Weathering and Mass Movement

Question 1

What is weathering?

Answer 1

Weathering is a process by which the specific surface area of a rock is increased.

Question 2

What is the effect of weathering on quartz?

Answer 2

Quartz is very resistant to all types of weathering, whereas other rocks just decay into clays.

Question 3

What are the different types of physical weathering?

Answer 3

• Mechanical unloading
• Mechanical loading
• Freezing
• Wetting and drying
• Crystallisation

Question 4

How does mechanical unloading cause weathering?

Answer 4

Allows fissures to open up causing materials to expand vertically, resulting in horizontal cracks appearing in the bedding plane.

Question 5

How does mechanical loading cause weathering?

Answer 5

Impact by rain, sand and dust in the air, or sand, gravel and boulders in the water results in material breaking away from the surface of a rock.

Question 6

How does freezing cause weathering?

Answer 6

When water freezes, it expands applying pressure on cracks causing them to open up and disintegrate the rock.

Question 7

How does wetting and drying cause weathering?

Answer 7

Wetting and drying causes materials to expand and contract giving a similar effect to that of freezing, just not as powerful.

Question 8

How does crystallisation cause weathering?

Answer 8

Crystallisation has a similar effect to that of freezing.

Question 9

What are the different types of chemical weathering?

Answer 9

• Solution
• Carbonation
• Oxidation
• Hydrolysis

Question 10

How does solution cause weathering?

Answer 10

This is when rock is dissolved in water (especially with salt).

Question 11

How does carbonation cause weathering?

Answer 11

Slightly acidic rainwater containing dissolved carbon dioxide leads to the solution of a rock.

Question 12

How does oxidation cause weathering?

Answer 12

• Rock reacts with oxygen causing them to break down.
• This causes clay to turn from blue/grey to brown/red.

Question 13

How does hydrolysis cause weathering?

Answer 13

Hydrolysis is an irreversible reaction with water, causing one rock to decompose into another.

Question 14

What is the difference between chemical and physical weathering?

Answer 14

• Chemical weathering processes generally happen quicker and at higher temperatures.
• However, all weathering processes are helped by high rainfall.

Question 15

Which factors affect mass movement?

Answer 15

• Nature of material
• Water content
• Slope steepness

Question 16

How does water content affect mass movement?

Answer 16

• A little water allows a slope to stand very steeply as the water forces are significantly larger than the weight of the grains.
• If the slope dries out or becomes saturated, the water forces disappear as there is no longer any tension between the water and the air, and so the slop cannot stand as steeply.

Question 17

What factors affect landslides?

Answer 17

• The more brittle the material, the faster it moves.
• If high pressure water/air is mixed in, then movement can be very fast.

Question 18

What are the features of a rockslide?

Answer 18

When everything comes to a halt, the material breaks up and so can often turn into a flow.

Question 19

What is a rock avalanche?

Answer 19

An avalanche of rocks which is triggered by an earthquake.

Question 20

What feature is left behind after slumping?

Answer 20

A scar.

Question 21

What is soil creep?

Answer 21

1. When surface layers of the ground expand they move directly outwards.
2. They then contract, moving vertically downward, causing particles to move in a zig-zag motion down hill.

• The expansion and contraction can be caused by changes in moisture content or freezing and thawing.