Sub-aerial Processes

Question 1

Physical weathering on coasts

Answer 1

• freeze-thaw
• salt crystallisation
• wetting + drying

Question 2

Freeze-thaw

Answer 2

• water entrees cracks in rocks + then the water freezes overnight during the winter
• as it freezes, water expands by 10% in volume which increases pressure on surrounding rocks
• this causes cracks to develop
• over time the cracks grow, weakening the cliff making it more vulnerable to other processes of erosion

Question 3

Salt crystallisation

Answer 3

• as seawater evaporates, salt is left behind
• sodium + calcium compounds
• salt crystals will grow over time, exerting pressure on the rock which forces the cracks to widen

Question 4

Wetting + drying

Answer 4

• rocks such as clay expand when wet + contract when drying
• the repeated cycle creates layers, causing the rocks + cliffs to break up

Question 5

Chemical weathering on coasts

Answer 5

• carbonation
• solution

Question 6

Carbonation

Answer 6

• rainwater absorbers CO2 from the air to create a weak carbonic acid
• the acid reacts with calcium carbonate in rocks to form calcium bicarbonate, which can then be easily dissolved
• acid rain reacts with limestone to form calcium bicarbonate = easily dissolved allowing erosion

Question 7

Solution

Answer 7

• weathering of calcium by acidic water
• tends to occur in rock pools due to presence of organisms secreting organic acids

Question 8

Biological weathering

Answer 8

• carried out by molluscs, sponges + sea urchins
• very important on low energy coasts
• birds such as puffins dig burrows into cliff = weakening them + making erosion more likely

Question 9

Mass movements on coastlines

Answer 9

• soil creep
• mudflows
• rockfall
• landslides

Question 10

Soil creep

Answer 10

• slowest but most continuous form of mass movement involving the movement of soil particles downhill
• particles rise + fall due to wetting + freezing = causing soil to move down slope
• forms shallow terracettes

Question 11

Mudflows

Answer 11

• an increase in water content of soil can reduce friction, leading to earth + mud to flow over underlying bedrock or slippery material such as clay
• water can get trapped within rock increasing pore water pressure, which forces rock particles apart + weakens the slope

Question 12

Rockfall

Answer 12

• occurs on sloped cliffs over 40° when exposed to physical weathering
• mostly occurs on vertical cliff faces + can be triggered by earthquakes
• leads to scree building up at the base of the slope

Question 13

Landslides

Answer 13

• occurs when a block of intact rock moves down the cliff face very quickly along a flat slope
• heavy rainfall leads to water between joints + bedding planes in cliffs (which are parallel to cliff face)
• this reduces friction + can lead to a landslide