Wave action:
o Constructive waves: build up the beach; low energy; strong swash,
weak backwash.
o Destructive waves: erode the coast; high energy; strong backwash,
weak swash.
Erosion (wearing away of coastal rock):
o Hydraulic action: a force of waves compresses air in cracks.
o Abrasion (Corrosion): Rocks hurled by waves scrape the coastline.
o Attrition: rocks collide, breaking into smaller, smoother pieces.
o Solution (Corrosion): acidic seawater dissolves soluble rocks like
chalk or limestone.
Transportation:
o Longshore drift: sediment movement along the coast due to an
angled wave approach.
o Traction: large particles rolled along the seafloor.
o Saltation: small pebbles bounce along.
o Suspension: light material carried within the water.
o Solution: dissolved materials carried in water.
Deposition: occurs when wave energy drops, depositing material.
Weathering
Mechanical:
o Freeze-thaw weathering – water enters cracks, freezes, expands,
and breaks rock apart.
Chemical:
o Acid rain or sea spray reacts with minerals (e.g. carbonation on
limestone).
Biological:
o Plant roots grow in cracks or animals burrow, breaking down the
rock.
Mass Movement
Sliding: material moves in a straight line down a slope.
Slumping: saturated soil and weak rock rotate and slump downhill.
b) Influence on Coastal Environments
Geology:
o Hard rock (granite) erodes slowly → headlands, cliffs.
o Soft rock (clay, sandstone) erodes quickly → bays, gentle slopes.
Vegetation:
o Stabilises dunes and salt marshes.
o Helps trap sediment and reduce erosion.
Human Activity:
o Coastal defences, tourism, and urbanisation alter natural processes.
o Dredging or building disrupts sediment transport.
Sea-Level Change:
o Eustatic change: global rise/fall due to melting ice or thermal
expansion.
o Isostatic change: local rise/fall due to land movement (e.g., post-
glacial rebound).
c) Erosional and Depositional Landforms
Erosional Landforms
Headlands and Bays: differential erosion of hard and soft rock.
Cliffs and Wave-cut Platforms: erosion at the base causes cliff collapse,
leaving a flat platform.
Caves → Arches → Stacks → Stumps:
o Caves form in headlands.
o Erosion breaks through, forming an arch.
o The arch collapses, leaving a stack.
o The stack erodes into a stump.
Depositional Landforms
Beaches: formed by the deposition of sediment by constructive waves.
Spits: long, narrow ridges of sand/shingle connected to land at one end,
formed by longshore drift.
Bars: spit that grows across a bay, joining two headlands.
2.2 Distinctive ecosystems develop along particular stretches of
coastline
a) Distributions and Features of the World’s Coastal Ecosystems
Coral Reefs:
o Found in tropical shallow seas (23.5° N/S of the equator).
o Require warm, clear, salty water.
o High biodiversity, vulnerable to bleaching.
Mangroves:
o Found in tropical/intertidal zones.
o Salt-tolerant trees with aerial roots.
o Buffer coastlines from erosion and storms.
Sand Dunes:
o Found behind beaches.
o Formed by wind-blown sand trapped by vegetation.
o Plant succession (e.g. marram grass stabilises dunes).
Salt Marshes:
o Form in sheltered estuaries behind spits.
o Saline, waterlogged environments with halophytic plants.
o Important breeding grounds for birds.
b) Abiotic and Biotic Characteristics of One Named Coastal Ecosystem
Example: Keyhaven Salt Marsh (Hampshire, UK)
Abiotic factors:
o Saline water, low oxygen soil, tidal inundation.
o Sheltered location with fine sediment deposition.
Biotic factors:
o Plant species: glasswort, sea lavender.
o Animal species: wading birds, salt marsh beetles.
o Plant succession from mudflats → pioneer plants → higher marsh.
c) Threats to Coastal Ecosystems
Small-scale threats:
o Local tourism leads to trampling, littering, and erosion.
o Small-scale farming/agriculture leads to runoff (pollution,
eutrophication).
Large-scale threats:
o Industrialisation pollutes water and disrupts habitats.
o Agriculture: land drainage, fertiliser use damages ecosystems.
o Deforestation: especially for mangroves – loss of biodiversity and
natural protection.
o Tourism development: construction destroys habitats (e.g. coral
reefs dredged for hotels).
o Climate change: rising sea levels flood habitats; warmer oceans
bleach coral reefs.
