Hazards from Mass Movements 9.2

Question 1

REVISE MASS MOVEMENTS AS FIRST

Answer 1

You need the prior knowledge

Question 2

What are mudflows?

Answer 2

Fine grains mixed with water slowing down a channel.

Accumulates material down the slope

Question 3

What are Falls?

Answer 3

Occur on steep slopes with bare rock and exposed joints
Rocks detach and fall freely under gravity
Significantly contribute to the retreat of steep rock faces and providing debris for scree/talus slopes

Question 4

What are Slides?

Answer 4

When an entire mass of material moves alomg a slip plane, internal structure is maintained.
Water infiltrates through limestone and adds material on slope.
Water then lubricates the slope and slide occurs

Question 5

What conditions are needed for Slides?

Answer 5

Weak rocks, steep slope, active under-cutting or sudden change in water content

Question 6

What is a landslide?

Answer 6

When material moves downslope as a result of shear failure.
Downward force is more than resistance
Increase in water content reduces the strength and more mass is added

Question 7

What are avalanches?

Answer 7

Fast (40-200km/h) mass movements of ice and snow along a slip plane, often where the slope is steeper than 22°.
Often triggered by skiing, when new snow falls off old snow layer, or where lack of sun means snow does not stabilise on the slope

Question 8

Risk Perception of mass movements

Answer 8

Further distance from the site, less risk
Longer time between events leads to more paranoia
Governments and private land-owners should be well informed and take responsibility for informing the public. (e.g. Honk Kong case study AS)