Coastal Geography, Rocky Coasts

Question 1

What is the difference between depositional and erosional coasts?

Answer 1

Depositional coasts (beaches and estuarine systems) are developed through sediment accretion.

Contrarily, rocky coasts develop via erosion (erosional coasts)

Question 2

What are the three main characteristics of a rocky/erosional coast?

Answer 2

1. Very low sediment supply
2. Less responsive to short term change in wave and tidal energy
3. They are a product of long term wave and tide action, ranging from 10 to 10,000+ years)

Question 3

What are the three main characteristics of a rocky/erosional coast?

Answer 3

Cliff, stack, and shore platfrom

Question 4

Cliff

Answer 4

The archetypical erosional front of the coast

Question 5

Stack

Answer 5

Remnants of cliffs, representing the former outline of the coast

Question 6

Shore platform

Answer 6

The rock surface at mean tide level, including the foot of the cliff

Question 7

What are the two steps of cliff erosion and how do they operate?

Answer 7

1. Undercutting of cliff base which forms debris (often occurs in the form of mass failure)
2. Debris is subsequently removed by a variety of marine processes, forming a sheer cliff face

Question 8

How do shore platforms form?

Answer 8

An eroded rocky coast leaves behind a shore platform marking the mean tidal range

Question 9

What are the two main mechanisms acting on rocky coasts?

Answer 9

The mechanical action of waves, and weathering

Question 10

What are the four physical forces of wave quarrying?

Answer 10

Wave shock, hammer, compression, and abrasion

Question 11

Wave shock

Answer 11

Results from steep, high energy waves breaking against the coast

Question 12

Wave hammer

Answer 12

The repititive action of waves breaking and eroding the coast

Question 13

Wave compression

Answer 13

Air enters the cracks of rocks, becoming increasingly compressed until the rock breaks off

Question 14

Wave abrasion

Answer 14

Eroded material/sediment rubs against the coast, further eroding it

Question 15

What are the three types of weathering?

Answer 15

Physical, chemcial, and biological

Question 16

Water-layer weathering

Answer 16

A type of physical weathering whereby alternating periods of dampness and dryness cause the rocks to experience a constant rate of expansion and contraction, slowly eroding it over time

Question 17

Solution of calcareous rocks

Answer 17

A type of chemical weathering whereby sea water erodes the calcium carboate found in many sedimentary rocks

Question 18

Bio-erosion

Answer 18

A type of biological weathering that produces minor changes to a marine environment’s morphology. Bio-erosion is caused by marine organisms in the form of dissolving substances or burrowing within sediment

Question 19

What two characteristics of rock are important to the effect of the mechanical action of waves and weathering?

Answer 19

Bedding planes and permeability

Question 20

Bedding planes

Answer 20

Planes separating strata of sediment, thus indicating times of sediment change and/or a change in the depositing medium

Question 21

Permeability

Answer 21

Strata have different levels of permeability which influences how easily waves/water can erode the substance

Question 22

What are the two main types of coastlines

Answer 22

Concordant and discordant coastlines

Question 23

Concordant coastline

Answer 23

A unfiorm coastline with strata composed of similar material

Question 24

Discordant coastline

Answer 24

A non-uniform, splintered coastline with strata compsoed of disimilar material

Question 25

How does tide infleunce shore platform growth

Answer 25

The smaller the tidal range the greater the duration of wave quarrying.

Smaller tidal range = Faster cliff retreat

Question 26

What are the two factors of variable tidal influence?

Answer 26

Tidal elevation and tidal duration

Question 27

Tidal elevation

Answer 27

The position of wave quarrying on a shore platform

Question 28

Tidal duration

Answer 28

The distribution of wave energy on a shore platform

Question 29

What is the changing rate of cliff retreat?

Answer 29

Initally cliff retreat is modest, eventually speeding up only to slow down again

Question 30

What causes the changing rate of cliff retreat, otherwise known as the neagtive feedback relationship?

Answer 30

Acceleration is due to increased abrasion from more sediment.

Deceleration is due to the removal of sediment from the foreshore. This sediment is deposited offshore, causing waves to break earlier and approach the shore with less energy.

Question 31

What is the difference in wave energy between broken and breaking waves?

Answer 31

Broken waves spread their energy out over a greater area while breaking waves exert more force over a smaller area

Question 32

Why doesn’t a cliff in deep water experience much erosion?

Answer 32

Since waves don’t encounter the seafloor in deep water, they don’t shaol. This causes the wave energy to be reflected with little erosion occuring on the cliff face