Author: masseys

Coasts

Erosion Processes
Erosion Features
Deposition Process—Longshore Drift
Deposition Feature
Named Examples and Map Work
Dorset Coast: Land Use, Conflicts & Solutions

Erosion Processes:
Abrasion: Where rocks carried by the waves are thrown at the cliffs and wear them away like sandpaper.
Hydraulic Action: Where water and air are forced into cracks in the cliff. The pressure breaks the rock apart.
Solution: Where the salty sea water reacts with chemicals in the rock face and dissolve areas.
Attrition: Happens to material carried in the water. Rocks bash off each other and become smaller and smoother.

Bays and Headlands:
No coastline is straight and it is never made up of the same rock the whole way along. The rocks that make up cliff faces can erode faster or slower depending on the strength of the rock.
Clay is a relatively soft rock and is eroded very quickly.
Chalk is a hard rock that takes longer to erode.
This is known as differential erosion and causes our coastlines to have areas of land that stick out into the sea and areas that come inwards.

Using the information about the processes of erosion and the rock types that make up coastlines you should write about how Bays and Headlands are formed.
Be sure to talk about:
Erosion Processes
The types of rock
Bays and Headlands

Wave-Cut Notches and Wave-Cut Platforms
Waves only reach up so far on a cliff. This means that the bottom of the cliff between high tide and low tide are eroded at a much faster rate.
This creates a notch at the bottom of a cliff called a wave-cut notch. This is created by Abrasion, solution and hydraulic action.

Over time this notch will get deeper and deeper into the cliff creating a large area of unsupported cliff above it.
This cliff will eventually become to heavy and collapse into the water below.
The rock will create a ledge of rock at the bottom of the cliff called a wave cut platform.

Faults, Caves, Arches, Stacks and Stumps
The areas of rock that stick out into the sea are called headlands. They allow for the water to erode the front and sides of the rock and they can create a series of features.
Water erodes a fault (crack) in the headland and makes it wider.
As the fault is made bigger it will create a cave.
The cave will be made wider and could eventually erode all the way through the area of rock to the other side. This creates a keyhole through the headland known as an arch.
The arch will continue to be eroded and when it gets too wide it will no longer be able to support its roof. This will collapse making the headland shorter with a stack of rock left standing in the sea.
This stack will be eroded further and will eventually collapse leaving a short stump of rock in the sea.

Longshore Drift
The material that is eroded from the cliffs is moved along the coastline by the sea. Its movement is determined by the prevailing wind which generally takes material from the SW Coasts to the SE Coasts.
As waves move in and out from beaches it carries rocks and sands in a very particular way. This is called Longshore drift.
Waves come into the beaches at a 45 degree angle on the Swash. It then goes back out to see in a straight line on the Backwash.

Write a description that tells me how material is moved along the coastlines.
Make sure to talk about:
SW prevailing wind
Angle the swash comes into the beach.
Angle the backwash leaves the beach.
The overall movement of material along the beach.

Spits, Bars, Lagoons and Tombolos
The material that is moved by Longshore drift will get dropped further along the coastline. This usually happens when waves take the material behind a headland. Here the water tends to be shallower and the waves less strong so the material is put down and builds up.
This creates beaches that come out from headlands and into the sea. These are known as Spits.
If a spit forms at the mouth of a bay it will often continue to grow across the entrance until it completely blocks the area off to the sea. This is known as a Bar.
The water that is trapped behind the bar is called a Lagoon and is refilled when there are particularly strong waves that break over the top.
If a spit grows out to sea it can join onto an island. This creates a beach from the mainland to the island and is known as a Tombolo.

Coastal Map work– Erosion Features
You should be able to identify features of Coastal Erosion including:
Headlands, Bays, Caves, Stacks and Cliffs.

Headland

Bay

Cliffs

Named Examples from Dorset
Stack = Old Harry
Arch = Durdle Door
Bay = Swanage Bay

Coastal Map work– Deposition Features
You should be able to identify features of Coastal deposition including:
Spits, Bars, Beaches, Lagoons and Tombolos

Lagoon

Bar

Beach

Named Examples from Dorset
Spit = Sandbanks
Tombolo = Chesil Beach
Lagoon = Fleet lagoon

Dorset Coast Case Study
We have to know a case study about how coastal landscapes are used by people. We will look at the Dorset Coast and investigate how the land can be used. The conflicts that land users can experience and some solutions to these conflicts.
Land Uses

Conflicts between land users in Poole Harbour
There are many conflicts in Poole harbour.
Conservationists who want to protect the wildlife clash with the oil drillers who could be polluting the waters.
Water sport users clash with fisherman as the noise and movement can scare away fish from the area.
The number of tourists visiting the area makes it difficult for the people living in Poole to travel around as the roads get congested.

Solutions to Poole Harbour Conflicts

Past Paper Questions
Use the following questions to help you revise this topic. All the answers will be within the booklet.

Erosion Processes

With the aid of annotated diagrams, explain the processes of erosion that create coastal features.
6 marks

With the aid of annotated diagrams, explain the formation of a stack.
Tips:
6 Marks

Erosion Features

Explain the formation of Bays and Headlands using an annotated diagram.
4 Marks

Deposition Features
With the aid of annotated diagrams, explain the formation of a spit. (6 marks)
Tips:
Land Use Conflicts

Ensure you include fully annotated diagrams
You will need to refer to caves and arches also
You will need to explain the erosion processes that are creating the features.

•You must include the processes that form the features e.g. for stack, hydraulic action, attrition, corrasion.

•What other landforms can be created by its expansion?

•What may form behind the sandspit?

What does a spit look like?
What conditions are needed for Coastal deposition to occur?
What happens if a spit joins across a bay, onto an island.
What process is taking place?

•Named example?