Coastal Landforms (Edexcel IGCSE Geography)
Revision Note
Written by: Jacque Cartwright
Reviewed by: Bridgette Barrett
Erosional Landforms
Headland and bay
Found in areas of alternating bands of resistant (hard) and less resistant (soft) rocks running perpendicular to oncoming waves (discordant coastline)
Initially, less resistant rock (e.g. clay) is eroded back, forming a bay
A bay is an inlet of the sea where the land curves inwards, usually with a beach
The more resistant rock (e.g. limestone) is left protruding out to sea as a headland
Cove
A cove forms where the coastline has bands of resistant and less resistant rock running parallel to the oncoming waves (concordant coastline)
There is usually a band of resistant rock facing the oncoming waves, with a band of softer rock behind
Wave processes of abrasion, corrosion and hydraulic action will exploit faults in the resistant rock and erode through to the softer rock
Further wave action will erode the softer rock quickly, which will leave behind a circular cove with a narrow entrance to the sea
Wave refraction within the cove spreads out the erosion in all directions, creating the typical horseshoe shape
Lulworth Cove in Dorset, UK, is a good example of a cove
Cliff and wave-cut platform
Cliffs are shaped through erosion and weathering processes
Less resistant rock erodes quickly and will form sloping cliff faces
Steep cliffs are formed where there is harder rock facing the sea
A wave-cut platform is a wide gently sloped surface found at the foot of a cliff:
As the sea attacks the base of a cliff between the high and low water mark, a wave-cut notch is formed
Abrasion, corrosion and hydraulic action further extend the notch back into the cliff
The undercutting of the cliff leads to instability and collapse of the cliff
The backwash of the waves, carries away the eroded material, leaving behind a wave-cut platform
The process repeats and the cliff continues to retreat, leading to a coastal retreat
Cave, arch, stack and stump
Found on a headland due to wave action and sub-aerial weathering
Any weaknesses in the headland are exploited by erosional processes of hydraulic action, abrasion and corrosion
As the crack begins to widen, abrasion will begin to wear away at the forming cave
The cave will become larger and eventually break through the headland to form an arch
The base of the arch continually becomes wider and thinner through erosion below and weathering from above
Eventually, the roof of the arch collapses, leaving behind an isolated column of rock called a stack
The stack is undercut at the base by wave action and sub-aerial weathering above until it collapses to form a stump
Depositional Landforms
Beach
Form in sheltered areas such as bays
Deposition occurs through constructive wave movement, where the swash is stronger than the backwash
Beach formation usually occurs in the summer months when the weather is calmer
Sometimes sand from offshore bars can blow onto the shore by strong winds
Blown sand can create sand dunes at the backshore of a beach
Spit
An extended stretch of sand or shingle that extends out to sea from the shore
Spits occur when there is a change in the shape of the coastline
Or the mouth of a river, which prevents a spit from forming across the estuary
A spit may or may not have a 'hooked' end, depending on opposing winds and currents
A good example is Spurn Point, which stretches for three and a half miles across the Humber Estuary in the northeast of England
Stages of Formation:
Sediment is transported by longshore drift
Where the coastline changes direction, a shallow, sheltered area allows for deposition of sediment
Due to increased friction, more deposition occurs
Eventually, a spit slowly builds up to sea level and extends in length
If the wind changes direction, then the wave pattern alters and results in a hooked end
The area behind the spit becomes sheltered
Silts are deposited here to form salt marshes or mud flats
Bar
When a spit grows across a bay, and joins two headlands together
A bar of sand is formed (sandbar)
Sandbars can also form offshore due to the action of breaking waves from a beach
Lagoon
A lagoon is where a small body of water is cut off from the sea
A lagoon may form behind a bar or tombolo
Lagoons do not last forever and may fill with sediment and form new land
Tombolo
A tombolo is formed when a spit joins the mainland to an island
Chesil Beach in Dorset is a tombolo, as the mainland is joined to the Isle of Portland
Barrier Island
Barrier islands form parallel to the coast
The main difference between a bar and barrier island is that a bar joins two headlands, whereas a barrier island is open at one or both ends
Examiner Tips and Tricks
You may be asked to draw and label a diagram showing how depositional landforms (beaches, spits etc.) are formed. You need to be able to show how sediment is transported along the coast by waves. Practice drawing and labelling these diagrams so you can reproduce any of them in the exam. Marks will be awarded for the accuracy and completeness of your labelling and drawing.
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