Physical Geography - Coasts

Question 1

L8 Give the 4 types of erosion and define them

Answer 1

Abrasion - pebbles hurled at the cliff base by the waves causing erosion

Hydraulic action - waves cause air to be trapped in joints at high pressure which ‘explodes’ outwards as the waves retreat

Attrition - Wearing down of rocks by impact, gradually making stones rounder and smaller

Solution - Alkaline cliffs (chalk, limestone) are eroded by weakly acidic seawater

Question 2

L8 What 2 things cause different rates of erosion?

Answer 2

Energy in waves, lithology - joints, bedding planes, faults, resistance - leading to differential erosion

Question 3

L8 Describe how a wave cut platform is formed

Answer 3

Waves erode away the base of the cliff, cliff becomes unstable and collapses, rock is broken up and used in attrition to erode away the new cliff, cliff retreats

Question 4

L9 Describe the 4 processes of marine transportation

Answer 4

Suspension - lighter sediment floats

Traction - large, heavy rocks roll along the seabed

Solution - dissolved sediment

Saltation - smaller rocks bounce along the seabed

Question 5

L9 Describe the process of Longshore Drift

Answer 5

Swash hits the coast at an angle due to the prevailing wind, backwash is perpendicular to the coast due to gravity, sediment is transported up the beach

Question 6

L9 Describe the formation of a spit and give an example

Answer 6

Longshore drift causes sediment to travel along a coast until the coast suddenly changes direction (e.g. an estuary), if this happens sediment is deposited, the end of a spit will begin to curve round due to wave refraction which carries material into the more sheltered water behind the spit, e.g. Spurn Point

Question 7

L10 Describe the formation of a beach, give examples

Answer 7

Accumulation of sand/shingle, formed due to constructive waves, swash carries material up the shore but backwash has little energy so material is deposited, e.g. WSM, Blackpool, Southend

Question 8

L10 Describe the formation of an offshore bar and give 2 examples

Answer 8

Sediment is eroded by destructive waves and deposited by backwash, located at offshore/nearshore boundary where the water particle orbit no longer reaches the seabed, used to construct wind farms or as a source of sand for beach nurishment, e.g. Loe Bar, Cornwall or Slapton Sands, Devon

Question 9

L10 Describe what a bar is, give two ways they’re formed, and give an example

Answer 9

Linear ridges of sand that extend completely across a bay, e.g. Chesil Beach

Formed in 2 ways:
- LSD extends a spit across the width of a bay
- Rising sea levels cause constructive waves to drive a ridge of sediment onshore to coastlines with a gently sloping shallow sea bed (barrier beach)

Question 10

L10 Describe what a tombolo is, 2 ways they can form, and give examples

Answer 10

Linear ridges of sand connecting an offshore island to the coastline, e.g. St Ninian’s tombolo, Shetland Islands or Portland Bill

Formed by:
- LSD which builds a spit which connects to the island
OR
- Wave refraction around both sides of the island, creates a collision of waves which cancel each other out, creates a still environment where deposition takes place

Question 11

L10 Describe what a Cuspate Foreland is, how they’re formed, and give an example

Answer 11

Low lying triangular headlands extending out from the shoreline, e.g. Dungeness Kent (11km)

LSD currents from opposite directions converge at the boundary between two sediment cells, sediment is deposited out into the sea by both currents