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Flashcards in Mass movement Deck (16):

What causes mudflows?

Heavy rain casuses large amounts of material to move downhill.


What happens when the material moves down hill?

The soil then becomes saturated.


What happens if excess water cannot percolate deeper into the ground surface layers?

The layers become very fluid and flow down hill.


What is the nature of the flow dependent on?

The level of saturation, the type of sediment and slope angle.


Rockfalls occur from what?

Cliffs undercut by the sea.


Name another way rockfalls can occur ?

On slopes affected by mechanical weathering like frost action.


Where do landslides occur?

They occur on cliffs made from softer rocks or deposited material.


What then causes the landslides?

The material or softer rocks then slip as a result of failure when lubricate.usually by heavy rainfall.


What causes rotational slip or slumping?

Where softer material overlies the more resistant materials.
Cliffs become more subject to slumping.


The more lubrication, what could happen?

Whole sections of the cliff may move downhill. With a slide plane that is concave producing a rotational movement.


What example is where rotational slip or slumping may occur?

Coastal area East Yorkshire and north Norfolk


Soil creep occurs when?

When there is a very slow almost imperceptible, but continuous movement of individual soil particles downslope.


What are the causes of soil creep?

Soil moisture, range of weathering and other processes.


Where is mass movement most common ?

Coastlines that are steep


What is runoff?

Important process that operates on coastlines.
It may take the form of a steam emerging in a bay, taking with it large quantities of load during times of flood, or it may be a stream cascading over a cliff excavating a V-shaped groove as it does so.


What can surface run off also be ?

Water that flows off the surface to reach the coastline, the presence of which will also assist many of the mass movement processes above.