Mechanisms of ice movement - Subglacial bed deformation Flashcards

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1
Q

What is subglacial bed deformation?

A

Subglacial bed deformation is a type of ice movement resulting from the deformation of soft sediment or weak rock beneath the glacier.

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2
Q

Subglacial bed deformation occurs in which type of glaciers?

A

Subglacial bed deformation occurs in warm based glaciers.

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3
Q

When does subglacial bed deformation take place?

A

Subglacial bed deformation occurs when a glacier moves over relatively weak or unconsolidated material such as glacial till.

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4
Q

What is deposited subglacial till made up of?

A

Deposited subglacial till is made up of poorly sorted sediments ranging from boulders to clay, and till sequences can be up to tens of meters thick.

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5
Q

What impact do finer sediments within the glacial till have on overlying ice and why?

A

The finer sediments within the till are not cohesive and the weight of the ice, together with a high pore water pressure inside the sediment, increased by glacial meltwater at the ice/bedrock interface, displaces the overlying ice.

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6
Q

What is the result of lower friction between the individual sediment grains?

A

Friction between individual sediment grains is reduced by the high pore water pressure resulting in the sediment deforming in response to the glaciers weight.

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7
Q

Locally, subglacial bed deformation can account for what percentage of the forward motion of glacier ice?

A

90%

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8
Q

In polythermal outlet glaciers in Iceland, subglacial bed deformation is responsible for the formation of glaciotectonic sequences. What does this mean?

A

Glaciotectonic refers to deformations in sediment and bedrock of the Earth’s crust as a consequence of glacier loading, dragging or pushing.

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