List coastal landforms caused by erosion:
Cliffs and wave cut platforms
Headlands and bays
Caves, arches and stacks
How do cliffs form?
- Sea erodes the land.
- Overtime, cliffs retreat due to wave action and weathering.
How do wave-cut platforms form?
- Waves attack base of cliff, via abrasio and hydraulic action.
- Creates a wave-cut notch which is undercut.
- This becomes unstable and collapses.
- Notch migrates inland and cliff retreats.
- Wave cut platform is smoothed via abrasion and solution.
How are headlands and bays formed?
- Formed on discordant coastlines.
- Soft rock is eroded quickly, forming a bay.
- Hard rock is eroded less and forms a headland.
How are caves, arches and stacks formed?
- Weak areas in rock / joints are eroded to form caves.
- Caves on opposite sides of the narrow headland join to form an arch.
- When an arch collapses, it forms a stack.
What coastal landforms are caused by deposition?
Offshore bars and tombolos
Estuarine mudflats and salt marshes
How are beaches formed?
Constructive waves deposit sediment on the shore.
What is the differences between shingle and sand beaches?
- Shingle beaches are steep, narrow and made of larger particles.
- Sand beaches are wide, flat and made of smaller particles.
What are 3 distinctive features of a beach?
Ridges of sand and pebbles found at high tide marks.
Grooves in the sand running parallel to the shore, formed by backwash draining to the sea.
Crescent-shaped indentations that form on beaches of mixed sand and shingle.
Where do spits tend to form?
When the coastline changes direction.
How are spits formed?
- LSD continues to dpeosit material across the river mouth, leaving a bank of sand and shingle sticking out.
- Occasional changes to dominant wind direction may lead to spit having a recurved end.
- Recurved ends can be abandoned as the waves return to their original direction - compound spit.
A spit that has multiple recurved ends resulting from several periods of growth.
A straight spit that grows out roughly parallel to the coast.
What often forms in the area behind a spit?
Mudflats and saltmarshes.
Because the area is sheltered.
Formed when a spit joins two headlands together, eg. across a bay or the mouth of a river.
What can form behind a bar?
Bars that form off the coast when material moves towards the coast - these are partly submerged.
A bar that connects the shore to an island.
Long, narrow islands of sand or gravel that run parallel to the shore and are detached from it.
Where do barrier islands tend to form?
- Good supply of sediment.
- Gentle slope offshore
- Fairly powerful waves
- Small tidal range
What are the two theories behind the formation of barrier islands?
- Rapid ice melting from last ice age flooded the land behind beaches and transported sand offshore, where it was deposited in shallow water.
- Islands were orignally bars, attached to the coast, which were eroded in sections causing breaches in the bar.
What often forms behind a barrier island?
Lagoon or marsh
How are sand dunes formed?
- Sand deposited by LSD is moved up the beach by the wind.
- Sand is trapped by driftwood or berms and is colonised by plants and grasses.
- Vegetation stabilises the sand and encourages more sand to accumulate.
- Embryo dunes form.
- Oldest dunes migrate inland - mature dunes.
Where do mudflats and saltmarshes form?
In sheltered, low-energy environments.
How are mudflats formed?
Mud and silt is deposited by the rive or the tide.
How are saltmarshes formed?
- Mudflats are colonised by vegetation that can survive the high salt levels and long submergence periods.
- Plants trap more mud and ailt.
- Builds upwards to create an area of saltmarsh that remains exposed for longer and longer between tides.
Erosion by tidal currents or streams results in the formation of what in the surface of mudflats or saltmarshes?
Channels which may be permanently flooded or dry at low tide.