Glaciation Flashcards
When was the last ice age in Europe and the British Isles
The last ice age in Europe and the British isles was 18,000 years ago
Europe in the Ice Age
In Europe, about 18,000 years ago, ice sheets spread down from the north as climate cooled. As well as the great ice sheets, glaciers filled and eroded the valleys
Interglacial periods
Interglacial periods are warm periods between these glaciations. Temperatures can be higher than they are today
Glacial periods
Glacial periods are ice advances, the last one ended 10,000 years ago
The Mer de Glace glacier
The Mer de Glace is an alpine glacier located on the northern slopes of the Mont Blanc massif, in the French Alps.
What is a Glacier
A glacier is a mass of moving ice
Characteristics of a glacier
Snowfall Jagged mountain peaks Cirque/Corrie Crevasses Snout Terminal moraine
High Latitude
High latitude means the glacier is closer to the poles and further away from the equator
High altitude
Away from the poles glaciers only exist in mountainous terrain. As long as the mountain is high enough there will even be glaciers close to the equator.
Glacial Advancement
When more snow falls than melts the glacier grows
Glacial Retreat
When more snow melts than falls so the glacier melts or retreats
Accumulation
accumulation is greater in the higher reaches of the glacier
Ablation
ablation is greater in the lower, warmer reaches of the glacier
How are glaciers formed
1) snowflakes collect or accumulate in a hollow in a mountainside.
2) more and more snow falls on the flakes, increasing the density or weight.
3) the increased weight compresses the snow at the bottom into solid ice.
4) If the ice doesn’t melt and the snow continues to fall, the ice mass (glacier) will become bigger and heavier. Gravity will cause it to move downhill very slowly.
Glacial Processes
Frost shattering (freeze-thaw weathering), abrasion (striations) and plucking
Frost shattering (freeze-thaw weathering)
A type of weathering where water repeatedly freezes and puts pressure on rocks to break them down. The rock will have cracks in it, then the cracks will fill with water, the rock will start to expand, finally the pressure will cause the rock to explode and then the process repeats again. The cracks in the ice are called crevasses and they are extremely dangerous.
Abrasion
Abrasion occurs when rocks and stones, picked up by the Glacier are rubbed against the bedrock at the bottom and side of the glacier, as the glacier moves downhill. This causes wearing on the landscape (sandpaper effect). This grinding leaves long grooves in the bedrock called striations or smooth polished crock (which is smooth and shiny).
Plucking
This is when rocks and stones become frozen to the base of the glacier and are plucked from the ground as the glacier moves
Glacial landforms created by erosion
Corries. Arêtes. Pyramidal peaks. Glacial troughs. Truncated spurs. Hanging valleys.
How corries are formed
1) Snow accumulates in the north and east facing hollows.
2) Snow is compacted into ice and moves downhill.
3) Frost shattering and plucking create a steep backwall.
4) abrasion deepens the hollow and forms a rock basin.
5) A rock lip is left where the rate of erosion decreased.
6) The height of the lip is increased by deposition of moraine.
7) The rock lip and moraine act as a dam
8) A corrie lake (tarn) fills the rock basin after the ice age.
What are arêtes and how are they formed
An arête is a narrow knife - edged ridge on the mountain top. Generally forms around a corrie. When two corries are formed back to back they both erode backwards until they create a narrow knife - edge ridge between them.
How are Pyramidal Peaks formed
When three or more corries cut back into the same mountain they leave a pyramidal peak
Glacial landforms created by glacial deposition
Moraines.
Drumlins.
Erratics.
Crag and tail.
What are Moraines and how are they formed
A moraine is the type of landform that is created when a glacier deposits the material (till) that it has been transporting. It is made up of unsorted angular rocks. There are several types of moraine
Different types of moraine
Ground moraine. Terminal moraine. Medial moraine. Lateral moraine. Recessional moraine.
Ground moraine
It is dragged beneath a glacier and forms parts of the valley floor
Terminal moraine
It is found at the snout and marks the maximum advance of a glacier
Medial moraine
It is found in the centre of a glacier.
Lateral moraine
It is produced from frost shattering of the valley sides and is carried at the sides of the glacier.
Recessional moraine
It is formed at the snout of a glacier when the retreat of the glacier is halted for a period of time. They can be found between the snout of the glacier on the terminal moraine
Drumlins
Drumlins are formed of tail. They are elongated features that can reach a kilometre or more in length, 500 m or so in width and over 50 m in height. It is common to find several drumlins group together. A collection of drumlins is called a swarm
Erratics
An erratic is a boulder that is different to the bedrock upon which it is sitting. They have been transported and deposited by a glacier. Therefore erratics are useful indicators of patterns of former ice flow
Deposition
Deposition occurs when a rise in temperature causes ice to melt and the glacier is no longer able to carry as much material
