Glaciation Flashcards
(32 cards)
what are glaciers
large ‘rivers’ of ice
how do glaciers form
Glaciers are formed in high land when the climate is cooler and most of the precipitation falls as snow.
The snow accumulates and over time is compressed into ice.
When the glacier is large enough it will move downhill under its own weight and the force of gravity.
What was the Pleistocene?
the last ice age
When did the Pleistocene occur?
between 11,800 and 2.58 million years ago
Name some of the areas of Europe affected by glaciers during the Pleistocene
scotland, england, denmark, belgium, germany
explain, in detail, the process of freeze-thaw.
water seeps into gaps into rocks and when the temperature drops the water expands as it freezes, this applies pressure to the rock this process repeats and repeats until the rock is so weak that it breaks apart
What other terms are used to describe freeze-thaw
Frost shattering, nivation
how does plucking occur
Plucking occurs along the base and sides of the glacier
Glaciers freeze onto rock surfaces
When they begin to move downhill under their on weight and the force of gravity, they tear pieces of rock away with them
how does abrasion occur
Abrasion also occurs along the base and sides of the glacier.
It is the sandpapering effect of the glacier and the rocks frozen to its base.
When the glacier travels along the land, the rocks frozen to its base scrape away at the land underneath.
what is a corrie
A corrie is a bowl shaped hollow on a mountainside.
how does a corrie form
At the beginning of the ice-age the temperature dropped
Snow collected in north-facing hollows on mountainsides, where conditions were cooler.
As layer upon layer of snow was laid down, it was compressed into ice
Under its own weight and the force of gravity, the glacier began to move downhill in a rotational fashion.
As it did so it plucked rock away, steepening the back wall of the hollow.
Meanwhile, abrasion deepened the hollow where the glacier was thickest and heaviest.
The glacier lost strength as it moved up and out of the hollow. This left behind a notch of rock at the entrance of the hollow, called a rock lip.
Loose rock, soil, gravel and clay was bulldozed forward at the snout of the glacier (the front of the glacier).
This formed a terminal moraine at the entrance to the corrie.
At the end of the ice-age the glacier melted
The terminal moraine sealed in the meltwater to form a corrie loch called a tarn
what is an arete
Arêtes are knife-edged ridges.
how does an arete form
They are formed when two corries adjacent to each other erode back into the mountain.
This narrows the area of land between them.
When describing or explaining how arêtes form, you must first describe or explain the formation of a corrie
what is a pyramidal peak
Pyramidal peaks form where three or more corrie glaciers erode back to back on a mountainside.
how does a pyramidal peak form
When the corrie glaciers erode their backwalls, they create arêtes. They also narrow the peak between each corrie.
This forms a mountain peak that is roughly pyramidal in shape.
Where glaciers are unable to cover the peak, nivation sharpens this. This will continue after the ice-age. It enhances the pyramidal shape.
how do U-Shaped valleys form
At the beginning of the ice-age precipitation fell as snow.
This collected and was compressed together to form crystallised snow called firn or néve. Further compression turned it into ice.
Under its own weight and the force of gravity the glacier began to make it way downhill through a pre-existing V-shaped valley.
Freeze-thaw weathering weakened the rocks in the area. Water seeped in to cracks and fissures in the rock. During cold weather it froze and expanded putting pressure on the rock. It then thawed and the rock contracted slightly. The process happened over and over again, until the rock was so weakened it broke apart.
The glacier froze to the valley sides and then as it began to move again it plucked pieces of rock away from the sides.
Rocks frozen to the sides of the glacier also scraped away at the land.
This helped to truncate (cut-off) the interlocking spurs, thus steepening the valley sides, widening the valley and straightening it out.
Plucking and abrasion also occurred along the valley floor. Abrasion was greatest where the glacier was heaviest. This helped to deepen the valley.
how does a ribbon lake form
In some areas on the floor of U-shaped valleys, the rock may be weaker.
At those points glaciers were able to erode more deeply. They were also able to erode more deeply where glaciers were thicker and heavier.
This created elongated hollows along the floor of the valley.
When the glaciers melted those hollows filled with the meltwater to form lakes.
The meltwater was sealed in by terminal moraine.
Glaciers plucked and abraded materials such as sand, clays, boulders and gravel as they travelled. They then carried this material along with them. Where it was bulldozed forward at the snout of the glacier and then left as a ridge across the entrance to a U-shaped valley, it formed a terminal moraine.
As the hollows were typically long and thin in shape, the lakes are referred to as ribbon lakes
how do hanging valleys form
Hanging valleys were formed where a smaller tributary glacier formed above the main valley glacier.
Those smaller glaciers were not able to erode to the same width and depth as the main valley glacier.
They therefore formed a smaller glacier that hangs above the main valley glacier.
NB: When describing and/or explaining the formation of a hanging valley, you must first describe and/or explain the formation of a U-shaped valley.
how does a truncated spur form
Truncated spurs are the flat, steep valley sides of a u-shaped valley.
Before the ice-age valleys were narrow river V-shaped valleys with rounded, gently sloping hills.
The foot of the hills formed interlocking spurs (areas of land that jutted out and that the river wound round because it did not have the erosive power to remove them).
During the ice-age glaciers eroded those interlocking spurs.
At times the glacier would freeze onto the spurs and then as it started to move downhill would pluck pieces of rock away.
Abrasion occurred where rocks frozen to the base and sides of the glacier scraped away at the interlocking spurs in a sandpapering motion.
As a result of this the ends were removed from the interlocking spurs, truncating them.
This gave the sides of the U-shaped valley a steep, flat sided appearance.
Where erosion was greatest, crags and cliffs formed.
explain why glaciated uplands are ideal places for water storage and supply.
Upland glaciated areas often have relief rainfall that provides plenty of surface drainage (rivers, streams and lakes).
The ribbon lakes that form in U-shaped valleys are natural reservoirs that store vast quantities of water.
Rivers and lakes can be dammed. This allows water to collect behind the dam, creating artificial lakes where a river has been dammed or allowing more water to collect in natural lakes.
This water can be used to provide a water source for housing, industry, services, etc. in nearby towns and cities.
explain why glaciated uplands are ideal places to generate renewable energy.
Steep slopes pull water downhill rapidly under the force of gravity. This can generate electricity in hydroelectric power stations.
High exposed areas get plenty of strong wind. This makes them ideal sites for wind farms.
Explain, in detail, three advantages (positive impacts) and three disadvantages (negative impacts) of water storage and supply in glaciated uplands.
Dams built over rivers to create lochs for water supply and HEP that will flood vast areas. This will have obvious negative impacts on wildlife habitats e.g. nesting sites for birds.
Dams reduce the flow of water downstream and this can affect insect species that lay their eggs in water. This can in turn affect fish and other animals that feed on the insect eggs and larvae.
Dams can affect the migration of fish, such as salmon, reducing numbers as the fish cannot reach their breeding sites.
Dams provide essential water supplies and energy for nearby towns and cities. This allows industrial development, increasing employment. During construction the dams also provide employment opportunities. Wind farms also provide energy. Both HEP and wind energy are clean and renewable.
Explain, in detail, three disadvantages (positive impacts) and three disadvantages (negative impacts) of renewable energy in glaciated uplands.
Wind farms have been known to kill birds. Many endangered raptors such as red kites and eagles live in those upland areas. Wildfowl often fly over those areas when they migrate south for the winter. They can fly in to the turbines at times of poor visibility this kills them.
The noise and flickering effect given off by wind turbines has been proven to affect peoples health. This could impact on people living close to the turbines.
People living in areas where there are HEP stations and wind farms can be provided with cheaper power supplies.
Explain, in detail, three advantages (positive impacts) and three disadvantages (negative impacts) of forestry in glaciated uplands.
Uniform blocks of forestry containing the same species of trees can look unnatural and unattractive.
Planting forestry, especially non-native species can affect natural habitats in an area.
The trees absorb carbon dioxide from the atmosphere as they grow. This helps to counteract the effects of global warming.
Areas re-planted with native species can improve natural habitats.
The forestry can stabilise slopes, preventing landslides. The tree roots hold the rock and soil in place. The trees themselves absorb and intercept rainwater that can often cause landslides.
