Glaciation Flashcards
When was the last ice age in Europe and the British isles?
It ended about 18,000 years ago, ice sheets several metres thick spread down the north as the climate eroded and glaciers filled the eroded valleys. Today the ice sheets have retreated
What is a glacial period?
An interval in time within an ice age that is marked by colder temperatures and glacier advances.
What is an interglacial period?
During an ice age there are periods of colder and warmer average global temperatures. The warmer periods are called interglacial periods because they separate the colder periods during the ice age.
Talk about the Mer De Glace glacier
It is found in the Alps, NE or Mont Blanc, it’s 7km long, 1200m wide and 200m thick. It is the longest and largest glacier in France. It’s name means SEA OF ICE. It moves at a speed of 70m a year.
It’s fed by snow flakes at an altitude of 4000m
What is the glacier system?
Inputs; snow accumulates
Stores;over time snow turns to ice
Transfers;glacier moves downslope under the pull of gravity
Outputs;meltwater and some evaporation
What is accumulation?
In the winter, inputs usually exceed outputs near to the head of a glacier.
What is ablation?
In the summer and at lower altitudes outputs will exceed inputs.
What is plucking?
The water at the bottom of the glacier freezes onto rock on the valley base. As the glacier moves, the rock is pulled away from the valley base. Plucking mainly occurs when the rock is well jointed.
What is a cirque/Corrie?
Deep bowl shaped landform created by the glacier.
What is abrasion?
The moraine frozen into the glacier scours the valley sides and floor, this has a sandpapering effect similar to corrosion by a river but on a larger scale
What is the snout?
End of the glacier. Pushes huge amounts of material in front, moraine.
What are crevasses?
Cracks in the ice, they can be metres across and perhaps 5-10m deep. They form when the ice is shredded as it flows down a steep slope. Extremely dangerous because they open and close as glaciers move. They may be hidden under fresh snow
What is frost shattering?
Water that enters cracks in rocks freezes and when it does, it expands. Repeated freeze and thaw means cracks in the rock and expand until the rock is fractured. This leads to material falling off the sides of the mountain slopes on to glacier.
What are glacial striation marks?
Striation marks are marks left by glaciers as they travel across an area. These marks can tell us the direction of movement of the glacier.
How do you form a U shaped valley?
Formed by glacier in mountain valleys and have a characteristic U shape, with steep straight sides and a flat bottom. They are formed when a glacier travels across and down a slope, carving a valley. When the ice retreats or thaws the valley is often covered with small boulders that were transported within the ice as glacier till.
