Types of weathering

Question 1

types of mechanical weathering are (3)

Answer 1

• freeze thaw weathering
• salt crystallisation
• wetting and drying

Question 2

freeze thaw weathering is when

Answer 2

• water enters cracks in the rock face and freeze, expanding in doing so and so putting stress on the rock fissure
• the water then melts, and the rock relaxes
• this repeated over time means pieces of rock fall off, and the rock below expands with the release of pressure, so forms new cracks
• this makes the new layer of rock susceptible to further weathering

Question 3

salt crystallisation is when

Answer 3

salt from sea water forms crystals inside cracks when the water evaporates, building up pressure and expanding the cracks

Question 4

wetting and drying is when

Answer 4

some permeable rocks such as clay expand when they absorb water and retract when dry, so form cracks which make it vulnerable to freeze thaw weathering and salt crystallisation

Question 5

biological weatheirng is when

Answer 5

rock is broken down by plant or animal activity

Question 6

three examples of biological weathering are:

• (shellfish)
• (algae and fungi)
• (roots)

Answer 6

• the piddock shellfish has a shell which drills into soft chalk rock and so weakens its structure
• algae and fungi can break down minerals and create solution, so ‘dissolving’ the rock surface
• plant roots exploit cracks int he rock and grow, so expanding the crack and weakening the structure

Question 7

types of chemical weathering are (4)

Answer 7

• oxidation
• hydration
• hydrolysis
• carbonation

Question 8

• oxidation is when

- and the rocks most affcted are

Answer 8

• when rocks disintegrate as oxygen dissolved in sea water reacts with minerals to produce hydroxides and oxides
• ferrous rocks are especially affected (iron rich)

Question 9

hydration is when

Answer 9

when water is added to rock and the rock expands, forming cracks and then weakening the structure. permeable rocks such as limestone are most affected

Question 10

hydrolysis is when

Answer 10

when midly acidic water reacts with rock, it creates dissolved clays and salts, which degrades parent rock and weakens it

Question 11

carbonation is when

Answer 11

• when dissolved CO2 in rainwater forms weak carbonic acid (H2CO3).
• this reacts with rocks such as chalk or limestone to form bicarbonates which then dissolve easily in water, so are washed away.

Question 12

what product of fossil fuel combustion adds to carbonation

Answer 12

sulphur dioxide and nitrogen dioxide