Sub-aerial Processes: Weathering

Question 1

What is weathering?

Answer 1

• the breakdown of rocks over time

Question 2

What are the 3 types of weathering?

Answer 2

• mechanical (physical) weathering
• chemical weathering
• biological weathering

Question 3

What is mechanical (physical) weathering?

Answer 3

• breakdown of rocks due to exertion of physical forces

Question 4

What are the diff. processes of mechanical weathering in coastal envi.?

Answer 4

• freeze-thaw
• salt crystallisation
• wetting + drying

Question 5

What is freeze-thaw?

Answer 5

• when water in cracks of rocks freezes at 0°C + repeatedly expands as it cools by 10%
  
  • puts pressure on surrounding rocks causing cracks to debelop: grow over time, weakening cliff making it more vulnerable to other processes of erosion

Question 6

What is salt crystallisation?

Answer 6

• when salts left behind in cracks, by evaporation of seawater, grows over time
  
  • exerts pressure on surrounding rocks, forcing cracks to widen + eventually break off or disintegrate
• salt can also corrode rocks containing Fe due to chemical reactions

Question 7

What is wetting + drying?

Answer 7

• when rocks (e.g. clay) repeatedly expand when wet + contract again when drying
  
  • causing rocks + cliffs to break up

Question 8

What is chemical weathering?

Answer 8

• breakdown of rocks caused by chemical reactions

Question 9

What are the diff. processes of chemical weathering in coastal envi.?

Answer 9

• carbonation
• oxidation
• solution

Question 10

What is carbonation?

Answer 10

• when [1] rainwater w dissolved CO2 from the air forms a weak carbonic acid which [2] reacts w CaCO3 in rocks to form calcium bicarbonate
  
  • soluble + is washed away allowing erosion

[1] H2O + CO2 —> H2CO3
[2] H2CO3 + CaCO3 —> Ca(HCO3)2

Question 11

What is oxidation?

Answer 11

• when minerals are exposed to air through cracks + fissures, they become oxidised so will inc. its vol, causing rocks to crumble
  
  • e.g. iron minerals in rocks becoming iron oxide, turning rocks rusty orange after being exposed to air

Question 12

What is solution?

Answer 12

• when rock minerals (e.g. rock salt) are dissolved

Question 13

What is biological weathering?

Answer 13

• breakdown of rocks by organic activity

Question 14

What are the diff. processes of biological weathering in coastal envi.?

Answer 14

• root action
• birds
• rock boring
• seaweed acids
• decaying vegetation

Question 15

What is root action?

Answer 15

• when roots of plants grow into cracks of rocks + exerts pressure onto surrounding rocks causing rocks to eventually split

Question 16

How do birds act as a biological weathering process?

Answer 16

• some birds (e.g. puffins) dig burrows into cliffs weakening them + making erosion more likely

Question 17

What is rock boring?

Answer 17

• when species of clams secrete chemicals that dissolve rocks + piddocks may burrow into the rock face

Question 18

How do seaweed acids act as a biological weathering process?

Answer 18

• some seaweed species contain pockets of sulphuric acid, which if hit against a rock or cliff face, the acid dissolves some of the rocks minerals (e.g. kelp)

Question 19

How does decaying vegetation act as a biological weathering process?

Answer 19

• water flowing through decaying veg. + then over coastal areas, will be acidic, thus causing chemical weathering