wave erosion processes (2B.4B)

Question 1

the four processes

Answer 1

hydraulic action
abrasion
attrition
corrosion

Question 2

how are the processes influenced by wave type, size and lithology?

Answer 2

• they are most effective during high energy storm events with large destructive waves.
  ! however ! even coastlines composed of soft, unconsolidated sediment (e.g. boulder clay of Holderness Coast in Yorkshire), experience little erosion under normal conditions.
• most erosion (in the UK) occurs in the winter, in high energy storms.
• erosion rate= faster when the wind is blowing directly onshore
• erosion rate= faster when the tide is high (bringing deeper water closer to the cliff so less energy is lost to friction before impact)

Question 3

hydraulic action

Answer 3

force of water itself breaks into/ up a rock
- it can occur through the sheer force of the water on less resistant rocks
OR
- through the compression of air into cracks/ faults into more resistant cliff faces causing more micro fractures and expanding the main crack. the pressure forces the crack open, meaning more air is trapped and greater force is experienced in the next cycle of compression and dislodges blocks of rock from the cliff face.

Question 4

abrasion

Answer 4

where a wave picks up sediment and throws these load items against a rock. the repeated impact chips away at the rock face until small fragments break away.

• high-energy destructive waves with a large wave height hurl load items with greater force, resulting in faster rates of erosion by abrasion.
• soft sedimentary rock such as chalk, mudstones, and clays, and unconsolidated material are most effected.

Question 5

attrition

Answer 5

material transported by a wave is eroded through collision with other load items.
it breaks down sediment into smaller sized particles, and the repeated collision blunts any of the particles’ sharp edges, making the sediment increasingly rounded.

• occurs in the foreshore and nearshore zones, where sediment is moved by swash and backwash.
• affects sedimentary rocks the quickest but even harder rocks, such as quartz and granite form larger rounded shingle pebbles.

Question 6

corrosion

Answer 6

where water in waves dissolves rock minerals. these minerals are immediately carried away by the wave in solution. they are also vulnerable to erosion by rainwater and sea spray.

• cliffs formed from alkaline/ carbonate rock (eg chalk/ limestone) are most vulnerable and can be easily eroded by the weak acid
• constructive waves have biggest impact as force is not relevant, and the spilling wave increases the time for the chemical reaction to occur. they are slow with a long wavelength (longer the better) it prolonging the contact of rock with the water.