LO 1.3 - Chemical factors in soil formation

Question 1

What is chemical weathering: acids?

Answer 1

Carbon dioxide dissolves in rainwater to form weak carbonic acid which breaks down rock. If air contains eg sulphur this will further acidify the rain and cause chemical weathering.

This chemical weathering happens below ground too (limestone caves).

Question 2

What is chemical weathering: dissolution?

Answer 2

Some minerals dissolve in water – eg sodium chloride and potassium chloride – once these dissolve they can be washed away in solution.

Calcite in limestone dissolves easily leaving this characteristic karst landscape like the Burren.

Question 3

What is chemical weathering: oxidation ?

Answer 3

• Oxidation (or ‘rusting’) of rocks can take place in the presence of oxygen.
• This process weakens the rock (and can also change its colour).

Question 4

Consider this

Chemical weathering: plants, lichens, fungi.

Answer 4

• They produce carbon dioxide that makes water slightly acidic.
• Lichens secrete acid substances that dissolve rocks, releasing the minerals.