2.6a

Question 1

Define subaerial processes

Answer 1

Subaerial Processes - The combination of mass movement and weathering that affects the
coastal land above sea.

Question 2

Define weathering

Answer 2

Weathering is the breakdown of rock in situ at or near the surface of the Earth

Question 3

State three types of weathering

Answer 3

Physical (mechanical), biological and chemical

Question 4

State two types of physical weathering

Answer 4

Frost shattering (freeze-thaw) weathering and salt crystallisation

Question 5

Describe frost shattering (freeze thaw) weathering

Answer 5

• Temperature has to change daily between above and below 0dc – expansion and contraction of water
• In FT, water seeps into joints / cracks / freezes and expands by 9%, exerting pressure and forcing the rock apart
• Rock is left angular, the cliff face would be jagged, and the material would accumulate at the bottom as a scree slope.

Question 6

Describe salt crystallisation weathering

Answer 6

• Waves break and splash water against the cliff during high tide
• The water evaporate, leaving sodium and magnesium salt compounds behind
• Often they’re in cracks and joint – and then the salt crystals grow, exert pressure, and force the rock apart. Sometimes this might happen within the porous rock itself.

Question 7

Effects of salt crystallisation?

Answer 7

Angular rock fragments are loosened and fall to create a scree slope at the base of the cliff; rock faces crumble

Question 8

State three methods of chemical weathering

Answer 8

Oxidation, carbonation, hydrolysis,

Question 9

Describe oxidation

Answer 9

Chemical reaction, with the iron-minerals in the rock, causing chemical breakdown of minerals. Leaves a red-orange rusty colour on the rock. The rock crumbles away – i.e. erosion is much easier.

Question 10

Describe carbonation weathering

Answer 10

• slow dissolution of limestone due to rainfall, (weak carbonic acid) causing a reaction with calcium carbonate in the rock to form calcium bicarbonate)
• calcium bicarbonate s easily dissolved allowing erosion

Question 11

Describe hydrolysis

Answer 11

• minerals breakdown to form new clay minerals, plus material in solution, because of water / dissolved CO2
• Rocks vulnerable to it are: igneous and metamorphic rocks containing feldspar and other silicate minerals
• This attacks the feldspar (pinky) minerals in granite

Question 12

Describe wetting and drying (mechanical)

Answer 12

Wetting and Drying
Rocks containing clay minerals, such as clays and shales
At high tide minerals on the rock surface are soaked with sea water and expand in volume.
At low tide, minerals dry and shrink.
Repeated cycles of expansion and contraction eventually cause the rock to fragment and crumbl

Question 13

State two biological methods of weathering

Answer 13

boring molluscs and seaweed acid

Question 14

Describe sea weed acid

Answer 14

E.g. kelp contains sulphuric acid, so if cells in kelp break, the acid dissolves the rock away
The rock minerals aren’t bonded together, so the rock crumbles.

Question 15

Describe boring molluscs

Answer 15

• Live on the rocks, scraping away to get food / boring a hole in the rock – e.g. a paddock has a shell with serrated cutting edges
• Holes bored into the rock, becoming weak points for weathering to act.

Question 16

Where does weathering mainly happen

Answer 16

• Weathering attacks the backshore and foreshore parts of the littoral zone.
• Weathering creates rock fragments that form sediment.
• It’s most active in the source zone of the sediment cell

Question 17

What is weathering important to

Answer 17

Sediment production and rate of recession