Summary
Coastal landforms are shaped by powerful erosion processes such as hydraulic action, abrasion, solution, and attrition. These processes create features like cliffs, wave-cut platforms, headlands, bays, caves, arches, stacks, and stumps over thousands of years.
- Hydraulic Action — Waves compress air in rock cracks, causing explosive expansion that breaks the rock apart. Example: Most powerful during storms, widens existing cracks.
- Abrasion (Corrasion) — Waves hurl sand and pebbles against rock surfaces, wearing them away like sandpaper. Example: Smooths and wears rock surfaces, creates distinctive erosion patterns.
- Solution (Corrosion) — Seawater dissolves certain types of rock, particularly limestone and chalk. Example: Slow but continuous process, affects carbonate rocks.
- Attrition — Rocks and pebbles carried by waves knock against each other, breaking into smaller pieces. Example: Reduces size of beach material, creates sand from pebbles.
- Headland — A promontory of resistant hard rock that juts out into the sea. Example: Formed where hard rock erodes slowly.
- Bay — A curved indentation in the coastline where soft rock has been eroded away. Example: Typically has gently sloping beaches and calmer water.
- Wave-Cut Platform — A gently sloping rocky surface at the base of a cliff. Example: Formed as the cliff retreats landward, visible at low tide.
- Cave — A hollow opening eroded into a cliff base. Example: Formed where waves attack weaknesses like cracks.
- Arch — A natural rock bridge formed when caves on opposite sides of a headland erode through. Example: Sea flows underneath, roof becomes unstable over time.
- Stack — A tall, isolated pillar of rock standing in the sea. Example: Formed when an arch roof collapses.
- Stump — A low piece of rock remaining after a stack has been eroded away. Example: Usually visible only at low tide.
Exam Tips
Key Definitions to Remember
- Hydraulic Action
- Abrasion (Corrasion)
- Differential Erosion
- Headland
- Bay
- Wave-Cut Notch
Common Confusions
- Confusing hydraulic action with abrasion
- Misunderstanding the sequence of cave to stump formation
Typical Exam Questions
- Describe and explain the formation of a wave-cut platform. Include a labeled diagram? Answer: Waves erode the cliff base, creating a wave-cut notch. The cliff collapses, leaving a platform.
- Explain how differential erosion leads to the formation of headlands and bays? Answer: Soft rock erodes faster than hard rock, creating bays and leaving headlands.
- With the aid of diagrams, describe the sequence of erosion from cave to stump? Answer: Waves form caves, which become arches, then stacks, and finally stumps.
What Examiners Usually Test
- Understanding of erosion processes
- Ability to describe the sequence of landform development
- Skill in drawing and labeling diagrams