Mass Movement

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Why is mass movement common?
Because of the prevailing steep and therefore unstable slopes.
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When does mass movement more commonly occur? Why is this?
Winter. The more powerful waves undercut the cliff base.
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What is mass movement?
Material moving downslope due to the pull of gravity.
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Where can mass movement happen?
Almost anywhere.
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What is mass movement commonly associated with? What is an effect of this?
Other events eg. heavy rainfall and earthquakes. Mass movement is under reported.
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What is another name for a catastrophic mass movement?
Slope failure.
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What is another name for a slow and steady mass movement?
Creep.
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What increases the rate of mass movement?
Erosive agents, especially water.
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What are the four types of rapid mass movement?
Rock fall, rock slides, rock toppling, rotational slides and slumps.
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What is rock fall?
When blocks of rock, dislodged by weathering, fall to the cliff foot.
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Name an example of where rock fall happens.
Svalbard (a high latitude periglacial region). Here, rock blocks are loosened by freeze-thaw action.
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What are rock slides?
When blocks of rock slide down the cliff face, especially where rocks are dipping steeply towards the sea.
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Name an example of where rock slides happen.
The limestone cliffs of Tenby and Gower in South Wales.
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What is rock toppling?
Where blocks or even columns of rock, weakened by weathering, fall seawards.
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Name an example of where rock toppling happens.
Giants causeway in County Antrim in Northern Ireland.
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What is a rotational slide?
Where sections of the cliff give way along a well-defined concave slip surface. The fallen material stays as an inidentifiable mass off the shore because it is often composed of cohesive clays or boulder clay, it may take longer to be eroded.
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Where do slumps occur?
Where permeable rock overlays impermeable rock. eg. Christchurch and Barton on Sea (South of England).
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Where else are they common?
Unconsolidated rock eg. the sandy boulder clay deposits of North Norfolk and Holderness (both in eastern England).
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When are the sub-aerial processes most active?
After heavy rainfall.
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What does this lead to?
Saturation and subsequent lubrication.
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What is reached?
A critical threshold.
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What does this trigger?
Mass movement and slope failure, mudflows.
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What are the two types of slow mass movement?
Creep and solifluction.
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What is creep?
The extremely slow (imperceptible) downslope movement of regolith (the loose material including soil above the bedrock).
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What is solifluction?
The slow downward movement of regolith, saturated by the melting of the active layer above the permafrost.
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When did many parts of the UK probably experience solifluction?
The last ice age.
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Card 2

Front

When does mass movement more commonly occur? Why is this?

Back

Winter. The more powerful waves undercut the cliff base.

Card 3

Front

What is mass movement?

Back

Preview of the front of card 3

Card 4

Front

Where can mass movement happen?

Back

Preview of the front of card 4

Card 5

Front

What is mass movement commonly associated with? What is an effect of this?

Back

Preview of the front of card 5
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