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Higher Coasts Lithosphere. Higher Coastal Landforms & Processes. In this part of the course we will be looking at both: coastal erosion and deposition. Coastal Erosion. We will be looking at the following: Waves our agent of erosion Different types of erosion Landforms of erosion.

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Higher coastal landforms processes
Higher Coastal Landforms & Processes

In this part of the course we will be looking at both:

coastal erosion

and

deposition.


Coastal erosion
Coastal Erosion

  • We will be looking at the following:

  • Waves our agent of erosion

  • Different types of erosion

  • Landforms of erosion


Coastal deposition
Coastal Deposition

  • We will be looking at:

  • a. Beach profiles (X sections) & WaveTypes

  • b. Longshore Drift

  • c. Landforms of deposition


Coastal erosion1
Coastal Erosion

To start, we must recognise that waves are responsible for coastal erosion and that generally the bigger the wave, and the more frequent, the greater the erosion.This means that we will need to look at how waves form and differ in size. To do this we will look at Task 1 in your work book.


Fetch distance wind
Fetch = Distance + Wind

Fetch = Distance + Wind


Coastal erosion2
Coastal Erosion

Now for Task 2 all about waves actually breaking down rock, or erosion.



Wave erosion
Wave Erosion

There are 3 ways thatwaves erode the coast. It is very important to describe and explain these as that will get you easy marks in an exam. You’ll need to show how they contribute towards the development of coastally eroded landforms. Watch the slides to find out more.


The three main types of erosion
The Three Main Types Of Erosion


Hydraulic pressure
Hydraulic Pressure

Crack In Rock

Breaking Wave

Air Compressed By Water


Hydraulic pressure1
Hydraulic Pressure

Over time rock weakens and breaks off cliff

Air explodes out of crack


Hydraulic pressure2
Hydraulic Pressure

Key words to describe hydraulic pressure.

breaking waves ~ cliff ~ water ~ cracks

compresses air ~ air explodes ~

rock ~ time ~ breaks ~ force of water pounding ~ erodes ~ time


Corrasion
Corrasion

Waves carry rocks, shingle, sand

Rocks hit each other

Rocks erode over time


Corrasion abrasive
Corrasion (abrasive)

Key words to describe corrasion.

broken rock ~ picked ~ waves

thrown ~ cliff faces ~ hard rock -erode ~ time


Attrition
Attrition

Waves carry rocks

Small rocks rub against cliff


Attrition1
Attrition

Key words to describe attrition.

small rocks ~ H.P. ~ Corrasion

waves ~ rub ~ cliff ~ erosion


Corrosion a fourth type of erosion
Corrosion A Fourth Type Of Erosion

This is when the rock is broken down by chemicals in the sea such as salt. Rocks can either dissolve or rot and so start to crumble away. This is similar to solution in Limestone areas or the corrosion of stone carried in rivers.


Landforms of coastal erosion
Landforms Of Coastal Erosion

We shall look at three principal types of landforms:

i.  Cliffs/Wave Cut Platforms

ii. Headlands/Bays

iii.Headland Erosion (On Sides)


Sea Cliff Erosion

Wave Cut Platforms

(Task 3)

wave cut platform

sea cliff erosion


Sea cliff erosion
Sea Cliff Erosion

Cracks In rock are weak points

These are eroded by waves at high tides by the 4 processes we’ve looked


Sea cliff erosion1
Sea Cliff Erosion

collapse of overhang

cracks get larger & form a cave

undercutting of cliff by cave


Sea cliff erosion2
Sea Cliff Erosion

Repeated collapse over time

flat terrace remnant of base of cliff


Sea cliff erosion3
Sea Cliff Erosion

Now do Task 3 Question 1 by filling in the key


Wave cut platform
Wave Cut Platform

W.C.P. exposed at low tide, but created at high tide

for later


Task 3 question 2
Task 3 Question 2

  • Waves ~ erosion ~ 4 types ~ name ~ general effect ~ high tide

  • Cracks ~ weak ~ widen ~ wave cut notch ~ cave ~ time ~ overhang ~ collapse of cliff (why) ~ repeats ~ retreats

  • Base of cliff ~ flat terrace ~ name it ~ exposed low tide


Headlands bays task 4
Headlands & Bays Task 4

large headland

large bay

small bay

small headland


Headlands bays
Headlands & Bays

concordant parallel to sea

two types

discordant at 90º to sea


Concordant headlands
Concordant Headlands

crack in rock eroded by waves

soft rock

hard rock

hard rock resists waves so narrow crack


Concordant headlands1
Concordant Headlands

Bay

Headland

soft rock erodes easily so wide bay


Discordant headlands
Discordant Headlands

soft rock

hard rock

softer rocks erode more easily than harder ones ~ differential erosion


Discordant headlands1
Discordant Headlands

bay

headland

indents or bays form on the coast

where the soft rock has receded


Task question 3
Task Question 3

  • Geology ~ 2 key factors ~ (1) different rock types ~ hard ~ soft ~ side by side ~ (2) Layers 90º ~ sea

  • Waves erode ~ hard rock ~ slow ~ resistant ~ soft rock ~ fast ~ soft indents ~ bays hard rock ~ sticks out ~ headlands


Headland erosion on sides
Headland Erosion (On Sides)

These are a series of landforms developing one after the other on the side of a headland.


Caves blowholes arches stacks
Caves/Blowholes/Arches/Stacks

Label the sketch below in your work book using the word box for task 7.


Caves blowholes arches stacks1
Caves/Blowholes/Arches/Stacks

stack

blowhole

needle

wave cut platform

cave

arch


Caves blowholes arches stacks 1
Caves/Blowholes/Arches/Stacks 1

erosion on side of headland

waves erode cracks into caves


Caves blowholes arches stacks 1 cont
Caves/Blowholes/Arches/Stacks 1 Cont.

Explain sedimentary rocks easily exploited many cracks

name your 3 types of erosion in exam


Caves blowholes arches stacks 2
Caves/Blowholes/Arches/Stacks 2

blowhole in top of headland

waves crash into back of cave and erode upwards into headland


Caves blowholes arches stacks 2 cont
Caves/Blowholes/Arches/Stacks 2 Cont.

blowholes are relatively rare

vertical cracks in rock help them to form


Blowhole
Blowhole

Roof collapses due to erosion from waves splashing upwards from back of cave


Caves blowholes arches stacks 3
Caves/Blowholes/Arches/Stacks 3

eventual break through to other side forms an arch

continued erosion of back of cave


Caves blowholes arches stacks 3 cont
Caves/Blowholes/Arches/Stacks 3 Cont.

process can be sped up if cracks on other side being eroded


Caves blowholes arches stacks 4
Caves/Blowholes/Arches/Stacks 4

little support so eventual collapse ofroof

further erosion sees widening of arch


Caves blowholes arches stacks 4 cont
Caves/Blowholes/Arches/Stacks 4 Cont.

process can be aided by blowhole weakening roof


Caves blowholes arches stacks2
Caves/Blowholes/Arches/Stacks

Now try and piece together the explanations for all of these landforms Task 7 question 2


Caves blowholes arches stacks3
Caves/Blowholes/Arches/Stacks

1)Waves crash into headlands eroding weaker parts such as cracks.

2)The cracks are eroded by 3 different processes:- hydraulic

pressure, corrasion & attrition. In an exam you should explain each of these!

3)The crack starts to widen and form a cave, it can be

undercut causing the roof to collapse due to lack of support

for the roof. This helps the cave get larger.


Caves blowholes arches stacks4
Caves/Blowholes/Arches/Stacks

4) As the cave gets larger, waves start to hit into its

back wall and on impact are sent crashing into the roof

of the cave where erosion occurs.

5)The erosion of the cave roof can lead to a blowhole,

where waves continue to erode upwards and through the

top of the headland. This is quite rare and needs a vertical crack line to be exploited (Sedimentary Rocks!).


Caves blowholes arches stacks5
Caves/Blowholes/Arches/Stacks

6) At the same time caves and blowholes develop, wave

erosion can also lead to the development of an arch. This is when thecave erodes all the way through to the other side of the headland.

7) There may be similar cracks on the other side of the

headland with erosion taking place, speeding up the

development of the arch. Arches don’t necessary need blow

holes to be present when they develop!


Caves blowholes arches stacks6
Caves/Blowholes/Arches/Stacks

8) Over time the waves continue to widen the walls of the

arch leaving less support for the roof, leading to its collapse.

This leaves a new headland on the landward side of the arch and the old wall still standing on the seaward side.

9) this old wall is called a stack or a pillar and is also subject

to erosion by the sea. As it erodes it gets thinner at its base

and parts of it collapse leaving a narrower pillar called a

needle.


Coastal deposition1
Coastal Deposition

  • This is essentially all about beaches and why they develop. We will look at:

  • Swash & Backwash

  • Beach Profiles

  • Beach Angle & Wave Type

  • Longshore Drift

  • Landfroms Of Deposition


Why beaches develop
Why Beaches Develop

  • Beaches develop where material is deposited due to:

  • Sheltered areas reducing wave velocity

  • A large supply of sediment from eroded features

  • Longshore Drift maintaining a beach


Swash backwash
Swash & Backwash

swash

backwash


Swash backwash1
Swash & Backwash

water swashing up a beach



Gentle beach constructive waves
Gentle Beach Constructive Waves

strong swash

circular

elliptical

weak backwash


Gentle beach constructive waves1
Gentle Beach Constructive Waves

Now for Task 9 Question 1

Complete the passage

using the word box


Steep beach destructive waves
Steep Beach Destructive Waves

elliptical wave

circular wave

weak swash

rotation of wave

strong backwash


Steep beach destructive waves1
Steep Beach Destructive Waves

Now for Task 9 Question 2

wave ~ friction ~ seabed ~ elliptical ~

just before breaking ~ steep wave ~

rotates back ~ weak swash ~ strong

backwash ~ sediment lost ~

destructive wave


Longshore drift
Longshore Drift

breaking swash breaks at angle on beach


Longshore drift1
Longshore Drift

Swash loses energy & backwash returns straight down beach due to gravity


Longshore drift2
Longshore Drift

Zigzag movement of sediment with swash & backwash means sediment moved along beach


Longshore drift3
Longshore Drift

swash

backwash

direction of longshore drift

moving sediment


Longshore drift4
Longshore Drift

Explaining longshore drift Task 10

swash angle ~ energy loss ~ backwash ~

gravity ~ straight down ~ carries

sediment ~ up ~ down ~ along beach


Landforms of coastal deposition
Landforms Of Coastal Deposition

We will look at three main landforms other than standard beaches:

  • Spits

  • Bars

  • Tombolos


Spit photograph

Longshore Drift

Spit Photograph

Spit


bay

Spit

longshore drift


Spit

bay

spit

longshore drift



Bar photograph
Bar Photograph

Longshore Drift

Lagoon

Bar


Bay

Bars

longshore drift


lagoon

Bars

bar

longshore drift



Tombolo photograph
Tombolo Photograph

Island

Longshore Drift

Tombolo


Tombolo
Tombolo

bay

island

longshore drift


Tombolo1
Tombolo

bay

spit

island

tombolo



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