Coastal landscape development

Welcome to Coastal Landscape Development!

In this chapter, we are going to explore how the coast is shaped over time. Think of the coastline as a dynamic battlefield where the land and the sea are constantly fighting for space. Sometimes the sea wins (erosion), and sometimes the land gains ground (deposition). By the end of these notes, you’ll understand how everything from massive cliffs to tiny sand dunes is formed, and how changing sea levels have completely reshaped our world over the last 10,000 years.

Don't worry if some of the terms seem a bit "geography-heavy" at first. We’ll break them down step-by-step with simple analogies to help them stick!

1. Landscapes of Coastal Erosion

Erosion happens when the energy of the waves wears away the land. This creates some of the most dramatic scenery in the UK and abroad.

Cliffs and Wave-Cut Platforms

How does a giant cliff "move" backward? It’s a process called cliff retreat. It happens in three main steps:

1. The sea attacks the base of the cliff between the high and low tide marks. This creates a wave-cut notch (a little "dent" at the bottom).
2. As the notch gets deeper, the cliff above it becomes unstable because there is nothing supporting it. It eventually collapses.
3. This process repeats. The cliff moves back (retreats), leaving behind a flat, rocky area called a wave-cut platform that is visible at low tide.

Caves, Arches, Stacks, and Stumps

This is a classic sequence that examiners love! Think of it as a life cycle of a headland:

• Caves: Waves find a weakness (like a crack or fault) in a headland and widen it through hydraulic action and abrasion.
• Arches: The cave is eroded all the way through to the other side of the headland.
• Stacks: The roof of the arch becomes too heavy and collapses, leaving an isolated pillar of rock standing in the sea.
• Stumps: The stack is eroded at the base until it collapses, leaving a small nub of rock usually only visible at low tide.

Quick Review Box:
Wave-cut notch -> Cliff collapse -> Retreat -> Wave-cut platform.
Crack -> Cave -> Arch -> Stack -> Stump.

Key Takeaway: Erosional landforms are created by high-energy waves (destructive waves) and are influenced by the type of rock (geology) and the presence of weaknesses like faults.

2. Landscapes of Coastal Deposition

Deposition happens when the sea "runs out of breath." When waves lose energy, they drop the material (sand, pebbles, silt) they were carrying. This material is called sediment.

Beaches

Beaches are the most common depositional landform. They are found in low-energy environments like bays. Constructive waves build them up by having a strong swash (pushing sand up) and a weak backwash (not pulling much back out).

Spits and Tombolos

These features are created by Longshore Drift (LSD). Imagine LSD as a conveyor belt moving sand along the coast.

• Spits: A long, narrow ridge of sand or shingle that sticks out into the sea. It forms where the coastline suddenly changes direction. The end often curves (a hooked end) because of changes in wind direction.
• Tombolos: This is simply a spit that has grown so long it connects the mainland to an island! Example: Chesil Beach in Dorset connects the Isle of Portland to the mainland.

Offshore Bars and Barrier Beaches

• Offshore Bars: Ridges of sand submerged just offshore, created when waves break before reaching the beach and drop their sediment.
• Barrier Beaches/Islands: If a bar is pushed toward the land or grows high enough to stay above the water, it becomes a barrier beach, often creating a lagoon behind it.

Sand Dunes

Dunes are formed when the wind blows sand inland. They aren't just piles of sand; they follow a process called succession:

1. Embryo Dunes: Small bumps of sand trapped by things like driftwood.
2. Yellow Dunes: Hardy "pioneer" plants like Marram Grass grow. Their long roots bind the sand together.
3. Grey Dunes: As plants die, they add nutrients to the soil, allowing more complex plants to grow.

Did you know? Marram grass is the "superhero" of the sand dunes. It can survive being buried by sand and "drinks" salt water!

Key Takeaway: Depositional landforms need a constant supply of sediment and low-energy conditions to grow.

3. Estuaries: Mudflats and Saltmarshes

Estuaries are where rivers meet the sea. Because the water is very still here, even tiny particles of mud and silt can settle.

• Mudflats: Flat areas of mud exposed at low tide.
• Saltmarshes: When salt-tolerant plants start to grow on the mudflats, they trap even more sediment. Over time, the mud builds up and creates a stable marshy landscape.

Memory Aid: "Slow water, Low energy, Mud settles."

4. Sea Level Change: Eustatic vs Isostatic

This is often the trickiest part of the chapter. To understand coastal landscapes, we need to know if the sea level is rising or the land is sinking.

Eustatic Change (Global)

This is a change in the actual volume of water in the oceans.
• When it’s cold (Ice Age), water is frozen on land as ice, so sea levels fall.
• When it’s warm (Global Warming), ice melts and water expands, so sea levels rise.
Mnemonic: Eustatic = Everywhere (Global).

Isostatic Change (Local)

This is when the land itself rises or falls. Think of the Earth's crust like a mattress. If you sit on it (add heavy ice), it sinks. If you stand up (ice melts), it slowly bounces back up. This "bounce" is called isostatic recovery.
Mnemonic: Isostatic = Ice (Land movement).

The Last 10,000 Years

Since the last Ice Age ended (about 10,000 years ago), we have seen a massive eustatic rise in sea levels as the great ice sheets melted. This has "drowned" many former land areas.

Quick Review:
• Eustatic: Sea level goes up or down.
• Isostatic: Land goes up or down.

5. Emergent and Submergent Coastlines

When sea levels change, they create entirely new types of landscapes.

Submergent Landscapes (Sea Level Rises)

These form when the sea "floods" the land:
• Rias: Drowned river valleys. They look like wide, branching estuaries. (Common in South West England).
• Fjords: Drowned glacial valleys. They have very steep sides and are very deep. (Common in Norway).
• Dalmatian Coasts: Where mountains run parallel to the coast, a rise in sea level creates a series of long, thin islands. (Named after the coast of Croatia).

Emergent Landscapes (Sea Level Falls / Land Rises)

These form when the land "pops out" of the sea:
• Raised Beaches: Former beaches that are now high above the current sea level. You might see old caves and stacks sitting in a field far from the water!
• Marine Platforms: Flat areas of former sea floor that have been pushed up above the waves.

Common Mistake to Avoid: Don't confuse a Ria with a Fjord! A Ria is a flooded river valley (V-shaped), while a Fjord is a flooded glacial valley (U-shaped and much deeper).

6. Climate Change and the Future

Recent and predicted climate change is causing sea levels to rise at an accelerating rate. Why?

1. Thermal Expansion: As the ocean warms, the water molecules move apart and take up more space.
2. Ice Melt: Glaciers and ice sheets (like Greenland) are melting, adding more water to the "bath."

Potential Impacts:
• Increased coastal flooding and erosion.
• Loss of habitats like saltmarshes.
• Huge economic costs for protecting coastal cities (like London or New York).

Key Takeaway: Coastal landscapes are not permanent. They are the result of processes working over thousands of years, but human-induced climate change is now speeding up these changes faster than ever before.