How do marine processes shape distinctive coastal landforms?
How marine erosion, transport and deposition create distinctive erosional and depositional landforms along the coast.
An Edexcel A-Level Geography answer to how marine processes shape the coast, covering erosion, transport and deposition and the erosional and depositional landforms they create using Old Harry Rocks, Spurn Head and Chesil Beach.
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What this dot point is asking
Edexcel wants you to explain how marine processes of erosion, transport and deposition operate, and how they create distinctive erosional and depositional landforms. You need the erosion processes, the four transport processes plus longshore drift, the controls on deposition, and the named landforms in each group with their formation.
Marine processes: erosion, transport and deposition
The four erosion processes act together. Hydraulic action forces air and water into joints, prising rock apart. Abrasion (or corrasion) flings sand and shingle at the cliff like sandpaper, the most effective process. Attrition rounds and shrinks the sediment itself as fragments collide. Solution (or corrosion) dissolves soluble rock such as chalk and limestone.
Transport moves this material four ways: traction rolls large clasts along the bed, saltation bounces sand, suspension carries fine particles in the water, and solution carries dissolved load. Along the coast, longshore drift dominates: waves driven by the prevailing wind break at an angle, so swash carries sediment obliquely up the beach while backwash returns it straight down, giving a net alongshore movement. This sets up swash-aligned beaches (waves parallel to the shore) and drift-aligned beaches (oblique waves moving sediment along).
Deposition occurs where energy falls, in sheltered bays and estuaries. Sediment is sorted by size as it settles, and fine clays in salty estuarine water clump together by flocculation, settling faster than they otherwise would.
Erosional landforms
Erosional landforms reflect rock resistance and structure. Cliffs retreat as a wave-cut notch is undercut at the high-tide line, the overhang collapses, and the cliff leaves behind a gently sloping wave-cut (shore) platform exposed at low tide.
On a headland, wave attack exploits lines of weakness in a sequence: a crack is widened to a cave, two caves meeting through a headland form an arch, the arch roof collapses to leave a stack, and continued erosion reduces the stack to a stump. The chalk of Old Harry Rocks displays this sequence clearly.
Depositional landforms
Where deposition dominates, the coast builds outward. Beaches form from sorted sediment, with berms (ridges marking high tides) and cusps (crescent hollows) on the surface.
A spit growing right across a bay becomes a bar, trapping a lagoon. A spit or bar joining the mainland to an island is a tombolo, as at Chesil Beach, which links to the Isle of Portland and impounds the Fleet lagoon. Offshore ridges parallel to the coast are barrier islands. Wind-blown sand builds sand dunes in a succession from embryo to fore, yellow, grey dunes and damp slacks. In sheltered estuaries, mud accumulates and vegetation colonises in a succession to form salt marshes.
Examples in context
Example 1: Old Harry Rocks and Swanage, Dorset. On this discordant coast, differential erosion has carved Swanage Bay into weak clays while resistant chalk forms the headland. At its tip, Old Harry Rocks shows the full crack-cave-arch-stack-stump sequence in chalk, with Old Harry himself a stack and a former stump nearby, a textbook erosional sequence on the Jurassic Coast.
Example 2: Spurn Head and Chesil Beach. Spurn Head is a 5 km recurved spit across the Humber, built from sediment supplied by Holderness eroding at around 1.8 m per year, with salt marsh sheltered behind. Chesil Beach is an 18 km shingle tombolo running from West Bay to Portland, its shingle sorted by size eastwards along its length, impounding the Fleet lagoon, both classic UK depositional landforms.
Try this
Q1. Explain how a wave-cut platform forms. [4 marks]
- Cue. A wave-cut notch is undercut at the high-tide line, the overhang collapses, the cliff retreats, and a gently sloping platform is left exposed at low tide.
Q2. Outline how sediment is transported along a coastline. [4 marks]
- Cue. Name traction, saltation, suspension and solution, then explain longshore drift: oblique swash and gravity-driven backwash give a net zigzag movement along the shore.
Exam-style practice questions
Practice questions written in the style of Pearson Edexcel exam questions on this dot point, with worked answer explainers. The year tag is the paper they imitate, not the source.
Edexcel Paper 1 (style)12 marksAssess the relative importance of geology in explaining the formation of coastal landforms.Show worked answer →
AO1 should outline the marine processes (hydraulic action, abrasion, attrition, solution) and transport by longshore drift, then AO2 should weigh geology against process and energy. Geology matters greatly for erosional landforms: differential erosion of resistant and weak rock on a discordant coast produces the headlands and bays at Swanage, Dorset, and the resistant chalk of Old Harry Rocks allows the crack-cave-arch-stack-stump sequence to survive. Structure (joints, faults, dip) controls where caves and arches open.
A balanced judgement (AO3) notes that depositional landforms such as the Chesil Beach tombolo and Spurn Head spit owe more to sediment supply, longshore drift and wave energy than to local lithology. The supported conclusion is that geology dominates erosional landforms while process and sediment budget dominate depositional ones, so importance depends on landform type.
Edexcel 20198 marksExplain how longshore drift leads to the formation of depositional landforms.Show worked answer →
AO1 and AO2. Define longshore drift: waves approaching at an angle drive swash up the beach obliquely, while backwash returns sediment straight down under gravity, producing a net zigzag movement of material along the coast. Explain that where the coast changes direction or energy falls, sediment is deposited.
Apply it. At Spurn Head on the Humber, drift fed by eroding Holderness boulder clay extends a spit across the estuary, with a recurved tip shaped by wave refraction and a sheltered salt marsh behind. At Chesil Beach, drift built a tombolo linking the mainland to the Isle of Portland, impounding the Fleet lagoon. Conclude that longshore drift supplies and moves the sediment that deposition then builds into spits, bars and tombolos.
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Sources & how we know this
- Pearson Edexcel A-Level Geography (9GE0) specification — Pearson Edexcel (2016)