Glaciers Flashcards
What is a firn?
rounded, well-bonded snow that is older than one year.
How is a glacier formed?
Glaciers begin to form when snow remains in the same area year-round, the process of the glacier forming takes a very long time- over 100 years.
Yearly, new layers of snow bury and compress old layers of snow, that were there previously. This compression causes the snow to crystallise, forming grains similar to the size of sugar grains.
Eventually the grains get larger, the air pockets in between them get smaller, causing the snow to compact and increase in density. After two winters, it turn into a firn. At this point it’s about half dense as water. Over time, larger ice crystals become so compressed that any air pockets between them are very tiny.
What is a glacier?
A glacier is a mass of ice that moves very slowly downhill. They are made up of fallen snow that, over many years, compresses into large, thickened ice masses.
What is plucking?
Plucking occurs when rocks and stones become frozen to the base or sides of the glacier and are plucked from the ground or rock face as the glacier moves. It leaves behind a jagged landscape.
What is abrasion?
Abrasion occurs when rocks and stones become embedded in the base and sides of the glacier. These are then rubbed against the bedrock (at the bottom of the glacier) and rock faces (at the sides of the glacier) as the glacier moves. This causes the wearing away of the landscape as the glacier behaves like sandpaper. It leaves behind smooth polished surfaces which may have scratches in them called striations. Striations are carved out by angular debris embedded in the base of the glacier.
What are the inputs and outputs of glaciers?
The main inputs to the glacial system are water, in the form of snow, and eroded sediments that are picked up by the moving ice.
Meltwater is the main output from the glacier, along with some evaporation.
In the summer and at lower altitudes, outputs will exceed inputs.
What are corries?
Corries, also known as cwms or cirques, are often the starting point of a glacier.
What are tarns?
When ice in a corrie melts, a circular lake is often formed at the bottom of the hollow. This is known as a tarn.
