Overview
This lecture explains how waves shape coastlines, focusing on the factors that affect wave size and the differences between constructive and destructive waves.
How Waves Form and Key Characteristics
- Waves are created by wind energy transferred to the sea through friction on the water's surface.
- Waves shape coastlines by causing erosion (wearing away) and deposition (building up).
Factors Affecting Wave Size
- Stronger wind speed transfers more energy, making larger and stronger waves.
- The longer the wind blows, the more energy is transferred to the waves.
- Fetch is the distance wind travels over water; a longer fetch gives waves more energy and size.
- The south-west coast of the UK has bigger waves due to a larger Atlantic fetch compared to the North Sea.
Types of Waves
Constructive Waves
- Swash is stronger than backwash.
- Long wavelength and low wave height.
- Gentle, less frequent waves (6-9 per minute).
- Common in sheltered bays and during summer.
- Build up sandy beaches by depositing material.
Destructive Waves
- Backwash is stronger than swash.
- Short wavelength and high wave height.
- Frequent, powerful waves (10-15 per minute).
- Common in exposed areas and in winter.
- Remove material from beaches, causing erosion.
Key Terms & Definitions
- Crest — the top point of a wave.
- Trough — the lowest point or base of a wave.
- Wave height — vertical distance from trough to crest.
- Wave length — horizontal distance between two crests.
- Wave frequency — number of waves breaking per minute.
- Swash — water movement up the beach after a wave breaks.
- Backwash — water movement back to the sea due to gravity.
- Fetch — the distance wind travels over open water.
Action Items / Next Steps
- Review definitions and features of constructive and destructive waves.
- Be prepared to explain how wind and fetch affect wave size.
- Learn how wave type influences coastal erosion and deposition.