The big idea: The coast is shaped by three families of process working together.
Marine processes — what the sea does: erosion (waves wearing rock away), transport (moving sediment along the coast), deposition (dropping sediment to build beaches and dunes).
Subaerial processes — what the land and air do above the waterline: weathering (rock breaking up in place) and mass movement (material sliding or slumping down a cliff).
These processes build landforms of erosion (cliffs, stacks, wave-cut platforms) and landforms of deposition (beaches, spits, sand dunes), while changes in sea level create whole emergent or submergent coasts (raised beaches, fjords).
Key terms you must be able to use
- Marine erosion — waves wearing the coast away (hydraulic action, abrasion, attrition, solution).
- Longshore drift — the zig-zag transport of sediment along a coast by waves hitting it at an angle.
- Deposition — sediment dropped where the sea loses energy, building beaches, spits and bars.
- Subaerial process — weathering or mass movement acting on the coast from above the waterline (NOT the sea).
- Lithology — the rock type and its resistance; hard rock erodes slowly, soft rock fast.
- Eustatic / isostatic change — a global rise/fall of the sea (eustatic) vs the land rising/sinking (isostatic).
Marine vs subaerial — a marked distinction: Examiners separate the two.
Marine = the sea doing the work (waves, hydraulic action, abrasion).
Subaerial = the land/air doing the work (frost weathering, salt weathering, rockfall, slumping). If a question asks for a subaerial process, naming a wave process scores zero.
How this is tested: Paper 1 Option B opens with data-response on a coastal stimulus — a photo or an OS map. You Identify landforms from a photograph, State a six-figure grid reference, or Estimate a distance from the scale. Then short Outline / Explain parts test the processes behind the landforms. Always read the correct feature and quote units.
| Stage | What happens | Landform you see |
|---|---|---|
| 1 Weakness attacked | Waves exploit a crack or fault in the rock by hydraulic action + abrasion | A notch, then a sea cave |
| 2 Cave cuts through | The cave is eroded right through a narrow headland | An arch |
| 3 Roof collapses | The unsupported arch roof falls under gravity (mass movement) | A stack (isolated pillar) |
| 4 Stack undercut | The stack is undercut and collapses to a stump | A stump |
| 5 Base trimmed back | The cliff retreats, leaving a gently sloping rock bench at its foot | A wave-cut platform |
How to read a coastal photo or map
- Identify landforms — name the cliff, stack, arch, wave-cut platform, headland or bay you can see.
- Six-figure grid reference — read eastings first (along the corridor), then northings (up the stairs), each to one extra estimated digit.
- Estimate a distance — measure the straight line, then convert using the scale (on a 1:25 000 map, 4 cm on the map = 1 km on the ground).
- Link feature to process — a stack means past arch collapse; a wave-cut platform means cliff retreat.
Real coast — Cape Foulwind, New Zealand: The Cape Foulwind coast on the South Island of New Zealand is a classic high-energy, eroding shore.
Strong Tasman Sea swells have cut headlands, sea stacks and a wave-cut platform into the rock — exactly the erosional landforms a photo-response question asks you to identify.
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Not all coastal change comes from the sea. Subaerial processes attack the coast from above the waterline and feed sediment to the beach. Deposition then builds beaches, spits and sand dunes where the sea and wind lose energy, and vegetation locks the loose sand in place.
| Process | How it weakens the coast |
|---|---|
| Freeze-thaw weathering | Water in cracks freezes, expands and prises the rock apart |
| Salt weathering | Sea-spray salt crystallises in pores and grows, crumbling the rock |
| Biological weathering | Plant roots and burrowing animals widen cracks in the cliff |
| Mass movement (slumping/rockfall) | Weakened, rain-soaked rock slides or falls down the cliff under gravity |
| Running water | Rainwater running over the cliff face washes loose material away |
| Stage | What happens |
|---|---|
| 1 Sand supply | A wide sandy beach dries at low tide, giving loose sand the wind can move |
| 2 Wind transport | Onshore wind rolls and bounces sand grains landward across the beach |
| 3 An obstacle traps sand | Sand piles up behind driftwood or a tuft of pioneer grass (an embryo dune) |
| 4 Vegetation colonises | Salt-tolerant pioneers like marram grass take root and slow the wind further |
| 5 The dune grows + fixes | Roots bind the sand and dead plants add humus, so a tall, stable dune builds up inland |
How vegetation helps a dune form and grow
- Traps wind-blown sand — leaves and stems act as a barrier, so sand drops out of the wind and piles up.
- Reduces wind speed at ground level, so the wind can no longer carry the sand away.
- Binds the sand with roots — marram-grass roots hold loose grains together and stabilise the dune.
- Adds humus and nutrients as plants die, letting more species colonise and fix the dune further.
Real coast — Dawlish Warren spit, SW England: Dawlish Warren is a sandy spit and dune system built by longshore drift across the mouth of the Exe estuary in south-west England.
Much of it is left undeveloped: the mobile sand is unstable, the land is low-lying and floods in storm surges, and it is a protected nature reserve — physical reasons a map question asks you to outline.
Changing sea level reshapes whole coasts: When sea level changes relative to the land, a whole coast emerges or drowns.
Emergent coast (sea falls / land rises) → old marine features are stranded above the present sea: raised beaches and relict (abandoned) cliffs.
Submergent coast (sea rises / land sinks) → river or glacial valleys are drowned by the sea: rias (drowned river valleys) and fjords (drowned glacial valleys).
| Landform | Formation sequence |
|---|---|
| Raised beach | Ice age ends -> ice unloads the land -> land slowly rebounds upward (isostatic) -> an old beach is lifted above the present sea as a raised beach, often with a relict cliff behind it |
| Relict cliff | Sea once cut a cliff -> the land rose (or sea fell) -> the cliff is now stranded inland above the active beach, no longer reached by waves |
| Fjord | Glaciers carve a deep, steep U-shaped valley below today's sea level -> the ice melts and sea level rises (eustatic) -> the sea floods the valley to make a deep fjord |
| Ria | A river carves a V-shaped valley -> sea level rises after the ice age -> the lower valley is drowned, giving a winding ria |
How this is tested — the [10] Examine/Evaluate essay: Paper 1 Option B ends with a 10-mark essay, marked on markbands. Recurring versions: the relative roles of wind vs vegetation (or wind vs waves) in coastal landforms, how sea-level change produces relict cliffs / raised beaches / fjords, and how wave processes + lithology create erosional landforms.
Top band needs: accurate terms, two or more developed factors anchored to a named coast, a weighing of their relative importance / interaction, and a clear judgement.