Weathering And Erosion

Question 1

Mechanical:
Process - Freeze-thaw

Give an explanations and type of rocks vulnerable to Freeze-thaw:

Answer 1

Explanation:
Water expands by 9% in volume when freezing, exerting a force within cracks and fissures; repeated cycles force cracks open and loosen rocks

Vulnerable rocks: any rocks with cracks and fissures, especially high up cliffs away from salt spray. Freezing is relatively uncommon on UK coasts, especially in the South, and salt spray can reduce its effect even further.

Question 2

Mechanical:
Process - Salt crystallisation

Give an explanations and type of rocks vulnerable to Salt crystallisation

Answer 2

Explanation: the growth of salt crystals in cracks and pore spaces can exert a breaking force, although less than for freeze thaw.

Vulnerable rocks: Any rocks with cracks and fissures, especially high up cliffs away from salt spray. Freezing is relatively uncommon on UK coasts, especially in the South, and salt spray can reduce its effect even further.

Question 3

Chemical:
Process - Carbonation

Give an explanations and type of rocks vulnerable to Carbonation:

Answer 3

Explanation: The slow dissolution of limestone due to rainfall (weak carbonic acid, pH 5.6) producing calcium bicarbonate in solution

Vulnerable rocks:
Limestone and other carbonate rocks

Question 4

Chemical
Process - Hydrolysis

Give an explanations and type of rocks vulnerable to Hydrolysis

Answer 4

Explanation: the breakdown of minerals to form new clay minerals, plus materials in solution, due to the effect of water and dissolved CO2.

Vulnerable rocks: Igneous and metamorphic rocks containing feldspar and other silicate minerals

Question 5

Chemical
Process - Oxidation

Give an explanations and type of rocks vulnerable to Oxidation

Answer 5

Explanation: the addition of oxygen to minerals, especially iron compounds, which produces iron oxides and increases volume contributing to mechanical breakdown.

Vulnerable rocks: Sandstones, siltstones, and shales often contain iron compounds that can be oxidised.

Question 6

Biological
Process - Plant roots

Give an explanations and type of rocks vulnerable to Plant roots

Answer 6

Explanation: Trees and plant roots growing in cracks and fissures forcing rocks apart

Vulnerable rocks: an important process on vegetated cliff tops that can contribute to rockfalls

Question 7

Biological
Process - Rock Boring

Give an explanations and type of rocks vulnerable to Rock Boring

Answer 7

Explanation: Many species of clams and mollusks bore into rock and may also secrete chemicals that dissolve rocks

Vulnerable rocks: Sedimentary rocks, especially carbonate rocks (limestone) located in the inter-tidal range