Coasts: Erosion and Deposition Landforms, Coral Reefs and Coastal Management

This guide covers 2.3, Coasts, from Theme 2, The Natural Environment, in Cambridge IGCSE Geography 0460. It follows Rivers and applies the same erosion/transportation/deposition framework to coastal, rather than river, environments.

The work of the sea and wind

You need to demonstrate understanding of the work of the sea and wind in eroding, transporting and depositing material along a coastline, and to describe and explain the formation of the landforms these processes create.

Erosion is the wearing away and removal of rock and sediment by a moving agent – here, waves and currents. It is distinct from weathering, the breakdown of rock where it stands, with no movement involved (for example, salt crystallisation or freeze-thaw action weakening a cliff face); weathering often prepares rock for erosion to then remove, and exam answers that treat the two as interchangeable lose marks. Four processes of wave erosion are commonly taught: hydraulic action (the sheer force of moving water, compressing air trapped in cracks and joints in the rock until it weakens and breaks apart), abrasion (also called corrasion – sediment carried by waves is thrown against the coastline, wearing it away), attrition (sediment being carried collides with other sediment, breaking it down into smaller, more rounded fragments over time), and solution (also called corrosion – mildly acidic seawater chemically dissolves soluble rock such as limestone or chalk).

Sediment is then moved by the same four transport processes used for rivers: traction (large, heavy material rolled along the seabed), saltation (smaller material bounced along the seabed), suspension (fine material carried within the moving water), and solution (dissolved material carried in the water itself, invisibly).

Whether a stretch of coastline is dominated by erosion or by deposition depends heavily on wave type. Constructive waves are low-energy, with a long wavelength and a low frequency; their swash (the rush of water up the beach) is stronger than their backwash (the water draining back down), so they build up and add material to a beach. Destructive waves are high-energy, steeper, with a short wavelength and a high frequency; their backwash is stronger than their swash, so they remove material from a beach and drive the erosional landforms below.

Erosional landforms

You need to know a named set of coastal erosional landforms: cliffs, wave-cut platforms, caves, arches, stacks, stumps, and bay and headland coastlines. These landforms form a recognisable developmental sequence worth learning in order: wave action erodes a line of weakness in a cliff to form a cave; continued erosion may cut through a headland entirely to leave an arch; the arch’s roof eventually collapses, leaving an isolated pillar of rock, a stack, separated from the cliff; further erosion reduces the stack to a low, worn remnant, a stump. Alongside this sequence, a wave-cut platform forms at the base of an eroding cliff as the cliff retreats, leaving a gently sloping rock surface exposed at low tide. Bay and headland coastlines develop where a coastline alternates between bands of softer rock (eroded faster, forming bays) and harder rock (eroded more slowly, remaining as headlands).

Depositional landforms

You need to know beaches, spits, and coastal sand dunes as depositional landforms. A beach forms where wave energy is insufficient to remove all the sediment being deposited, building up a store of sand or shingle along the shoreline. A spit forms where longshore drift (the movement of sediment along a coast, driven by waves approaching at an angle) carries material past a bend in the coastline, where the coastline changes direction and deposition continues out into open water, building a narrow, extending ridge of sediment. Coastal sand dunes form further inland from the beach itself, where wind transports and deposits dry sand, often becoming stabilised over time by colonising vegetation.

Coral reefs and mangrove swamps

You need to describe coral reefs and mangrove swamps, and the specific conditions required for their development. Coral reefs require warm, clear, shallow, and typically nutrient-poor water, since coral-building organisms are sensitive to temperature and depend on sunlight penetrating the water for the photosynthetic algae living within them. Mangrove swamps require warm temperatures and sheltered, low-energy coastal conditions – typically estuaries or lagoons – where fine sediment can settle and salt-tolerant mangrove vegetation can establish itself.

Hazards, opportunities and coastal management

You need to demonstrate understanding that coasts present both hazards and opportunities for people, with hazards specifically including coastal erosion and tropical storms, and you need to explain what can be done to manage the impacts of coastal erosion. As with rivers, coastal management approaches range from hard engineering (such as sea walls or groynes, which trap sediment moving via longshore drift to help maintain a beach) to softer approaches that work with natural processes rather than resisting them directly.

Required case study

The syllabus specifies one case study is required for 2.3: the opportunities presented by an area or areas of coastline, the associated hazards, and their management. As with the case studies required in 2.1 and 2.2, prepare specific, named detail rather than generic coastal description.

A worked example: longshore drift and spit formation

Waves rarely approach a coastline exactly head-on; when they arrive at an angle, the swash (water moving up the beach) carries sediment diagonally up the beach in the direction of the wave, while the backwash (water draining back down) is pulled by gravity straight back down the steepest slope. Repeated over many wave cycles, this zig-zag movement – longshore drift – gradually transports sediment along the coast in the dominant direction the waves approach from. Where the coastline changes direction, such as at a river mouth or bay, this moving sediment continues in roughly the same direction into open water rather than following the new coastline angle, gradually building a narrow ridge of deposited material: a spit. Over time, spits can grow long enough to partially or fully enclose a body of water behind them, sometimes developing a curved or hooked end where wave patterns or a river current alter the direction sediment is being carried. Explaining spit formation this way – as a direct consequence of longshore drift meeting a change in coastline direction – is a frequently tested example of applying process to landform.

How to approach it

Learn the erosional landform sequence (cave, arch, stack, stump) together as a single process rather than four separate definitions, since exam questions often ask you to explain the sequence of formation, not just identify a labelled diagram. Keep erosional and depositional landforms in two clearly separated groups when revising – cliffs, wave-cut platforms, caves, arches, stacks, stumps and headlands on the erosion side; beaches, spits and dunes on the deposition side – since confusing which process produced a given landform is a common source of lost marks. For coral reefs and mangrove swamps, learn the specific environmental conditions each requires (warm, clear, shallow water for reefs; sheltered, low-energy, sediment-rich conditions for mangroves) as the actual explanatory content, since “describe” command words in this part of the syllabus still expect the underlying conditions to be stated, not just the ecosystem named.

A note on the syllabus successor

This guide is written against the 2025-2026 series of Cambridge IGCSE Geography 0460, cited below. Only the November 2026 series still sits on that syllabus. A successor syllabus for the 2027-2029 series has already been published and restructures the qualification significantly: the three themes become ten topics (so the “Theme 2” numbering used throughout this guide will not carry over), the first two papers are renamed and reweighted from Themes and Skills to Physical and Human Geography at 36% each, and the alternative-to- coursework paper is also renamed. This guide has not yet been re-based onto the successor syllabus.

Official syllabus

Cambridge International, Cambridge IGCSE Geography (0460) syllabus for 2025 and 2026: official syllabus PDF, Subject content, section 2.3 “Coasts”. Verified 2026-09-02. Successor: Cambridge IGCSE Geography (0460) syllabus for 2027-2029.