Coasts (Autumn, first half)

Topic 1: The coast and the wider littoral zone have distinctive features and landscapes

Key ideas

• The littoral zone is the wider coastal zone. It runs from the backshore (above the high-tide mark, affected only by storm waves), through the foreshore/nearshore (the intertidal zone and the shallow water where waves break), to the offshore zone (beyond the breaker zone, where waves have little effect on the sea bed).
• The coast is a dynamic zone of rapid change because energy (waves, tides, wind, currents) and sediment inputs vary on timescales from hours to millennia.
• The coast works as an open system:
  • Inputs: energy from waves, tides and wind; sediment from rivers, cliffs and the sea bed.
  • Stores: beaches, dunes and offshore bars.
  • Outputs: sediment carried offshore or alongshore.
• Dynamic equilibrium means the system adjusts its form (for example, beach profile) to balance changing inputs and outputs.
• Coasts can be classified in several ways:
  • Longer-term criteria:
    • Geology – rocky compared with sandy coasts; concordant compared with discordant coasts.
    • Sea-level change – emergent coasts (land has risen relative to the sea) compared with submergent coasts (the sea has risen relative to the land).
  • Shorter-term process criteria:
    • Energy: high-energy coasts have large waves, long fetch and erosion dominating. Low-energy coasts have small waves, sheltered bays and deposition dominating.
    • Tidal range: micro-tidal (<2 m), meso-tidal (2–4 m) or macro-tidal (>4 m).
    • Inputs from rivers – estuarine and deltaic coasts.
  • Primary compared with secondary coasts (Shepard's classification): primary coasts are shaped mainly by land-based processes (e.g. rias, deltas); secondary coasts are shaped mainly by marine processes (e.g. cliffed coasts, barrier beaches).
• Rocky coasts:
  • High-relief rocky coasts have cliffs over about 10 m high (e.g. Land's End).
  • Low-relief rocky coasts have low cliffs or shore platforms.
  • They form on resistant geology, usually in high-energy environments.
• Coastal plains (sandy and estuarine coasts) form in areas of low relief. They are fed by sediment from rivers, offshore sources and longshore drift, usually in low-energy environments (e.g. the Holderness and Lincolnshire coastal plain, the Wadden Sea, the Ganges–Brahmaputra delta).

Glossary

Term	Definition
Littoral zone	The coastal zone, from the land affected by sea spray and storm waves out to the offshore zone.
Backshore	Above the normal high-tide mark; reached only by storm waves.
Nearshore / foreshore	The intertidal and shallow area where waves break and most sediment is moved.
Offshore	Deeper water beyond the breaker zone.
Dynamic equilibrium	A system that keeps a balance by constantly adjusting to changing inputs.
Emergent coast	A coast where the land has risen relative to the sea (e.g. through isostatic rebound).
Submergent coast	A coast flooded by a relative rise in sea level.
High-energy coast	A coast with powerful waves (long fetch, exposed); erosion exceeds deposition.
Low-energy coast	A sheltered coast with small waves; deposition exceeds erosion.
Fetch	The distance of open water over which wind blows to generate waves.
Tidal range	The vertical difference between high and low tide.
Sediment budget	The balance between sediment inputs and outputs in a stretch of coast.

Key facts and processes

• Wave energy depends on wind speed, wind duration and fetch. The formula is P ∝ H²T (wave power is proportional to the square of wave height multiplied by wave period), so doubling wave height roughly quadruples wave energy.
• Example of a long fetch: the south-west coast of the UK faces the Atlantic, with a fetch of several thousand kilometres, so it receives high-energy swell waves.

Case-study pointers

Coast	Type	Key point
Cornwall (e.g. Land's End)	High-energy, high-relief rocky coast	Resistant granite; Atlantic fetch.
Holderness, East Yorkshire	Low-relief cliffed coast of weak boulder clay	Rapid erosion (see Topic 3).
Ganges–Brahmaputra delta (Bangladesh)	Low-energy coastal plain fed by huge river sediment loads	Vulnerable to flooding.

Exam technique

• An 8-mark question here might be "Explain why some coasts are high-energy and others low-energy."
• Organise it by the factors: fetch and wind → wave type → geology/relief → resulting landscape.
• Give a named UK example and a non-UK example.

Self-test

Q1: Name the three parts of the littoral zone. A: Backshore, nearshore (foreshore) and offshore.

Q2: Give two longer-term and two shorter-term ways of classifying coasts. A: Longer-term: geology (rocky/sandy; concordant/discordant) and sea-level change (emergent/submergent). Shorter-term: wave energy (high/low) and tidal range, or river input.

Q3: Why are rocky coasts usually high-energy? A: They are often exposed to long fetches and deep water close inshore, so large waves reach the shore without losing much energy. Resistant rock means steep, cliffed profiles persist under this energy.

Q4: What is dynamic equilibrium? A: A state of balance in a system that is maintained by continual adjustment to changing inputs. For example, a beach profile flattens in winter storms and steepens in summer.

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Topic 2: Geological structure influences coastal landscapes at a variety of scales

Key ideas

• Geological structure means the arrangement of rocks: strata (layers), bedding planes, joints, faults, folding and dip (the angle at which the strata tilt).
• Concordant coasts: bands of rock run parallel to the coastline.
  • Dalmatian coast: parallel ridges and valleys that have been drowned by sea-level rise, leaving long islands parallel to the shore (e.g. the Dalmatian coast of Croatia).
  • Haff coast: long sand spits (Nehrungen) enclose lagoons (Haffs) parallel to the coast (e.g. the southern Baltic, such as the Curonian Spit in Lithuania/Russia).
  • Lulworth Cove (Dorset): the sea broke through resistant Portland limestone and eroded the weaker Wealden clays and sands behind, forming a near-circular cove. It is backed by the more resistant Chalk.
• Discordant coasts: bands of rock run perpendicular to the coastline, so they erode at different rates.
  • Weaker rocks are eroded into bays; resistant rocks are left as headlands.
  • Example: Swanage Bay (weak Wealden clays) lies between Durlston Head (Portland/Purbeck limestone) and Ballard Point/Old Harry (Chalk), on the Isle of Purbeck, Dorset.
  • Headlands refract wave energy onto themselves; bays receive diverging, weaker waves and become sites of deposition.
• Micro-features and cliff profiles:
  • Joints, faults and bedding planes are lines of weakness exploited by hydraulic action, so they form caves, geos and blowholes.
  • Dip controls the cliff profile:
    • Strata dipping landward (or horizontal) give steep, stable cliffs.
    • Strata dipping seaward give lower-angle cliffs with blocks prone to sliding down the bedding planes.
  • Example: the Glamorgan Heritage Coast (south Wales) has horizontally bedded Jurassic limestone and shale (Lias). The cliffs are near-vertical and stepped, with a wide wave-cut platform and frequent rockfalls.

Glossary

Term	Definition
Concordant coast	A coast where rock bands run parallel to the shoreline.
Discordant coast	A coast where rock bands run at right angles to the shoreline; forms headlands and bays.
Dalmatian coast	A concordant coast of drowned parallel ridges forming elongated islands.
Haff coast	A concordant coast with long sand spits enclosing lagoons.
Joint	A crack in rock with no displacement, often formed by cooling or pressure release.
Fault	A fracture along which rocks have been displaced.
Bedding plane	The boundary between sedimentary layers.
Dip	The angle of tilt of rock strata.
Wave refraction	The bending of wave fronts as they approach an irregular coast, which concentrates energy on headlands.

Exam technique

• A 6-mark resource question might show a photo of a cove or headland.
• Name the structural features you can see (e.g. "the strata dip seaward").
• Link each feature to a process (e.g. "so blocks slide along the bedding planes into the sea").

Self-test

Q1: Distinguish between concordant and discordant coasts. A: On concordant coasts the rock bands run parallel to the coast, giving relatively straight coasts, coves, and Dalmatian or Haff types. On discordant coasts the rock bands run perpendicular to the coast, so differential erosion forms headlands and bays.

Q2: How does dip affect cliff profile? A: Seaward-dipping strata produce lower-angle cliffs with sliding along the bedding planes. Landward-dipping or horizontal strata produce steep, sometimes stepped cliffs.

Q3: Explain the formation of Lulworth Cove. A: Waves eroded through a gap in the resistant Portland limestone. The weaker clays and sands behind were eroded rapidly, widening the cove. The more resistant Chalk at the back limits further erosion, and wave refraction through the narrow entrance produces the circular shape.

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Topic 3: Rates of coastal recession and stability depend on lithology and other factors

Key ideas

• Lithology means the physical and chemical character of rock. It strongly controls recession rates.

Rock type	Examples	Typical recession rate	Why
Igneous	Granite, basalt	Very slow (<1 mm/yr)	Interlocking crystals; few joints; chemically resistant.
Metamorphic	Slate, schist	Slow (1–10 mm/yr)	Crystalline, but foliation creates weaknesses.
Sedimentary	Chalk, limestone, sandstone	Moderate to fast (mm to cm per year, sometimes more)	Bedding planes and joints; some are soluble (limestone, chalk).
Unconsolidated	Boulder clay (glacial till), sands	Very fast (often metres per year)	Loose and weak; slumps when saturated.

• Differential erosion happens where cliffs have alternating strata that differ in resistance (hard/soft) or permeability (permeable/impermeable):
  • The softer layers are eroded back, undercutting the harder layers above.
  • Water percolating through permeable rock builds up pore pressure at an impermeable layer (e.g. sandstone over clay), which triggers slumping.
  • Example: the cliffs at Barton-on-Sea (Hampshire), where permeable sands over clay cause rotational slumping.
• Vegetation stabilises sandy and estuarine coasts through succession.
• Sand dune succession (psammosere):
  1. Embryo dunes: pioneer plants such as sea couch grass and lyme grass tolerate salt and trap sand.
  2. Fore/yellow dunes: marram grass grows upward through burial and its roots bind sand; the dunes look yellow because of bare sand.
  3. Grey dunes: humus darkens the soil and plants such as heather and mosses appear.
  4. Dune slacks: damp hollows where the water table reaches the surface.
  5. Mature dunes: heath or woodland climax (e.g. pine and birch).
• Salt-marsh succession (halosere):
  1. Mudflats are colonised by algae and eelgrass.
  2. Pioneers such as Spartina (cord-grass) and Salicornia (glasswort) trap silt and raise the marsh surface.
  3. Plants that are less salt-tolerant follow (e.g. sea lavender and sea purslane).
  4. The upper marsh develops rushes, then scrub.
• Salt marshes and dunes absorb wave energy and act as natural sea defences.

Glossary

Term	Definition
Lithology	The physical and chemical composition of rocks.
Unconsolidated material	Loose sediment that is not cemented into rock, e.g. boulder clay or sand.
Boulder clay (till)	Unsorted glacial deposit of clay with stones; very weak when wet.
Differential erosion	Different rates of erosion on rocks of different resistance.
Succession	The sequence of plant communities colonising a new surface over time.
Psammosere / Halosere	Plant succession on sand / in salt water (salt marsh).
Pioneer species	The first plants to colonise; tolerant of harsh conditions.
Climax community	The final, stable vegetation community.

Case study: the Holderness coast, East Yorkshire (fast recession on weak lithology)

• Length and geology: about 60 km of cliffs south of Bridlington (Flamborough Head to Spurn Head). The cliffs are composed mainly of glacial till (boulder clay) and reach about 40 m high at Dimlington.
• Rate of erosion:
  • Average erosion is around 1.8 m per year. East Riding of Yorkshire Council's monitoring calculated 1.82 m/yr from Sewerby to Spurn, with long-term averages of about 1.2–2.7 m/yr.
  • Rates vary locally: from almost zero just south of Bridlington to over 4 m/yr south of Withernsea (4.32 m/yr at Holmpton in the council's 2012 data).
  • It is often described as one of the fastest-eroding coastlines in Europe.
• Why it is so fast:
  • Soft, unconsolidated till.
  • Narrow beaches that offer little protection.
  • Exposure to North Sea storm waves from the north-east.
  • Slumping when the clay is saturated.
  • Erosion is episodic: a single failure can remove about 16 m, followed by several quiet years.
• Hard rock contrast: Flamborough Head at the northern end is chalk. It erodes much more slowly and forms headlands, caves, arches and stacks.

Exam technique

• For "Explain why rates of recession vary" (8 marks), structure the answer: lithology → structure → vegetation → marine factors (fetch, beach width) → human factors.
• Use the Holderness and Flamborough contrast as a perfect "same coast, different rock" example.

Self-test

Q1: Rank granite, chalk and boulder clay by resistance and explain. A: Granite (most resistant: crystalline, few joints) > chalk (jointed, soluble, moderately resistant) > boulder clay (least resistant: unconsolidated and weak when saturated).

Q2: What is Holderness's average erosion rate and why is it high? A: About 1.8 m/yr on average (locally over 4 m/yr). The cliffs are made of unconsolidated boulder clay, the beaches are narrow, the coast is exposed to North Sea storm waves, and the saturated clay slumps.

Q3: Explain how marram grass stabilises dunes. A: It tolerates burial and grows upwards through accumulating sand. Its long roots and rhizomes bind the sand, and its leaves reduce wind speed at the surface, encouraging deposition.

Q4: Name two pioneer species of salt marsh. A: Spartina (cord-grass) and Salicornia (glasswort). Eelgrass and algae also colonise mudflats.

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Topic 4: Marine erosion creates distinctive coastal landforms and landscapes

Key ideas

• Wave types:

	Constructive waves	Destructive waves
Height and frequency	Low (<1 m); 6–8 per minute	High; 10–14 per minute
Swash/backwash	Strong swash, weak backwash	Weak swash, strong backwash
Effect on beach	Builds up the beach, forms berms; gentle profile in summer	Removes sediment offshore (forms offshore bars); steep, then flattened winter profile
Typical conditions	Distant storms, calm local weather	Local storms, short fetch

• Beach profiles change over time:
  • Daily, with tides and individual storms.
  • Seasonally: the steeper summer berm is cut back in winter.
  • Over the longer term, with changes in sediment supply and sea level.
• Erosion processes:
  • Hydraulic action: waves compress air in cracks, and the pressure release widens the cracks. This includes wave quarrying.
  • Abrasion (corrasion): the sea throws sediment against the cliff and grinds it.
  • Attrition: particles collide and become smaller and rounder.
  • Corrosion (solution): chemical dissolution, especially of limestone and chalk by weak acids.
• Erosion is greatest with high, steep, destructive waves, when waves break at the cliff foot, during storms and at high tide, and where the rock is jointed or weak.
• Landforms of erosion:
  • Wave-cut notch and platform:
    1. Erosion is concentrated between high and low tide, forming a notch.
    2. The overhang collapses and the cliff retreats.
    3. A gently sloping platform (usually less than 4°) is left behind.
    4. As the platform widens, it dissipates wave energy, which is a negative feedback.
  • Cliffs: steep faces shaped by erosion at the base and subaerial processes on the face.
  • Cave → arch → stack → stump:
    1. Weaknesses (joints/faults) in a headland are eroded by hydraulic action and abrasion into a cave.
    2. Caves on either side meet to form an arch (e.g. Durdle Door, Dorset).
    3. The arch roof collapses, leaving a stack (e.g. Old Harry, Dorset).
    4. The stack is eroded into a stump (e.g. Old Harry's Wife).
  • Other erosional features: geos and blowholes.

Glossary

Term	Definition
Swash / backwash	The movement of water up / down the beach after a wave breaks.
Berm	A ridge of sand or shingle at the high-water mark built by constructive waves.
Hydraulic action	Erosion by the force of water and compressed air in cracks.
Abrasion (corrasion)	Erosion by sediment being thrown against rock.
Attrition	Rock fragments colliding and becoming smaller and rounder.
Corrosion (solution)	Chemical dissolution of rock by seawater.
Wave-cut platform	A gently sloping rocky surface left behind as cliffs retreat.
Negative feedback	A change that reduces the original effect, e.g. a wider platform reduces erosion.

Exam technique

• An 8-mark question here might be "Explain the formation of a cave–arch–stack–stump sequence."
• Write it as a numbered process.
• Name the erosion processes at each stage and link them to the geology (joints, faults).
• Give a named example for each stage.

Self-test

Q1: Give three differences between constructive and destructive waves. A: Constructive waves are low with a strong swash, a weak backwash and a low frequency (6–8 per minute), and they build beaches. Destructive waves are high with a weak swash, a strong backwash and a high frequency (10–14 per minute), and they remove sediment.

Q2: Why does a wave-cut platform limit further erosion? A: As it widens, waves break further offshore and lose energy crossing the platform. This is negative feedback, so less energy reaches the cliff foot.

Q3: Name a UK arch and a UK stack. A: Durdle Door (arch, Dorset); Old Harry (stack, Dorset).

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Topic 5: Sediment transport and deposition create distinctive landforms

Key ideas

• Transport processes:
  • Traction: large particles roll along the sea bed.
  • Saltation: particles bounce along.
  • Suspension: fine particles are carried within the water.
  • Solution: dissolved material.
• Longshore drift (LSD): waves approach at an angle set by the prevailing wind. Swash moves sediment up the beach at that angle, and backwash returns it straight down under gravity, so sediment zig-zags along the coast. Tides and currents (e.g. rip currents) also move sediment.
• Deposition occurs when energy falls, for example in sheltered bays, where the coastline changes direction, behind obstacles, where rivers meet the sea, or through flocculation of clay particles in salty water.
• Depositional landforms:

Landform	Formation	Example
Beach	Accumulation between low tide and the highest storm waves. Sand beaches are gentle; shingle beaches are steep because the coarse material allows percolation of backwash.	Chesil Beach (shingle)
Spit	LSD carries sediment past a change in coastline direction; it builds out into open water. The end curves (recurved) through wave refraction and secondary winds. Salt marsh forms behind it.	Spurn Head (Holderness); Hurst Castle Spit (Hampshire)
Double spit	Two spits grow towards each other from opposite sides of an inlet.	Poole Harbour entrance (Studland and Sandbanks)
Bar / barrier beach	A spit grows across a bay and closes it off, forming a lagoon behind.	Slapton Sands (Devon), enclosing Slapton Ley
Offshore bar	Sand deposited offshore by destructive waves' backwash.	Common on many beaches in winter
Tombolo	A beach linking an island to the mainland.	Chesil Beach linking the Isle of Portland; St Ninian's (Shetland)
Cuspate foreland	A triangular projection formed where LSD from two directions meets.	Dungeness (Kent)

• Sediment cells (littoral cells) are largely closed stretches of coast (sources → transfers → sinks).
  • England and Wales are divided into 11 major cells, which are divided into sub-cells.
  • Example: Portland Bill to Selsey Bill (Cell 5).
    • Sources: eroding cliffs (e.g. the chalk and soft Tertiary rocks of the Dorset and Hampshire coasts) and rivers.
    • Transfers: easterly LSD.
    • Sinks: Hurst Castle Spit, Chesil Beach and offshore banks.
• Cells operate in dynamic equilibrium with feedback:
  • Negative feedback restores balance. For example, storm erosion of a beach builds an offshore bar, which then makes waves break earlier and protects the beach.
  • Positive feedback amplifies change. For example, groynes trap sediment updrift, starving the downdrift beach, which then erodes faster, which lowers the beach further.
• Plant succession (see Topic 3) stabilises spits, bars and tombolos.

Glossary

Term	Definition
Longshore drift	Movement of sediment along the coast by oblique swash and perpendicular backwash.
Sediment cell	A stretch of coast, largely self-contained for sediment movement.
Source / transfer / sink	Origin of sediment / zone of movement / area of deposition.
Spit	A long, narrow ridge of sediment attached to land at one end.
Tombolo	A ridge of sediment joining an island to the mainland.
Cuspate foreland	A triangular depositional feature formed by convergent LSD.
Flocculation	Clumping of fine clay particles in salt water, which makes them settle.
Positive feedback	A change that amplifies the original effect.

Exam technique

• A 12-mark question here might be "Assess the importance of sediment supply in the formation of depositional landforms."
• Weigh sediment supply against other factors: wave energy/LSD, coastline shape, sheltering, vegetation and sea-level change.
• Judge which factor matters most, e.g. "Sediment supply is a necessary condition, but…".

Self-test

Q1: Explain longshore drift. A: Prevailing wind drives waves obliquely onto the beach. The swash carries sediment up the beach at an angle, and the backwash drags it straight back down by gravity, so sediment moves in a zig-zag along the shore.

Q2: What is a cuspate foreland? Give an example. A: A triangular depositional feature formed where two LSD directions converge. Example: Dungeness, Kent.

Q3: Give an example of positive feedback in a sediment cell. A: Groynes trap sediment updrift, starving downdrift beaches. Narrower beaches let waves attack the cliffs, which increases erosion and lowers the beach further.

Q4: Name the sediment cell running from Portland Bill to Selsey Bill and one sink within it. A: Cell 5 of the English and Welsh coast. Sinks include Hurst Castle Spit and Chesil Beach.

Assessment checkpoint (first half-term): a Coasts 8-mark "Explain" question and a short-question paper including a waves source. Revise Topics 1–5 and practise 3/6-mark resource questions on wave data, for example calculating the mean wave frequency and classifying it as constructive or destructive.

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