COASTS: Coastal Landforms Flashcards
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?
Beaches
Spits
Offshore bars and tombolos
Barrier islands
Sand dunes
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?
Berms
Runnels
Cusps
Berms
Ridges of sand and pebbles found at high tide marks.
Runnels
Grooves in the sand running parallel to the shore, formed by backwash draining to the sea.
Cusps
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.
Compound spit
A spit that has multiple recurved ends resulting from several periods of growth.
Simple spit
A straight spit that grows out roughly parallel to the coast.
What often forms in the area behind a spit?
Why?
Mudflats and saltmarshes.
Because the area is sheltered.
Bars
Formed when a spit joins two headlands together, eg. across a bay or the mouth of a river.
What can form behind a bar?
A lagoon.
Offshore bars
Bars that form off the coast when material moves towards the coast - these are partly submerged.
Tombolo
A bar that connects the shore to an island.
Barrier 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.
Ridges of sand and pebbles found at high tide marks.
Berms
Grooves in the sand running parallel to the shore, formed by backwash draining to the sea.
Runnels
Crescent-shaped indentations that form on beaches of mixed sand and shingle.
Cusps
A spit that has multiple recurved ends resulting from several periods of growth.
Compound spit
A straight spit that grows out roughly parallel to the coast.
Simple spit
Formed when a spit joins two headlands together, eg. across a bay or the mouth of a river.
Bars
A lagoon.
What can form behind a bar?
Bars that form off the coast when material moves towards the coast - these are partly submerged.
Offshore bars
A bar that connects the shore to an island.
Tombolo
Long, narrow islands of sand or gravel that run parallel to the shore and are detached from it.
Barrier island
There are 7.
What are the coastal zones?
Offshore
Nearshore
Foreshore
Backshore
Swash zone
Breaker zone
Surf zone
Offshore
Beyond the point where waves have an impact on the seabed.
Nearshore
Between the low water mark and the area where waves cease to have an influence on the seabed.
Forshore
Between the high water mark and low water mark.
Backshore
Above the high water mark up to the landward limit of marine activity.
Swash zone
Turbulent water rushed up to the beach - swash.
Breaker zone
Waves approaching the shore begin to break.
Surf zone
The area between the waves breaking and moving up the beach as swash.
Beyond the point where waves have an impact on the seabed.
Offshore
Between the low water mark and the area where waves cease to have an influence on the seabed.
Nearshore
Between the high water mark and low water mark.
Forshore
Above the high water mark up to the landward limit of marine activity.
Backshore
Turbulent water rushed up to the beach - swash.
Swash zone
Waves approaching the shore begin to break.
Breaker zone
The area between the waves breaking and moving up the beach as swash.
Surf zone
Give an example of caves, arches and stacks:
Old Harry, Swanage
Give an example of cliffs and wave cut platforms:
Watchet, West Somerset
Give an example of headlands and bays:
Swanage Bay
Give an example of simple and compound spits:
Sandbanks, Hurst Castle, Spurn Point
Give an example of a tombolo:
Chesil Beach joining the Isle of Portland
Give an example of offshore bars:
Hordle Cliff
Give an example of barrier islands:
Fire Island / Long Island - New York
Give an example of a bar/barrier beach:
Slapton Sands
Give an example of sand dunes:
Oxwich
Give an example of saltmarshes/mudflats:
Keyhaven Marshes
