Coastal landforms — erosion and deposition features

CCEA examines both erosional and depositional coastal landforms. You need to explain the formation of each using correct process terminology, and ideally reference Northern Ireland coastline examples.

Erosional landforms

Cliffs and wave-cut platforms:

• Destructive waves attack the base of a rock face (the wave-cut notch) through hydraulic action and abrasion.
• The rock above the notch eventually collapses under its own weight.
• As the cliff retreats, it leaves behind a wave-cut platform — a gently sloping rock ledge exposed at low tide.

Headlands and bays:

• Where a coastline has alternating bands of resistant (hard) and less resistant (soft) rock, differential erosion occurs.
• Soft rock is eroded more quickly, forming bays; hard rock resists, forming headlands that jut into the sea.
• Once a headland develops, wave energy is concentrated on it (wave refraction) → faster erosion of the headland eventually.

Caves, arches and stacks (the sequence):

1. A cave forms where hydraulic action and abrasion exploit a crack or weakness in a cliff or headland.
2. The cave is enlarged; if erosion on both sides of a headland meets, an arch is formed.
3. The roof of the arch collapses (undermined by erosion and weakened by weathering) → an isolated rock pillar called a stack remains.
4. The stack is further eroded and collapses → a low, flat stump at wave-cut platform level.

NI example: The Old Man of Hoy (Orkney) is a classic stack, but NI has fine examples along the Antrim coast, particularly near the Giant's Causeway (basalt columns create distinctive erosional features).

Depositional landforms

Beaches:

• Built by constructive waves depositing sand and pebbles.
• Sandy beaches: fine sediment deposited in sheltered, low-energy bays.
• Pebble beaches (shingle): coarser material in higher-energy environments.
• NI example: White Rocks Beach (Portrush), Murlough Bay (Mourne coast).

Spits:

• A spit is a narrow ridge of sand or shingle extending from the land into the sea, with one end attached to the land.
• Forms where longshore drift carries sediment past a change in the coastline direction (e.g., an estuary mouth).
• The spit grows in the direction of longshore drift. The end often curves (recurved end) where wave refraction in the shelter of the spit creates a secondary drift.
• Behind the spit: a sheltered lagoon or saltmarsh may develop.

Bars:

• If a spit extends entirely across a bay, it becomes a bar, completely enclosing a lagoon.
• Tombolos: a bar connecting the mainland to an island.

NI Coastal context

The Antrim coast (A2 coastal road) runs along one of Europe's most impressive coastlines. The basalt and chalk geology creates dramatic cliff scenery. The Causeway Coast AONB contains examples of headlands, bays, stacks (Chimney Tops), and beaches within a short distance.