Mass movement/weathering processes

Question 1

Boring Molluscs (Biological weathering)

Answer 1

Many marine molluscs live on (carbonate) rocks scrapping away at the rock surface to make a home, e.g. Paddock, which has a shell with serrated cutting edges.

Question 2

Frost-shattering

Answer 2

Also known as freeze-thaw weathering. It is a process where water becomes trapped in a crack or joint in the rock. If the air temperature drops below freezing, the water will freeze and expand by 9-10 per cent putting pressure on the rock. The ice will melt when the temperature rises above freezing, weakening the rock and eventually shattering. Fragments may be deposited as scree at the foot of a slope.

Question 3

Mass Movement

Answer 3

The movement of material down a slope as a result of gravity. E.g. rotational slump, mudflow, earthflow, debris avalanche or rockfall.

Question 4

Mudflows

Answer 4

A type of mass movement due to an increase in the amount of precipitation reducing friction, causing saturated earth and mud to flow over underlying impermeable bedrock. Occurs on steep slopes over 10 degrees.

Question 5

Oxidation

Answer 5

The reaction between oxygen (in air/water) and compounds in rocks that result in the removal of one or more electrons, causing the structure to be less rigid and increasingly unstable (crumble more easily).

Question 6

Sub-aerial processes

Answer 6

Name for the processes of weathering and mass movement.

Question 7

Salt Crystallisation

Answer 7

Salt (sodium and magnesium) crystals grow in the joints and exert pressure and force the rocks apart.

Question 8

Talus (Scree)

Answer 8

The pile of rocks that accumulates at the base of a cliff, chute, or slope, as a result of mass movement.

Question 9

Weathering

Answer 9

Breakdown of rock in one place (in situ) by the weather. There is no change in the chemical composition of the broken-down material. It can be divided into mechanical/physical, biological, and chemical.

Question 10

Rotational slumping

Answer 10

A form of mass movement in which rainwater infiltrates the cliff through unconsolidated, porous material (e.g. boulder clay), creating a slip plane, with rotation about an axis parallel to the slope. The weight of the saturated clay causes the material to slump along the slip plane. Rotational movement causes the original surface of the block to become less steep, and the top of the slump is rotated backward.