Crowded Coasts 2.3.2

Question 1

What are the key characteristics of constructive waves?

Answer 1

Low height, long wavelength, strong swash, weak backwash, low frequency (6–9/min), deposit sediment

Question 2

What are the key characteristics of destructive waves?

Answer 2

High height, short wavelength, weak swash, strong backwash, high frequency (11–16/min), erode beaches.

Question 3

How does wave frequency influence coastal processes?

Answer 3

Higher frequency waves (destructive) increase erosion; lower frequency waves (constructive) build beaches.

Question 4

What type of wave is more common in summer, and how does it shape the beach?

Answer 4

Constructive waves dominate, leading to wider, gently sloped beaches.

Question 5

How do destructive waves alter the beach profile in winter?

Answer 5

Remove sediment, creating narrower, steeper beach profiles.

Question 6

Define swash and backwash.

Answer 6

Swash: movement of water up the beach. Backwash: movement of water returning to the sea.

Question 7

What is the difference between a swash-aligned and a drift-aligned coast?

Answer 7

Swash-aligned: waves hit parallel, little longshore drift. Drift-aligned: waves hit at an angle, causing longshore drift.

Question 8

How does the angle of wave approach influence sediment transport along the coast?

Answer 8

The steeper the angle, the more effective longshore drift is at transporting sediment.

Question 9

What kind of beach forms under low-energy wave conditions?

Answer 9

Sandy, gently sloping beaches due to deposition.

Question 10

How do seasonal changes influence beach sediment profiles?

Answer 10

Summer: deposition dominates (wider beach). Winter: erosion dominates (narrower beach).

Question 11

Name the six main marine erosion processes.

Answer 11

Hydraulic action, abrasion, attrition, corrosion (solution), corrasion, wave quarrying

Question 12

What is hydraulic action and how does it affect rock structures?

Answer 12

Waves force air into cracks, increasing pressure and causing rock to fracture.

Question 13

Describe abrasion and how it contributes to cliff erosion.

Answer 13

Sediment in waves grinds against the cliff face, wearing it down.

Question 14

How does attrition differ from corrasion?

Answer 14

Attrition is rocks hitting each other and breaking down; corrasion is rocks hurled at cliffs by waves.

Question 15

Which rock type erodes the fastest: granite, limestone, or basalt?

Answer 15

Limestone (sedimentary)

Question 16

Why are sedimentary rocks more prone to erosion?

Answer 16

They are clastic with many faults and joints, making them weaker.

Question 17

What erosion rate would you expect for metamorphic rocks?

Answer 17

0.1–0.3 cm/year — slower due to crystalline structure.

Question 18

How do cracks and faults influence the erosion of a cliff face?

Answer 18

They allow water and pressure to enter, accelerating erosion processes like hydraulic action.

Question 19

What is a composite cliff and how is it formed?

Answer 19

A cliff made of multiple rock types with different resistances, creating a layered profile.

Question 20

How does the dip of rock strata influence cliff stability?

Answer 20

Seaward dip: unstable cliff; landward dip: more stable. Horizontal dip forms steep cliffs.

Question 21

Explain the formation of a wave-cut notch.

Answer 21

Erosion at the cliff base creates a notch between high and low tide.

Question 22

What is a wave-cut platform and how is it created?

Answer 22

As the notch deepens, the cliff collapses, leaving a flat platform.

Question 23

Describe the sequence of landforms formed from cave to stump.

Answer 23

Fault → cave → arch → stack → stump.

Question 24

What physical and marine processes contribute to the formation of blowholes?

Answer 24

Marine erosion forms a cave; weathering creates a pothole above. When they meet, a blowhole forms.

Question 25

How do headlands and bays form on a discordant coastline?

Answer 25

Softer rock erodes into bays, while resistant rock forms headlands.

Question 26

What role does wave refraction play in coastal landform development?

Answer 26

Concentrates energy on headlands (erosion) and disperses it in bays (deposition).

Question 27

How does differential erosion create complex cliff profiles?

Answer 27

Different layers erode at different rates, forming overhangs, notches, and varied slopes.

Question 28

Why do some headlands erode faster than others?

Answer 28

Headlands with more joints, faults, or weaker rock erode more rapidly.

Question 29

What are the three types of weathering affecting coasts?

Answer 29

Mechanical (physical), chemical, biological.

Question 30

Describe freeze-thaw weathering and its impact on cliff faces.

Answer 30

Water enters cracks, freezes, expands, and forces rock apart.

Question 31

What is salt crystallisation and how does it contribute to rock weakening?

Answer 31

Salt left after seawater evaporates forms crystals that widen cracks.

Question 32

How do plant roots contribute to biological weathering?

Answer 32

Roots grow into cracks and exert pressure, splitting the rock.

Question 33

What is the difference between a slide and a flow in mass movement?

Answer 33

Slide: material moves as a block. Flow: material mixes and moves more fluidly.

Question 34

What conditions favour the occurrence of slumping?

Answer 34

Saturated soft rock (e.g. clay), gentle dip, and lack of vegetation.

Question 35

Define solifluction and where it commonly occurs.

Answer 35

In tundra areas; thawed top layers flow over frozen ground in summer.

Question 36

How does rainfall influence sub-aerial processes?

Answer 36

Increases saturation, leading to slumping and enhances weathering.

Question 37

Describe how longshore drift works.

Answer 37

Waves hit the beach at an angle, swash moves sediment up, backwash pulls it straight down, creating zig-zag motion.

Question 38

What is the difference between traction and saltation?

Answer 38

Traction: large particles roll on the seabed. Saltation: smaller particles bounce along.

Question 39

What conditions cause a wave to deposit its sediment?

Answer 39

Low energy conditions (e.g. shallow water, reduced wind), sediment becomes too heavy to carry.

Question 40

How does flocculation influence deposition in coastal areas?

Answer 40

Clay particles clump together due to chemical attraction and sink.

Question 41

Describe how a spit forms and how it develops a recurved end.

Answer 41

Longshore drift moves sediment into open water; wind direction changes, curving the end.

Question 42

What is a tombolo, and how is it formed?

Answer 42

A depositional bar connecting mainland to an island, formed by wave refraction and sediment deposition.

Question 43

Explain the difference between bars and cuspate forelands.

Answer 43

Bars join two headlands across a bay; cuspate forelands form between two converging longshore drifts.

Question 44

Why are depositional landforms considered unstable?

Answer 44

Made of unconsolidated sediment, easily eroded or reshaped by storms or sea-level change

Question 45

What is a sediment cell and why is it considered a closed system in theory?

Answer 45

A sediment cell is a stretch of coastline where the movement of sediment (inputs, transfers, and outputs) is largely self-contained. It is considered a closed system in theory because sediment doesn’t usually enter or leave the cell. This helps in managing the coast holistically, though in reality, some leakage can occur.