bays and headlands - erosion

Question 1

how do bays and headlands form?

Answer 1

form adjacent to each other, along discordant coasts with alternating bands of weak and strong lithology

Question 2

what do the weaker and resistant bands result in?

Answer 2

the weaker bands of rock erode faster to form bays
the resistant bands remain sticking out to sea as headlands
- the width of the bay is determined by the width of the band of weak rock

Question 3

what does wave refraction result in?

Answer 3

wave refraction slows the waves in the shallow water off the headlands and moves faster into the bays as the water is deeper for longer

Question 4

what do the waves refract around?

Answer 4

the waves refract around the headlands and the orthogonals converge - concentrating the energy
- in the bats the orthogonals diverge, dissipating energy and allowing deposition (beaches form)

Question 5

what does bay depth depend on?

Answer 5

bay depth depend on differential rates of erosion between more resistant + weaker rocks

Question 6

what/ forms in discordant coastline?

Answer 6

if rock outcrops lie perpendicular to coastline weaker rocks are eroded more rapidly to form bays while more resistant rocks remain between bays as headlands

Question 7

what is concordant coastline?
what happens if more resistant rock lies on seaward side?

Answer 7

rocks lying parallel to the coastline
- if most resistant rock lies on the seaward side, it protects weaker rocks inland from erosion
- but small bays or coves can be eroded at points of weakness such as fault lines

Question 8

what happens when wave refraction approaches irregularly shaped coastline?

Answer 8

when waves approach irregularly shaped coastline wave refraction takes place and develops an increasing configuration parallel to coast
- at same time, part of wave crest in the deeper water approaching the bay moves faster as it’s not slowed by friction
- so wave bends/refracts around headland and orthogonals converge (wave energy + erosion focused on headland)

Question 9

how do beaches form after deposition?

Answer 9

as wave breaks on the sides of headland at and angle there is longshore movement of eroded material into the bays adding to the build up of beach sediment