Coastal landscape development

Welcome to Coastal Landscape Development!

In this chapter, we are going to explore how the coast is like a giant, natural construction site. Some parts are being "demolished" (erosion), while others are being "built up" (deposition). We’ll also look at how changing sea levels have completely redesigned the map over thousands of years. Don’t worry if some of the terms sound a bit technical—we’ll break them down into simple pieces together!

1. Landforms of Coastal Erosion

Erosion happens when the sea attacks the land. Over time, this "attack" carves out spectacular shapes. Think of the sea as a sculptor using waves as its chisel.

Cliffs and Wave-Cut Platforms

When high waves hit the base of a cliff, they carve out a small "dent" called a wave-cut notch.
How it works: 1. The sea erodes the bottom of the cliff. 2. The rock above becomes unstable because nothing is holding it up. 3. Eventually, the top of the cliff collapses. 4. The cliff "retreats" (moves backward), leaving a flat, rocky floor at the base called a wave-cut platform.

Caves, Arches, Stacks, and Stumps

This is the "classic" sequence of coastal erosion. It usually happens on headlands (pieces of land sticking out into the sea).

Step-by-Step Process: 1. Cracks: The sea finds a weak spot (a crack) in the headland. 2. Cave: Erosion widens the crack into a cave. 3. Arch: The cave is eroded all the way through the headland, creating an arch. 4. Stack: The roof of the arch becomes too heavy and collapses, leaving an isolated pillar of rock called a stack. 5. Stump: The sea attacks the base of the stack until it falls, leaving a small stump that might only be visible at low tide.

Quick Memory Aid: Use the mnemonic C-A-S-S (Cave, Arch, Stack, Stump) to remember the order!

Quick Review: Erosion landforms are created by the sea taking material away. The main features are cliffs, platforms, caves, arches, stacks, and stumps.

2. Landforms of Coastal Deposition

Deposition happens when the sea "runs out of breath" (loses energy) and drops the sand or pebbles it was carrying. This creates new land.

Beaches

Beaches are the most common depositional landform. They form in sheltered areas like bays. Constructive waves (gentle waves) build them up by pushing sand onto the shore with a strong swash.

Spits, Tombolos, and Bars

These features are all formed by Longshore Drift (the zig-zag movement of sediment 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 (like at a river mouth).
Analogy: Think of a spit like a long finger pointing out from the land.

Tombolos: A spit that grows so long it connects the mainland to an island.
Example: Chesil Beach in the UK connects the Isle of Portland to the mainland.

Bars: A spit that grows all the way across a bay, joining two headlands and trapping a "lake" of water behind it called a lagoon.

Sand Dunes

Sand dunes are hills of sand built by the wind. They need a wide beach and plants (like Marram Grass) to "trap" the sand.
Did you know? The first plants to grow on a dune are called pioneer species. They are tough enough to survive the salty, dry conditions!

Key Takeaway: Deposition landforms are "additions" to the coast. They rely on a steady supply of sediment and low-energy waves.

3. Estuarine Environments

Where rivers meet the sea (estuaries), the water slows down even more. This allows very fine silt and mud to settle.

Mudflats: Flat areas of mud exposed at low tide.
Saltmarshes: Over time, plants start to grow on the mudflats. These plants trap more sediment, and the land slowly rises above the sea level. This is a very important habitat for birds and fish!

4. Sea Level Change

The sea level isn't fixed; it goes up and down over thousands of years. This happens for two main reasons:

Eustatic vs. Isostatic (The "E" and "I" trick)

Eustatic Change: Global change. The actual volume of water in the ocean changes (e.g., when ice melts).
Memory Trick: Eustatic is Everywhere (Global).

Isostatic Change: Local change. The land itself rises or sinks. This happens because the heavy weight of ice during the last Ice Age pushed the land down. Now the ice is gone, the land is slowly "springing" back up.
Memory Trick: Isostatic is Individual (Local land).

5. Coastlines of Emergence and Submergence

When sea levels change, they create very specific landscapes.

Submergent Coastlines (Sea level rises or land sinks)

Rias: Drowned river valleys. They look like wide, winding inlets.
Fjords: Drowned glacial valleys. They have very steep, high sides and are very deep.
Dalmatian Coasts: Form where valleys run parallel to the coast. When the sea rises, it floods the valleys, leaving the tops of the hills sticking out as a chain of long islands.

Emergent Coastlines (Sea level falls or land rises)

Raised Beaches: Former beaches that are now high above the current sea level. You might see old sea caves or stacks standing in the middle of a field!
Marine Platforms: An old wave-cut platform that has been lifted out of the sea.

Common Mistake: Students often confuse Rias and Fjords. Remember: Rias are made by Rivers (winding); Fjords are made by Glaciers (U-shaped and very steep).

6. Recent Climate Change and the Future

Global warming is causing Eustatic sea level rise because polar ice is melting and the ocean water is expanding as it gets warmer (thermal expansion).

The Impact: 1. Increased Flooding: Low-lying areas (like Bangladesh or the Maldives) are at risk. 2. Faster Erosion: Higher sea levels mean waves can reach higher up the cliffs, attacking them more often. 3. Loss of Habitats: Saltmarshes can be trapped between the rising sea and human sea walls. This is called "coastal squeeze."

Encouragement: This is a lot of information, but remember that it's all about one simple thing: the balance between the power of the sea and the resistance of the land!

Quick Review Box

Processes: Erosion (wearing away) vs. Deposition (building up).
Erosion Features: Cliffs, Platforms, Caves, Arches, Stacks.
Deposition Features: Beaches, Spits, Tombolos, Bars, Dunes.
Sea Level: Eustatic (Global/Water) and Isostatic (Local/Land).
Submergent: Rias, Fjords, Dalmatian coasts.
Emergent: Raised beaches.