Coasts

Question 1

• What is ‘hydraulic action’?

Answer 1

• where pounding waves compress trapped air in the rocks 🌊
  ➞ creating an explosive blast which weakens and loosens rock fragments ✨

Question 2

• What is ‘abrasion’?

Answer 2

• where rock fragments are thrown against the headland 🌄
  ➞ breaking down the cliff face, wearing away the rock

Question 3

• What is ‘solution’?

Answer 3

• where carbonic acid in the sea water dissolves soluble rocks 🌊

Question 4

• What is the formation of a ‘wave-cut platform’?

Answer 4

🟢 BEGINNING:
* Cliffs contain lines of weaknesses that are more easily eroded 🌄

• A line of weakness is undercut by erosion 🌊
  ➞ to form a WAVE-CUT NOTCH

🟠 MIDDLE (PROCESSES):
* Erosion takes place by:
➞ hydraulic action (where pounding waves compress trapped air in the rocks, creating an explosive blast which weakens and loosens rock fragments)
➞ abrasion (where rock fragments are thrown against the headland, breaking down the cliff face, wearing away the rock)
➞ solution (where carbonic acid in the sea water dissolves the rocks)

🔵 ENDING (FINAL PROCESSES):
* Overtime, the wave-cut notch becomes enlarged by continued erosion
➞ creating undercutting and an overhang.

• As the overhang is unsupported
  ➞ it collapses due to its own weight and gravity.
• This causes the cliff to retreat in-land,
  ➞ leaving a gently sloping platform called a WAVE-CUT PLATFORM
  ↳ (e.g. Kimmeridge Bay)
• The platform is then abraded by rock materials,
  ➞ with rock pools and pot holes forming - visible at low tide.

Question 5

• What is the formation of a ‘bay & headland’?

Answer 5

🟢 BEGINNING:
* Bays and headlands occur in discordant coastlines 🌊
➞ alternating bands of hard (chalk) and soft rock (clay) at right angles to the coast.

• DIFFERENTIAL EROSION
  ➞ occurs where soft rock is eroded faster than the stronger hard rock

🟠 MIDDLE (PROCESSES):
* Erosion takes place by:
➞ hydraulic action (where pounding waves compress air trapped in the rocks, creating an explosive blast which weakens and loosens rock fragments)
➞ abrasion (where rock fragments are thrown against the headland, breaking down the cliff face, wearing away the rock)
➞ solution (where carbonic acid in the sea water dissolves the rocks)

🔵 ENDING (FINAL PROCESSES):
* This leaves the hard rocks jutting out into the sea
➞ forming a headland
↳ and the soft rock as a sheltered area between the hard rock
➞ forming a bay
(e.g. Duriston Bay)

• Constructive waves build a small beach in the sheltered bay between the headlands.

Question 6

• What is the formation of a ‘stack’?

Answer 6

🟢 BEGINNING:
* Headlands contain lines of weakness that are more easily eroded 🌄

🟠 MIDDLE (PROCESSES):
* Erosion takes place by:
➞ hydraulic action (where pounding waves compress air trapped in the rocks, creating an explosive blast which weakens and loosens rock fragments)
➞ abrasion (where rock fragments are thrown against the headland, breaking down the cliff face, wearing away the rock)
➞ solution (where carbonic acid in the sea water dissolves the rocks)

🔵 ENDING (FINAL PROCESSES):
* Overtime, the line of weakness is enlarged into a cave .

• A blowhole can form in the roof of the cave
  ➞ as compressed air is pushed upwards by the power of the waves, causing vertical erosion.
• There may be erosion of both sides of the headland due to wave refraction,
  ➞ until the sea cuts through the backwalls of the cave, forming an arch.
• Continued erosion enlargens the arch and the base is undercut by erosion
  ➞ causing it to become unsupported.
• Eventually, the arch will collapse due to its own weight and gravity to form a stack
  ➞ (e.g. Old Harry)

Question 7

• What is the formation of a ‘spit’?

Answer 7

🟢 BEGINNING:
* Spits are formed where there is a change in direction in the coastline 🏖️
➞ creating a sheltered area for deposition.

🟠 MIDDLE (PROCESES):
* Spits are formed by longshore drift 🌊
➞ where sand is moved along the coast in a zig-zag pattern.

• Sand is moved by swash
  ➞ where the water moves material up the beach at an angle due to prevailing wind direction.
• Backwash
  ➞ then brings material down the beach at right angles due to gravity.

🔵 ENDING (FINAL PROCESSES):
* A hook forms at the end of the spit 🪝
➞ due to a change in the wind direction and currents.

• Overtime, the material builds up and appears above the water ⛱️
  ➞ It will continue to develop as long as the amount of new deposits is greater than erosion.
• A saltmarsh forms in the sheltered area behind the spit.
• (e.g. Sand Banks)
  .

Question 8

• What is the formation of a ‘sand bar’?

Answer 8

🟢 BEGINNING:
* Spits are formed where there is a change in direction in the coastline 🏖️
➞ creating a sheltered area for deposition.

🟠 MIDDLE (PROCESES):
* Spits are formed by longshore drift 🌊
➞ where sand is moved along the coast in a zig-zag pattern.

• Sand is moved by swash
  ➞ where the water moves material up the beach at an angle due to prevailing wind direction.
• Backwash
  ➞ then brings material down the beach at right angles due to gravity.

🔵 ENDING (FINAL PROCESSES):
* A sand bar is formed when a spit grows across a bay, joining two headlands
➞ creating a lagoon.

• Overtime, the material builds up and appears above the water ⛱️
  ➞ It will continue to develop as long as the amount of new deposits is greater than erosion.
• Overtime, the lagoon will be filled in by deposition.
• (e.g. Christchurch Harbour)

Question 9

• What is the formation of a ‘tombolo’?

Answer 9

🟢BEGINNING:
* Spits are formed where there is a change in direction in the coastline 🏖️
➞ creating a sheltered area for deposition.

🟠 MIDDLE (PROCESES):
* Spits are formed by longshore drift 🌊
➞ where sand is moved along the coast in a zig-zag pattern.

• Sand is moved by swash
  ➞ where the water moves material up the beach at an angle due to prevailing wind direction.
• Backwash
  ➞ then brings material down the beach at right angles due to gravity.

🔵 ENDING (FINAL PROCESSES):
* Overtime, the material builds up and appears above the water ⛱️
➞ It will continue to develop as long as the amount of new deposits is greater than erosion.

• A tombolo is formed when the spit extends out from the mainland and connects on to an island
  ➞ as the waves are not strong enough to erode it.
• (e.g. Chesil Beach)