Physical - Coasts Flashcards
Swash
The wave going into the beach
Sand spit
A coastal feature created by the process of longshore drift. A long narrow ridge of sand or shingle that extends out to sea and is joined to the main land at one end.
Backwash
The retreating wave
Longshore drift
The movement of material along the coast in the direction of the prevailing wind
Constructive wave
A low-energy wave that has a stronger swash than backwash creates beaches through coastal deposition
Destructive wave
A high-energy wave that has a stronger backwash than swash, created during high wind. Erodes coast.
Abrasion
Loose rocks (sediment) are thrown against the cliff by waves, wearing the cliff away by smoothing them like sandpaper
Attrition
Rocks knock against each other, causing them to break apart and become more rounded
Hydraulic action
Waves force water into cracks in the rock. This compresses the air in the rock, causing the rock to weaken and eventually break apart
Solution
Salt and other chemicals in the sea dissolve soft rocks such as limestone and chalk
Fetch
How far a wave has travelled
Factors affecting the rate of coastal erosion
(2 points)
- Resistance of rock - the harder a rock is, the harder it is to be worn away so it will erode slower than soft rock
- Wave fetch - the further a wave has travelled the more force it has
Headland
An area of hard rock extending into the sea
Bay
An inlet between two headlands, usually formed by soft rock
Formation of headlands and bays
(4 steps)
- Bands of alternating hard and soft rock meet the coast at right angles
- Differential erosion occurs as the sea erodes the softer rock faster than the harder rock, forming bays
- Where there is harder rock, headlands are left extending out beyond the bays
- The bays are sheltered by the headlands, which absorb the energy of the waves. This causes erosion to slow down in the bays and deposition occurs, forming a beach
To get full marks, 2 processes of coastal erosion must be mentioned (e.g. hydraulic action and abrasion)
Formation of caves, arches, stacks, and stumps
(5 steps)
- Hydraulic action makes a small crack in a headland larger
- Continuous erosion opens up the crack, and it forms a sea cave
- Further erosion of the cave will eventually cause it to break through the headland, forming an arch
- Waves continue to erode the arch until the roof collapses, leaving behind a freestanding tower of rock called a stack
- The stack is continuously eroded until it eventually falls over, creating a stump
Wave - cut notch
A notch in the base of a cliff, formed when a cliff is undercut by waves
Wave - cut platform
A platform made of flat rock at the base of a cliff, formed when a cliff retreats
Formation of a wave - cut platform
(4 steps)
- Erosion takes place where the waves hit the shore, forming a wave - cut notch
- The notch is further eroded to leave an overhang above
- Further erosion causes the overhang to collapse into the sea, leaving a cliff behind
- Continuous erosion causes the cliff to retreat inland, leaving a wave - cut platform behind
Formation of a lagoon
(3 steps)
- When the coast changes direction, longshore drift continues to deposit sand in a straight line
- The sand will build up until it is above sea level, causing a sand spit to form
- When a sand spit forms across the mouth of a bay (only if there is no river), a sand bar is formed
- The pool trapped behind the sand bar goes stagnant and is called a lagoon
Sand spits can develop curved ends due to changes in wind direction
Tombolo
When a spit joins an island to the mainland it is called a tombolo
Cliff
Steep sided rock face
Cave
Hollow in the side of a cliff
Beach
Strip of sand and stones next to the sea
Stack
Rocky pillar surrounded by water
Arch
Hole passing right through a headland
