physical landscapes in the UK - glaciers Flashcards
relief
the shape, height and steepness of the land
geology
the rock type
ice erosion
gravity causes ice to move down a mountain which causes the rock below to erode in 2 different ways.
plucking
when ice moves over a rock, melt water will freeze in loose sections of the rock, pulling them away. This is most effective when there are many jolts or cracks in the rock for the melt water to seep into. Melt water is present at the base of the ice. This happens because the ice at the bottom melts due to the pressure from the ice above.
abrasion
Caused by rocks and boulders embedded at the base of the glacier which act like sandpaper, scraping and scratching the rock below. The larger the boulder, the more damage it will make to the rock. This scares the landscape with features called striations.
what increases the rate of abrasion
When plucking happens, more rocks and boulders will be embedded at the base of the glacier.
Freeze-thaw weathering
In glaciated areas, it takes place on rock surfaces and above the surface of ice and its margins.
what is the process of freeze-thaw weathering
Water seeps into a crack in a rock face (water from summer rainfall or snow melt). Temperature during the night will decrease and the water will freeze. As water freezes it expands by about 10%. The expansion causes the rock’s crack to prise open wider. During the next 24-hour cycle, the ice will melt and the melt water will sink deeper into the crack and freeze again. Over a period of time, large rocks can be shattered due to repeated cycles of freeze-thaw weathering.
epoch
a period of time marked by distinctive features
ice age
a period of time where there is long term cooling of the Earth’s atmosphere which causes the expansion of ice sheets and glaciers.
glaciers
a sheet of ice which moves slowly down a river valley. (often called river of ice).
ice sheets
a huge mass of ice covering landscape which moves very slowly with only the mountain peak that protrudes above the ice. It covers more than 50000 km sqrd.
what are the causes of glacial movement
gravity, weight of ice and melt water
melt water in glacial movement
melt water provides lubrication allowing the glacier to slide over the surface.
internal deformation
The weight of the ice puts pressure on ice crystals forcing them to change shape. The ice crystals act as a ‘plastic’ and flows.
rotational slip
movement of ice in a circular motion out of a hollow or corrie.
how does rotational slips work
Snowfall is collected in a hollow. As more snow falls, the snow is compressed by squeezing all the air out and making it firm. As there is pressure from the multiple layers of snow, over thousands of years it will become a glacier. Even though the glacier is in a hollow and unable to move downwards, gravity will still encourage it to. This is circular motion and the glacier will pull away from the back wall making crevasses or bergschrunds.
basal flow
when a glacier moves over a rock surface on a film of melt water
moraine
rock debris which is deposited by melt water and carried by a glacier
bulldozing
the front of a glacier is called the snout. As ice moves from upland areas to lowland areas the snout bulldozes material. Soil, rocks and boulders are shoved forward by the sheer force of moving ice.
glacial outwash
As glaciers move from upland areas to lowland areas, they enter a warmer climate zone. Melt water usually pours over the snout of some glaciers. Melt water can carry vast amounts of water from glaciers and ice sheets. Melt water rivers carry sediment. The sediment will be round and smooth due to attrition. The largest sediment will be deposited first because it’s the heaviest and requires more energy to be carried.
Attrition
when a rock rubs against another rock surface causing the rock to become smaller, rounder and smoother.
Outwash
material (normally sand of gravel) deposited by melt water in front or underneath a glacier.
Glacial Till
As a glacier moves from upland areas to lowland areas, the section of ice containing the sediment will temporarily become the snout and melts so that the sediment is deposited. This sediment will be angular and not deposited in size order, this is because the sediment was carried by a glacier and therefore didn’t have attrition or abrasion happen.
Formation of corries
