Glaciation Flashcards
Physical environment P1
how are glaciers formed
Snow accumulated inNorth/Northeast side of mountain hollow as its sheltered from sun
Overtime snow compresses into ice from pressure
Glacier moves downhill due to own weight and gravity
processes of erosion
Abrasion
When angular rocks embedded in the ice scrape away at the valley floor
Plucking
When ice freezes into the bedrock and pulls loose rocks away from the sides
Freeze-thaw weathering
When water enters cracks in the rock and freezes, expanding and contracting which weakens the rock until fragments break off.
formation of a corrie
Abrasion is when angular rock embedded in the ice scrapes away at the valley floor.
Freeze-thaw weathering is when water in the cracks in the rocks freezes, expanding and contracting, weakening the rock until fragments break off.
Plucking is when ice freezes into bedrock, pulling loose rocks away from the sides.
Glaciers form in the north/north east side of a mountain where more snow accumulates in winter than melts in summer.
North/north east slopes are shaded from the sun so snow lies longer. Snow begins to accumulate and compresses into ice.
Glaciers move downhill due to gravity.
A bergschrund crevasse may open up at the back of the hollow allowing meltwater and rocks to get to the base of the glacier, increasing its erosive power.
Friction causes the ice to slow down at the front edge of the corrie, allowing a rock lip to form which traps rainwater.
An example of a corrie is Lochnagar
formation of arete
*All corrie points…
Three or more corries erode back to back towards each other
Freeze-thaw weathering sharpens rounded pointorm
formation of u shaped valley
Abrasion is when angular rocks embedded in the ice scrape away at the valley floor.
Freeze-thaw weathering is when water enters cracks in the rock and freezes, expanding and contracting again and again until pieces of rock are broken off.
Plucking is when ice freezes on to the sides of the valleys and pulls loose rocks out as it moves.
A glacier forms in a north/north east facing valley which is shaded from the sun. As snow compresses, it forms glacial ice. The ice then moves downhill due to gravity.
Interlocking spurs are cut off by the glacier to form truncated spurs.
When the river returns to the valley, it does not fit the width of the valley floor so is known as a misfit stream
An example of a u-shaped valley in Glencoe.
formation of ribbon lake
*All U-shaped valley points
Glacier finds it difficult to erode hard rock
Glacier easily erodes soft rock, forming a rock basin
Moraine may be deposited by glacier which will dam the lake
An example is loch Muick
formation of hanging valley
*All U-shaped valley points
After glaciation, the tributary valleys have been cut off by the main valley glacier and so are left “hanging” above the main valley.
When the rivers return, the hanging valley is usually marked with a waterfall.
what is moraine and how is it formed
Moraine is all material accumulated during glaciation (silt, clay, sand, gravel, stones, rocks) which have been picked up, moved and deposited by the glacier.
Formation of terminal moraine
Terminal moraine is a ridge across the valley, made up of till (unsorted, angular material) of different sizes.
As the glacier moves downhill it acts like a bulldozer, pushing sediment in front of its snout as it goes.
When the glacier reaches an area of higher temperature the ice at the snout melts, meaning it loses its power and deposits the till.
Terminal moraine marks the furthest extent of the glacier.
The longer the glacier stays at the same place, the more deposition, making larger terminal moraine.
The terminal moraine often dams the melting ice, to create a ribbon lake.w
hat is a drumlin and how is it formed
Drumlins are long oval ridges sculpted from unsorted glacial till.
Formation of drumlins
Drumlins are elongated hills made of unsorted glacial till.
When the glacier becomes overloaded with sediment, it deposits it, streamlining the sediment as it flows over it.
If there is a small obstacle on the ground, this may act as a trigger point and till will build up around it.
The steep ‘stoss’ slope faces up-valley and the gentle ‘lee’ side faces down-valley (the direction which the glacier was moving).
Once deposited, drumlins can be reshaped by later ice movements. Or, when temperatures rise, the ice can melt and deposit further material.
Drumlins are often found in swarms or in a ‘basket of eggs’ topography.what
what is an esker and how is it formed
Eskers are meandering ridges formed by meltwater streams in or under a glacier.
Formation of eskers
Eskers are meandering ridges along a valley floor, formed by meltwater streams in/under the glacier.
These are sorted by size - as heavier stones are deposited first by the flowing water.
The stones are more rounded than glacial till because the flowing water erodes their edges.
When temperatures rise, the glacier begins to melt, so the sub-glacial streams deposit their load in the tunnels.
As the glacier retreats, the sediment that had been deposited is lowered to the land surface where it forms a mound that corresponds to the path of the glacial river.
