- Created by: K4t13
- Created on: 02-06-15 17:48
Cliff and Wave-Cut Platforms
- A narrow flat area often found at the base of a cliff which was created by the action of waves.
- Wave-cut platforms are often most obvious at low tide when they become viable as huge areas of flat land.
1. Sea Erodes
the erosion of a cliff is greatest at its base were large waves break- hydraulic actions, scouring and wave pounding actively undercut the foot og the cliff forming an indent called a wave-cut notch whislt the cliff face is also affected by abrasion as rock fragemtns are hurled againest the cliff by the breaking waves.
2. Wave-Cut Notch Weakening Cliff
this undercutting continues and eventually the over hanging cliff collapses downwards- this process continues and the cliff gradually retreats and becomes steeper.
3. Cliff Collapses
as the cliff retreats, a gently-slopping rocky platform is left at the base, this is known as a wave-cut platform which is exposed at low tide.
Headlands and Bays
- Headlands form along discordant coastlines in which bands of soft and hard rock outcrops at right angles to the coastline.
- Due to the presence of soft and hard rock, differential erosion occurs, with the soft, less resistant rock eroding quicker than the hard, resisitant rock.
- Where the erosion of the soft rock is rapid, bays are formed.
- Where there is more resistant rock, erosion is slower and the hard rock is left sticking out into the sea as a headland.
- The exposed headland now becomes vulnerable to the force of destructive waves but shelters the adjacent bays from further erosion.
Cave, Arch, Stack, Stump
- Weak areas are attacked by waves and opened to form a CAVE. (due to erosion(HA))
- Cave widened and deepened by erosion to form an ARCH.
- As the roof of the arch is continually undercut it eventually collapses leaving an isolated STACK.
- Stack is continuously eroded eventuslly forming a STUMP.
- The formation of a spit begins due to a change in the direction of a coastline - the main source of material building up a spit is from longshore drift which brings material from further down the coast.
- where there is a break in the coastline, longstore drift will deposit material at a faster rate than it can be removed and gradually a ridge is built up.
- A change in prevailing wind direction often causes the end of spits to become hooked.
- On the spit itself, sand dunes often form and vegetation colonizes.
- Water is trapped behind the spit and as the water begins to stagnate, mud and marshland develops.
- Spits may continue to grow until deopostition can no longer occur due the the current and force of water moving from a river.
- These form in the same way as a spit initally but bars are created where a spit grows across a bay, joining to headlands.
- Behind a bar, a lagoon is created, where water has been trapped and the lagoon mat gradualy be infilled as a salt marsh develops due to it being a low energy zone, which encourages depostion.
- An example of a bar: Slapton Sands, Devon
- Beaches are the main features of depostion foud at the coast.
- These consist of all the material (sand, shingle etc.) that has built up between the high and low tide marks. There are a number of different sources of beach material- the main source being rivers, where fine muds and gravels are deposited at the river mouth.
- Other sources of beach material include longshore drift (bringing material from elsewhere along the coast); constructive waves (bring material up the beach from the sea) and from cliff erosion.
- As constructive waves build up beaches, they often frm ridges in the beach known as berms.
Hard/Soft Engineering Methods
- Recurved Wall
- RIp Rap/ Rock Armour
- Beach Replenishment
- Cliff Re-Grading/ Re-Profiling