Coasts Flashcards
- What is ‘hydraulic action’?
- where pounding waves compress trapped air in the rocks 🌊
➞ creating an explosive blast which weakens and loosens rock fragments ✨
- What is ‘abrasion’?
- where rock fragments are thrown against the headland 🌄
➞ breaking down the cliff face, wearing away the rock
- What is ‘solution’?
- where carbonic acid in the sea water dissolves soluble rocks 🌊
- What is the formation of a ‘wave-cut platform’?
🟢 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.
- What is the formation of a ‘bay & headland’?
🟢 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.
- What is the formation of a ‘stack’?
🟢 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)
- What is the formation of a ‘spit’?
🟢 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)
.
- What is the formation of a ‘sand bar’?
🟢 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)
- What is the formation of a ‘tombolo’?
🟢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)
