Erosion

Question 1

How does attrition work?

Answer 1

Waves continually move rocks, pebbles and sand, especially in the surf zone. As the sediments move, projecting angular corners are knocked away.

Question 2

How does abrasion work?

Answer 2

Destructive waves pick up sand and pebbles and scrape/throw them against the rock, abrading it.

Question 3

How does corrosion work?

Answer 3

Water from waves may react with rock minerals and dissolve them. The minerals are carried away in the seawater.

Question 4

How does hydraulic action work?

Answer 4

A large destructive wave breaks on a cliff exerts 50kg/cm2 of pressure. Air may be compressed into cracks/joints in the rock. Sudden release of this pressure can shatter the rock.

Question 5

When does most erosion happen?

Answer 5

In winter when destructive waves are big and powerful.

Question 6

How does lithology influence erosion?

Answer 6

At a small scale, geological weaknesses are eroded more quickly.
Bands of more-resistant rock between weaker joints and cracks erode more slowly. The selective erosion of areas of weakness is called differential erosion.
At a medium/large scale, areas of resistant rock generally form cliffs and headlands, while weaker rocks form lowland areas with bays and inlets.

Question 7

Describe destructive waves.

Answer 7

13-15 per minute.
Stronger backwash than swash as the backwash of one wave interrupts the swash of the next.
Deep water.
Circular motion.
Removes sediment from the beach.
Approaches steep shingle beaches due to deep water.

Question 8

Describe constructive waves.

Answer 8

Nearshore depths are shallow and there are gently sloping sandy beaches.
Wave frequency is 6-8 per minute.
Swash is not interrupted by previous wave.
Elliptical motion (oval) giving it a strong forward motion.
Swash = stronger than backwash = deposition of sediment.

Question 9

What do waves result from?

Answer 9

Friction between the wind and sea surface.