Welcome to the Dynamic World of Coastal Landscapes!
Hello there! Welcome to your study guide for Coastal Landscapes. This chapter is part of your Landscape Systems section. We are going to explore how the coast isn't just a place for holidays, but a giant, moving machine (or "system") that is constantly being shaped by nature and humans. Don't worry if some of the terms seem a bit "rocky" at first—we'll break them down step-by-step!
1. Coastal Landscapes as Systems
Think of a coastal landscape like a giant factory. To keep the factory running, you need stuff coming in (raw materials), things happening inside (processes), and stuff coming out (finished products).
The System Components
In Geography, we call these:
• Inputs: These are things entering the system, like energy from waves, wind, and tides, or material like sediment (sand and pebbles).
• Processes: These are the "actions" happening at the coast, like erosion (wearing away rock) or transportation (moving sand along the beach).
• Outputs: These are the results, like depositional landforms (e.g., a new sand spit) or sediment being carried out to the deep ocean.
Sediment Cells
A Sediment Cell is like a "closed loop" section of the coast. Within one cell, sediment moves around, but very little of it escapes to the next cell. It’s like a self-contained recycling center for sand!
Quick Review: If the inputs and outputs of sediment are equal, the beach is in equilibrium (it stays the same size).
The Sediment Budget Formula:
To calculate if a beach is growing or shrinking, we look at the balance:
\( \text{Sediment Budget} = \text{Total Inputs} - \text{Total Outputs} \)
Key Takeaway: Coasts are open systems because they exchange energy and matter with their surroundings. If you change one part (like building a wall), the rest of the system will react!
2. Factors Influencing the Coast
Why do some coasts have massive cliffs while others have flat, sandy beaches? It’s all down to these physical factors:
Winds and Waves
Wind is the engine. It creates waves. The stronger the wind, the longer it blows, and the further it travels over the water (the fetch), the bigger and more powerful the waves will be.
• Constructive Waves: These are "calm" waves that build beaches up. They have a strong swash (water moving up the beach) and a weak backwash (water pulling back).
• Destructive Waves: These are "angry" waves that strip beaches away. They have a weak swash and a very strong backwash.
Geology (The "Ingredients")
This is about the rocks themselves. Geographers look at two things:
1. Lithology: The type of rock. Hard rocks (like granite) erode slowly. Soft rocks (like clay) erode quickly.
2. Structure: How the rock is put together. Are there cracks (joints) or layers (faults)? If the layers run parallel to the sea, it's a concordant coast. If they run at right angles, it's a discordant coast (this is where you get headlands and bays!).
Memory Aid: "Lithology is the Ingredient, Structure is the Recipe."
Key Takeaway: The "strength" of the waves versus the "resistance" of the rocks determines how the coast looks.
3. Where Does the Sediment Come From?
Sediment doesn't just appear by magic! It comes from several sources:
• Terrestrial (Land): Rivers bring silt and mud (fluvial), or cliffs crumble down due to weathering and mass movement (like landslides).
• Offshore: Waves can push sand from the seabed onto the shore.
• Human: We sometimes add sand to beaches to protect them—this is called beach nourishment.
4. Geomorphic Processes: Shaping the Land
These are the tools nature uses to sculpt the coast. Don't worry if these seem tricky; just think of them as "nature's sandpaper."
Erosion (Wearing it down)
• Hydraulic Action: Waves trap air in cliff cracks. The pressure becomes so high it literally "pops" the rock apart.
• Abrasion: Waves hurl pebbles against the cliff. Think of this as sandpapering the coast.
• Attrition: Rocks in the sea smash into each other and become smaller, rounder, and smoother.
Transportation and Deposition
Longshore Drift (LSD): This is the most important process for moving material!
1. Waves approach the beach at an angle (pushed 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 creates a "zigzag" movement along the shore.
Did you know? Without Longshore Drift, many of our famous seaside towns wouldn't have beaches at all!
5. Coastal Landforms
Landforms are the "features" created by the processes above. We divide them into two groups:
Erosional Landforms (The "High Energy" coast)
Usually found where waves are powerful.
• The "Cave-Arch-Stack-Stump" sequence: A crack in a headland widens into a cave. The cave erodes all the way through to become an arch. The roof of the arch collapses, leaving a pillar of rock called a stack. Eventually, the stack falls, leaving a stump.
Depositional Landforms (The "Low Energy" coast)
Found where waves lose energy and "drop" their load.
• Spits: Long ridges of sand attached to the land at one end, stretching out across an estuary.
• Tombolos: A spit that grows so long it connects the mainland to an island! (Example: Chesil Beach in the UK).
• Salt Marshes: Sheltered areas behind spits where mud builds up and plants start to grow.
Key Takeaway: Erosional landforms show nature's power to destroy; depositional landforms show nature's power to build.
6. Changing Sea Levels (Climate Change)
As the climate changes, sea levels rise or fall, creating new types of landscapes.
Emergent Landscapes (Sea level FALLS)
When the climate cools, water is trapped as ice, and the sea level drops.
• Raised Beaches: Former beaches that are now high above the current sea level.
• Abandoned Cliffs: Old cliffs that are no longer reached by the sea.
Submergent Landscapes (Sea level RISES)
When the climate warms, ice melts and the sea level rises, "drowning" the land.
• Rias: Drowned river valleys (they look like wide, winding estuaries).
• Fjords: Drowned glacial valleys (very deep with steep, U-shaped sides).
• Shingle Beaches: As sea levels rise, they push "shingle" (pebbles) onshore.
7. Human Activity: Friend or Foe?
Humans love the coast, but our presence changes the "system."
Intentional Change (Management)
We build things on purpose to protect the coast.
• Groynes: Wooden fences built into the sea to stop Longshore Drift. They catch sand and make the beach wider.
• Impact: While groynes protect one beach, they starve the beach "down-drift" of sand, causing more erosion elsewhere! This is a classic interference in the sediment budget.
Unintentional Change (Economic Development)
Sometimes we change the coast by accident.
• Offshore Dredging: Taking sand from the seabed for construction. This can make the water deeper, allowing bigger, more destructive waves to reach the shore.
• Tourism/Ports: Building large ports can block the natural flow of sediment, leading to unexpected beach loss or "retreat" in nearby areas.
Quick Review: Humans often try to fix a problem at the coast, but because it is a system, our "fix" usually creates a new problem somewhere else!
Summary Checklist for Success
To ace this chapter, make sure you can:
1. Explain the coast as a system (Inputs -> Processes -> Outputs).
2. Describe how waves, geology, and wind influence the shape of the land.
3. Explain the zigzag movement of Longshore Drift.
4. Identify Erosional (e.g., Stacks) and Depositional (e.g., Spits) landforms.
5. Contrast Emergent (Raised beaches) and Submergent (Rias/Fjords) landscapes.
6. Discuss how human management (like groynes) affects the sediment budget.
Don't forget to look at your specific case studies (one high-energy, one low-energy, and one managed coast) to see these processes in the real world!