G - Glacial movement Flashcards Preview

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Flashcards in G - Glacial movement Deck (11):

What are the types of ice movement?

Internal deformation, rotational flow, compressional, extensional and basal sliding


What is the definition of: basal sliding

Meltwater underneath the glacier allows the glacier to slide over the ground


What is the definition of: Internal deformation/flow

Where the ice bends and warps to flow downhill like a liquid


What is the definition of: Extensional flow

When the layers of ice slip downwards after tension causes the ice to fracture into thick layers


What is the definition of: Conpressional flow

When layers slip forwards after high pressure causes the ice to fracture into layers


What is the definition of: Rotational flow

What glaciers move in an arc shape when they're in a hollow (by basal sliding)


Explain basal sliding

Temperate glaciers move mainly through through basal slippage
If the glacier moves - this can raise the temperature of the base through pressure and friction - the basal ice can then melt, and this water helps to allow the ice to slop more easily over its bed
→ They can move 2-3m a day


Explain internal deformation/flow

This is the main way in which cold based (polar) glaciers move
These glaciers are stuck to the bed and can therefore only move 1-2cm a day
→The ice crystals orientate themselvrs in the direction of ice movement - this allows ice crystals to slide past one another
→Where ice movement is fast enough crevasses may develop


Explain Extensional

At the head of a glacier the valley is steep, so there's a strong gravitational force pulling the ice downwards. This makes the ice move quickly - when ice moved quickly there's more tension which causes the ice to fracture into thick layers - these layers slip downwards which is extensional flow


Explain Compression flow

Lower down the glacier is moving more slowly because the valley is less steep
The faster ice from the head of the glacier pushes down on the slower ice and compresses it. The high pressure causes the ice to fracture into layers and the layers slip forwards - this is compressional flow


Explain rotational flow

This occurs within the corrie (cirque), the ice moving downhill can pivot about a point - producing a rotational movement
→ this combines with increased pressure within the rock hollow, leads to greater erosion and over deepening of the corrie floor