What is the primary difference between constructive and destructive waves?

Constructive waves have a strong swash and weak backwash, leading to deposition and beach building. Destructive waves have a weak swash and a powerful backwash, which removes sediment and causes coastal erosion.

How does a discordant coastline differ from a concordant coastline?

A discordant coastline has rock bands that run perpendicular to the shore, leading to the formation of headlands and bays. A concordant coastline has rock bands parallel to the shore, typically resulting in a straighter coastline.

What is the difference between a spit and a bar?

A spit is a ridge of sand or shingle that extends from the land into the sea, often with a curved end. A bar is formed when a spit grows across a bay, connecting two headlands and trapping a lagoon behind it.

Why is it incorrect to say that attrition erodes a cliff face?

Attrition is the process where rocks and pebbles carried by waves collide with each other, breaking into smaller, smoother pieces. It erodes the sediment itself, not the cliff; abrasion is the process that erodes the cliff face.

What is a common mistake when drawing the process of longshore drift?

Students often draw the backwash at an angle. In reality, while the swash moves up the beach at the angle of the prevailing wind, the backwash always moves straight down the beach (perpendicular to the shore) due to gravity.

Why should weathering not be confused with marine erosion?

Weathering is the breakdown of rock in its original position (in situ) by sub-aerial processes like frost-shattering or chemical decay. Erosion involves the active removal and transport of rock material by the force of the sea.

Define 'Fetch' in the context of coastal geography.

Fetch is the maximum distance of open water over which the wind has blown to create waves. A larger fetch generally results in more powerful, higher-energy waves.

What is 'Hydraulic Action'?

Hydraulic action is an erosional process where the force of waves traps air in cracks in a cliff. The resulting pressure expansion causes the rock to shatter and break away over time.

A tombolo is a depositional landform created when a spit or bar connects the mainland to an offshore island, effectively turning the island into a peninsula.

Explain the process of 'Abrasion'.

Abrasion (or corrasion) occurs when waves pick up sand, pebbles, and boulders and hurl them against the cliff base. This acts like sandpaper, wearing away the rock surface.

Coastal Landforms | OCR GCSE Geography

Distinctive Landscapes

Coastal Landforms

Summary

Coastal landforms are the physical features of the shoreline shaped by the dynamic interaction of marine processes, geology, and climate. These landforms are categorized into erosional features, created by the removal of material, and depositional features, formed by the accumulation of sediment. Understanding these landforms requires analyzing wave energy, sediment transport mechanisms like longshore drift, and the resistance of different rock types.

1. Core Concepts: Wave Dynamics and Energy

Wave Formation: Waves are generated by wind blowing over the sea surface. Their energy is determined by the fetch (the distance the wind has traveled over open water), the wind's strength, and the duration for which the wind blows.
Wave Types: Coastal evolution is driven by two primary wave types. Constructive waves have a strong swash and weak backwash, leading to sediment accumulation and beach building. Destructive waves have a weak swash and powerful backwash, resulting in the removal of material and coastal erosion.
Marine Processes: The coastline is shaped by four main erosional processes: Hydraulic Action (air trapped in cracks by waves), Abrasion (waves flinging sediment against cliffs), Attrition (rocks colliding and breaking into smaller pieces), and Solution (chemical dissolving of soluble rocks like limestone).

2. Erosional Landforms: The Headland Sequence

Headlands and Bays: These form along discordant coastlines where alternating bands of hard and soft rock run perpendicular to the shore. Softer rocks erode faster to form bays, while harder, more resistant rocks remain as protruding headlands.
The Cave-Arch-Stack-Stump Sequence: Erosion targets weaknesses in a headland. Hydraulic action and abrasion enlarge cracks into caves. When caves on opposite sides of a headland meet, they form an arch.
Final Stages: Over time, the roof of an arch becomes too heavy and collapses, leaving an isolated pillar of rock called a stack. Further erosion at the base of the stack causes it to collapse into a small, low-lying stump.
Wave-Cut Platforms: As a cliff retreats due to undercutting at the base (the wave-cut notch), a flat area of rock is left behind at the low-tide mark, known as a wave-cut platform.

Diagram showing the erosional sequence of a headland including a cave, arch, stack, and stump.

3. Depositional Landforms and Transport

4. Key Distinctions: Wave Types and Coastlines

5. Exam Strategy & Tips

6. Common Pitfalls & Misconceptions