How do marine and sub-aerial processes shape distinctive coastal landforms?
Coastal landforms and processes: waves, marine and sub-aerial processes, erosional landforms (headlands and bays, caves, arches, stacks, stumps, wave-cut platforms) and depositional landforms (beaches, spits, bars), and a UK coastal landscape.
An Eduqas GCSE Geography A (C111) answer to coastal landforms and processes in Theme 1, covering constructive and destructive waves, marine and sub-aerial processes, erosional landforms (headlands, caves, arches, stacks, wave-cut platforms), depositional landforms (beaches, spits, bars) and a UK coastal landscape.
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What this dot point is asking
This is part of Eduqas GCSE Geography A (C111) Theme 1, Landscapes and Physical Processes, assessed in Component 1, Changing Physical and Human Landscapes. Eduqas expects you to know the difference between constructive and destructive waves, the marine and sub-aerial processes that shape coasts, how these create erosional landforms (headlands and bays, caves, arches, stacks, stumps, wave-cut platforms) and depositional landforms (beaches, spits, bars), and to study one UK coastal landscape with named landforms.
Waves: constructive and destructive
Waves are the main source of energy at the coast, and Eduqas wants you to distinguish two types.
Marine and sub-aerial processes
Two families of process shape every coast.
- Marine processes are the work of the sea. Erosion: hydraulic action (the force of water and trapped air compressing into cracks), abrasion (waves hurling sand and pebbles at the cliff), attrition (rock fragments knocking together and rounding off) and solution (acids dissolving limestone and chalk). Transport: mainly longshore drift, the zig-zag movement of sediment along the coast. Deposition happens when waves lose energy.
- Sub-aerial processes are land-based and attack the cliff from above and behind. Weathering (freeze-thaw shattering, carbonation dissolving) loosens the rock; mass movement (rockfalls, slumping of saturated clay) moves it downslope to the foot of the cliff.
Longshore drift
Longshore drift moves sediment along the coast. The prevailing wind drives waves onto the beach at an angle, so the swash carries material up the beach diagonally; gravity then pulls the backwash straight back down the steepest slope. Repeated, this produces a zig-zag movement of sediment along the coast, which supplies the material for depositional landforms further along.
Erosional landforms
On exposed, resistant coasts the sea cuts a recognisable set of landforms.
- Headlands and bays form on a discordant coast where bands of hard and soft rock meet the sea at right angles: the soft rock is eroded back into bays, while the resistant rock juts out as headlands.
- On a headland, the sea attacks a crack or joint, widening it into a cave; erosion cuts the cave through the headland to form an arch; the unsupported roof collapses to leave a stack; the stack is worn down to a stump (the cave-arch-stack-stump sequence, as at Old Harry Rocks).
- A wave-cut platform forms as waves erode a wave-cut notch at the base of a cliff; the overhang collapses and the cliff retreats, leaving a gently sloping rocky platform exposed at low tide.
Depositional landforms
Where the sea loses energy and drops its load, deposition builds new land.
- A beach forms where constructive waves deposit sand and shingle in a bay; sand makes a gently sloping beach, shingle a steeper one.
- A spit is a long, narrow ridge of sand and shingle that grows out across a bay or river mouth: longshore drift carries sediment along the coast, and where the coast changes direction the material is deposited in the deeper, sheltered water, building outwards. The end is often recurved by wave refraction, and a salt marsh develops in the sheltered water behind (Spurn Head on the Holderness coast).
- A bar forms when a spit grows right across a bay, sealing off a lagoon behind it.
A UK coastal landscape
Eduqas requires one UK coast studied in detail. A common choice is the Dorset coast (the Jurassic Coast): its discordant section has Swanage Bay between the Ballard Down and Durlston Head headlands, with the Old Harry Rocks stacks and stumps on the chalk; its concordant section near Lulworth Cove shows how the sea breaks through a hard outer rock band to erode the softer rock behind. Another popular study is Holderness, the fastest-eroding coastline in Europe, with Spurn Head spit at its southern end. Learn the named landforms and the processes that made them.
Try this
Q1. Explain how an arch is formed from a cave. [4 marks]
- Cue. The sea erodes a cave through a headland by hydraulic action and abrasion until it cuts right through to form an arch.
Q2. Explain how a spit is formed. [4 marks]
- Cue. Longshore drift moves sediment along the coast; where the coast changes direction, material is deposited in sheltered water and builds outward, often with a recurved end and salt marsh behind.
Exam-style practice questions
Practice questions written in the style of WJEC Eduqas exam questions on this dot point, with worked answer explainers. The year tag is the paper they imitate, not the source.
Eduqas 2019 (style)4 marksExplain the formation of a stack. (Component 1)Show worked answer →
A 4-mark "Explain" question assessing AO1 and AO2 of a sequenced landform. Markers reward the ordered cave-arch-stack sequence, not a list.
Award credit for: waves attack a line of weakness (a crack or joint) in a resistant headland by hydraulic action and abrasion, widening it into a cave. Continued erosion cuts the cave right through the headland to form an arch. Weathering attacks the roof of the arch from above while the sea erodes the base, until the unsupported roof collapses, leaving an isolated pillar of rock called a stack (Old Harry Rocks on the Dorset coast). Later erosion wears the stack down to a stump. Top answers keep the sequence in order and name the processes.
Eduqas 2021 (style)6 marksUsing a UK coastal landscape you have studied, explain how marine and sub-aerial processes have created its landforms. (Component 1)Show worked answer →
A 6-mark levels-of-response question assessing AO1 and AO2, requiring a named UK coast.
Strong answers take a studied coast (such as the Dorset coast or Holderness) and link processes to landforms. Explain that discordant coastlines, where bands of hard and soft rock meet the sea at right angles, are eroded differentially: the soft rock retreats to form bays and the hard rock juts out as headlands (Swanage Bay between Ballard Down and Durlston Head). On the headlands, marine erosion (hydraulic action, abrasion) cuts caves, arches and stacks (Old Harry Rocks), while sub-aerial processes (freeze-thaw weathering, mass movement) attack the cliff face from above. Depositional landforms such as the spit at Hurst Castle or the beaches in the bays form where longshore drift moves and drops sediment. A good answer names the coast and ties each process to a specific landform. Markers reward the named coast and the process-landform link.
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Sources & how we know this
- WJEC Eduqas GCSE (9-1) Geography A specification (C111) — WJEC Eduqas (2016)