleys formed by tributary glaciers that flow into the main glacier. The glacial trough eroded much more deeply by the large glaciers, so when the glacier melts the valleys are left a higher level.
What are glacial troughs?
Steep sided valleys with flat bottems. They start off as a v-shaped river but change to a u-shape as the glacier erodes the sides and bottom with processes including abrasion making it wider and deeper.
What are ribbon lakes?
Long, thin lakes that form after a glacier retreats. They form in hollows where softer rock was eroded more that the surrounding harder rock
What are corries?
Begin as hollows containing a small glacier. As ice moves by rotational slip, it erodes the hollow into a steep sided shape with a lip at the bottem end. (When ice melts it can leave a small circular lake called a tarn)
What is transportation?
When glaciers move material over very large distances.
What is bulldozing?
When material is frozen in the glacier, on the surface or pushed in front of it; basically when ice pushes loose material ahead of the glacier
What is till?
as a glacier slowly retreats it leaves behind a bed broken rock fragments called till
What is deposition?
When the ice carrying the material melts, the material is deposited on the valley floor; mostly occurs at the snout
What are most glacial deposits not?
Not sorted by size and weight
What is outwash?
Very fine material such as sand and gravel can get washed away by small meltwater streams;
- the sediment is well sorted with bigger rocks being depositied closer to the ice and finer material carried many KM’s away.
What is moraine?
Landforms made out of till dropped by the glacier as it melts
What is lateral moraine?
Forms at the edge of the glacier. It is mostly scree material that has fallen off the valley sides due to freeze-thaw weathering. When ice melts the moraine forms a low ridge on the valley side
What is medial moraine?
When a tributary glacier joins the main glacier, two lateral moraines will merge to produce a single line of sediment that runs down the centre of the main glacier.
- On melting, the medial moraine forms a ridge down the centre of the valley
What is terminal moraine?
Huge amounts of material pile up at the snout of the glacier to form a high ridge. This represents the furthest extent of the glacier’s advance.
- As the ice melts & retreats up the valley, these festures are eroded from the valley floor and depositied as semicircular mounds as ice retreats
What is ground moraine?
The eroded material dragged underneath the glacier and left behind when the ice melts, often forms uneven hilly ground
What are drumlins?
Smooth egg shaped hills that are found in clusters on the floor of a glacial trough
How are drumlins formed?
They’re made of moraine that has been streamlined and shaped by the moving ice, they usually have blunt end which faces up valley and a more pointed end facing down valley. This indicates the direction of movement of a glacier
