Caves and Arches: Erosion targets weaknesses in headlands, such as faults or joints, creating a cave. If the erosion continues through to the other side of the headland, an arch is formed, leaving a bridge of rock over the sea.
Stacks and Stumps: As the arch is further weathered and eroded, its roof eventually collapses due to gravity, leaving an isolated pillar of rock called a stack. Over time, the base of the stack is undercut until it collapses, leaving a small, low-lying stump.
Wave-Cut Platforms: As a cliff retreats landward due to undercutting at the base, a flat or gently sloping rocky surface is left behind. This platform is typically visible only at low tide and serves as evidence of the cliff's former position.
Longshore Drift: This is the primary method of sediment transport along a coast, where waves approach the shore at an angle (determined by prevailing winds). The swash moves material up the beach at an angle, while the backwash pulls it straight down, resulting in a zigzag movement of sediment.
Spits and Bars: A spit is an elongated ridge of sand or shingle that extends from the land into the sea, often forming where the coastline changes direction. If a spit grows across a bay to connect two headlands, it becomes a bar, often trapping a lagoon behind it.
Beaches and Tombolos: Beaches are accumulations of sand or shingle in the zone between low and high tides, formed by constructive waves. A tombolo is a specialized feature where a spit or bar connects the mainland to an offshore island.
| Feature | Constructive Waves | Destructive Waves |
|---|---|---|
| Energy Level | Low energy; calm weather | High energy; storm conditions |
| Wave Action | Strong swash, weak backwash | Weak swash, strong backwash |
| Primary Result | Deposition (builds beaches) | Erosion (removes sediment) |
| Profile | Long wavelength, low height | Short wavelength, high height |
Erosion vs. Weathering: Erosion involves the removal and transport of rock by the sea, whereas weathering is the breakdown of rock in situ by atmospheric or biological factors. Both work together to shape coastal cliffs.
Concordant vs. Discordant Coasts: Concordant coastlines have rock layers running parallel to the shore, often resulting in straight coastlines. Discordant coastlines have rock layers at right angles to the sea, leading to the formation of alternating headlands and bays.
Identify the Sequence: When describing erosional landforms, always present them in their chronological order (e.g., crack → cave → arch → stack → stump). This demonstrates an understanding of the progressive nature of coastal evolution.
Process-Landform Link: Never mention a landform without naming the specific processes that created it. For example, link 'spits' to 'longshore drift' and 'hydraulic action' to 'caves'.
Check the Wind Direction: In questions about longshore drift, the direction of sediment transport is always dictated by the prevailing wind. Look for clues in diagrams, such as the angle of incoming wave crests.
Common Mistake: Do not confuse 'abrasion' with 'attrition'. Remember that abrasion is the sea using rocks as tools against the land, while attrition is rocks hitting each other.
