Paper 1- Section C, Uk Glacial Landscapes Flashcards
What is freeze thaw weathering
Water expands when it freezes, when water fills cracks in rocks if it then freezes, it expands putting pressure on the rock, eventually this will wear down the rock and causes the cracks to widen as the process repeats
Why is freeze thaw an important process in glacial environments
- helps shape jagged glacial mountain landscapes
- rocks become weakened by freeze-thaw making it easier for them to be eroded by glaciers
- piles of large angular rocks called scree collect at the foot of mountains, these become powerful erosion tools when trapped under moving glaciers
How far do glaciers move a year
Only a few centimetres
What are the two main types of glacial erosion
Abrasion and plucking
What is the glacial erosion abrasion
- sandpaper effect caused by weight of ice scouring valley floor
- abrasion leaves smooth, polished surface
- striations can be seen beneath the ice
Describe plucking
- Meltwater freezes and bonds to base of glacier to the rocky surface below
- as glacier moves, any loose fragments of rocks are plucked away
- this process leaves a jagged rocky surface
What two ways do glaciers move
- rotational slip and bulldozing
What is basal slip
In the summer meltwater lubricates the glacier enabling it to slide downhill and the movement can be quite sudden
What is rotational slip
The glacier moves out of the hollow in a circular motion called
rotational slip
What is internal deformation
In the winter, the glacier becomes frozen to the rocky surface, the sheer weight of the ice and the influence of gravity cause individual ice crystals to change shape and this causes the glacier to move slowly downhill
What is bulldozing
At the front of glaciers, rocks and debris are pushed downhill in a straight line
When does deposition occur
Occurs when the ice melts
Where does most of the deposition happen
At the front of the glacier
What is till
Most material carried by glaciers in the form of unsourced mixtures is till
In terms of deposition, what happens when the glacier retreats
Leaves behind a bed of broken rock fragments (till) and due to lack of water to transport, it is poorly sorted with rock fragments of all sizes
What are moraines
Landforms that are left behind after a glacier melts, they are made of till
How is lateral moraine formed
When an extended mound of till is deposited at the edge of a glacier and it is made up of material from the valley walls
How are medial moraines formed
When an extended ridge of till is deposited in the middle of a valley and is formed when 2 glaciers join
How are ground moraines formed
When till is carried underneath a glacier a ground moraine is formed and they are deposited across the valley floor
How are terminal moraines formed
Made of till that was transported at the front of the glacier and is deposited at the glaciers snout
What are corries
Large hollowed out depressions found on the upper slopes of glaciated valleys and are recognised by a steep back and raised lip and they may have a lake called a tarn
How are corries formed
- snow accumulates in a sheltered hollow on a hillside
- processes like freeze-thaw, meltwater and slumping enlarge the hollow letting more snow collect
- gradually snow turns to ice and a small corrie is formed
- rotational slip gouges out the deep hollow
- there is less erosion at the front of the corrie as the ice is thinner and less erosive so this forms a raised lip
- a tarn may form in the bottom of the corrie
What is an arête
Knife edged ridge often found at the back of a Corrie or separating two glaciated valleys, often extremely narrow
How are pyramidal peaks formed
If three or more corries have formed on a mountain, erosion may lead to the formation of a single peak, a pyramidal peak
