Welcome to Coastal Landscapes and Change!
Hello! In this chapter, we are going to explore the exciting and ever-changing world where the land meets the sea. Coasts aren't just places for holidays; they are dynamic systems—which means they are constantly moving, growing, or shrinking. We will learn how waves, rocks, and even humans shape these landscapes. Don't worry if some of the "geology talk" seems tricky at first; we'll break it down piece by piece!
1. The Coast as a System: The Littoral Zone
Think of the coast not as a thin line on a map, but as a wide zone called the Littoral Zone. This is the area where the land and sea constantly interact.
Breaking down the Littoral Zone:
It’s divided into four main parts:
- Backshore: Usually dry; only affected by waves during massive storms.
- Fore-shore: This is where you walk at the beach! It's the area between high tide and low tide.
- Nearshore: Shallow water where waves start to "break" before hitting the sand.
- Offshore: Deep water where the sea floor isn't really affected by waves.
How we classify coasts:
Geographers group coasts to make them easier to study:
- Rocky Coasts: These have high cliffs and are made of resistant (hard) rock. They are usually found in high-energy environments where the waves are very strong (e.g., North Cornwall).
- Coastal Plain Landscapes: These are low-lying, sandy, or muddy areas. They are found in low-energy environments where the sea is calmer (e.g., East Anglia).
Quick Review: The coast is a system. This means it has inputs (like sediment from rivers), processes (like waves moving sand), and outputs (like sand being washed out to deep sea).
2. Geology: The "Skeleton" of the Coast
The type of rock and how it is "built" (geological structure) determines whether a coast survives or disappears.
Concordant vs. Discordant Coasts
Memory Aid: Think of a striped shirt!
- Discordant Coasts: The "stripes" (rock layers) run perpendicular (at a right angle) to the sea. Because some stripes are soft and some are hard, the sea eats the soft ones faster, creating Headlands and Bays.
- Concordant Coasts: The "stripes" run parallel to the sea. The sea hits one hard layer of rock first, protecting the softer rock behind it. This creates features like Lulworth Cove or Dalmatian-type coasts (long, narrow islands).
The "Dip" of the Rock
The angle at which rock layers sit is called the dip. Analogy: If you lean a deckchair toward the sea, it’s easier to fall off. - If rocks dip seaward (toward the sea), blocks of rock can easily slide down into the water. - If rocks dip landward (away from the sea), the cliff is much more stable.
Key Takeaway: Hard rocks like Igneous (Granite) recede very slowly, while Unconsolidated materials like Boulder Clay (found in Holderness) can disappear by meters every year!
3. Waves: The Engines of Change
Waves are created by wind blowing over the water. The power of a wave depends on the fetch (how far the wind has traveled over the water).
Constructive vs. Destructive Waves
Constructive Waves (The "Builders"): - Low height, long length. - The swash (water moving up the beach) is stronger than the backwash (water pulling back). - Result: They pile up sand and "build" the beach.
Destructive Waves (The "Destroyers"): - High height, short length (they are steep!). - The backwash is much stronger than the swash. - Result: They "steal" sand and erode the beach.
Did you know? A beach can change from "built up" to "stripped bare" in just one day if a storm brings destructive waves!
4. Erosion and Sediment Movement
The sea has four main ways of breaking down the land:
- Hydraulic Action: Air is trapped in rock cracks by a wave and "explodes" under pressure.
- Abrasion: The sea throws pebbles against the cliff like sandpaper.
- Attrition: Pebbles in the sea crash into each other and get smaller and rounder.
- Corrosion (Solution): Sea water dissolves certain types of rock (like limestone).
Longshore Drift: The Coastal Conveyor Belt
This is how sediment moves along the coast. 1. Waves hit the beach at an angle (determined by the wind). 2. The swash carries sand up the beach at that same angle. 3. The backwash pulls the sand straight back down due to gravity. 4. This zig-zag movement carries sand miles down the coast!
Depositional Landforms:
When the sea loses energy, it drops its "luggage" (sediment), creating: - Spits: Long fingers of sand sticking out into the sea (e.g., Spurn Head). - Tombolos: A sandbar that connects the mainland to an island (e.g., Chesil Beach). - Cuspate Forelands: Triangular-shaped headlands (e.g., Dungeness).
Quick Review Box: - Erosion = Taking away. - Transportation = Moving (Longshore Drift). - Deposition = Dropping off.
5. Sea Level Change: Rising and Falling
Sea levels change in two main ways. Students often mix these up, so look closely!
Eustatic vs. Isostatic
- Eustatic (Global): A change in the actual volume of water in the ocean. If ice melts, the sea level rises everywhere. Memory Aid: Eustatic = Everywhere.
- Isostatic (Local): A change in the level of the land. During the Ice Age, heavy ice pushed the land down. Now that the ice is gone, the land is "springing" back up (like a sponge).
Landforms of Sea Level Change:
- Emergent (Sea level fell): Raised beaches—beaches that are now high above the current sea level.
- Submergent (Sea level rose): Rias (flooded river valleys) and Fjords (flooded glacial valleys).
6. Coastal Management: Can We Stop the Sea?
As sea levels rise due to Climate Change, we have to decide how to protect our homes.
Hard Engineering (Man-made, "tough" structures)
- Sea Walls: Concrete walls that reflect wave energy. Very expensive!
- Groynes: Wooden fences built into the sea to stop Longshore Drift. They keep sand on "your" beach but can starve the next beach down the coast.
- Rip-Rap (Rock Armour): Large boulders that soak up wave energy.
Soft Engineering (Working with nature)
- Beach Nourishment: Pumping new sand onto a beach. It looks natural but needs to be done repeatedly.
- Dune Stabilisation: Planting Marram Grass to hold sand dunes together.
The Big Decisions: Shoreline Management Plans (SMPs)
Councils have to choose one of four paths: 1. Hold the Line: Build defenses to keep the coast exactly where it is. 2. Advance the Line: Build new land out into the sea (rare!). 3. Managed Realignment (Strategic Retreat): Let the sea flood certain areas to protect more important ones. 4. No Active Intervention: Do nothing and let nature take its course.
Common Mistake: Thinking everyone wants sea walls. Actually, sea walls are very expensive, and Cost-Benefit Analysis often shows it’s cheaper to let a few houses fall than to spend millions on a wall.
Final Key Takeaways:
1. The coast is shaped by the "battle" between Lithology (rock type) and Marine Processes (waves).
2. Geology is the most important factor in how fast a coast erodes.
3. Sea levels are rising globally, which creates "Environmental Refugees" in low-lying areas like Bangladesh.
4. Coastal management creates winners and losers (conflicts between homeowners and the government).