higher coasts lithosphere

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Higher Coasts Lithosphere

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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. - PowerPoint PPT Presentation

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Page 1: Higher Coasts Lithosphere

Higher Coasts Lithosphere

Page 2: Higher Coasts Lithosphere

Higher Coastal Landforms & Processes

In this part of the course we will be looking at both:coastal erosion and deposition.

Page 3: Higher Coasts Lithosphere

Coastal Erosion

We will be looking at the following:

1)Waves our agent of erosion2) Different types of erosion3) Landforms of erosion

Page 4: Higher Coasts Lithosphere

Coastal Deposition

We will be looking at: a. Beach profiles (X sections) & WaveTypes b. Longshore Drift c. Landforms of deposition

Page 5: Higher Coasts Lithosphere

Coastal ErosionTo 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.

Page 6: Higher Coasts Lithosphere

Fetch = Distance + Wind

Fetch = Distance + Wind

Page 7: Higher Coasts Lithosphere

Coastal Erosion

Now for Task 2 all about waves actually

breaking down rock, or erosion.

Page 8: Higher Coasts Lithosphere

Crashing Waves Erode Land

Page 9: Higher Coasts Lithosphere

Wave Erosion

There are 3 ways that waves 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.

Page 10: Higher Coasts Lithosphere

The Three Main Types Of Erosion

Page 11: Higher Coasts Lithosphere

Hydraulic Pressure

Breaking Wave

Crack In

Rock

Air Compressed

By Water

Page 12: Higher Coasts Lithosphere

Hydraulic Pressure

Air explodes

out of crack

Over time rock

weakens and breaks

off cliff

Page 13: Higher Coasts Lithosphere

Hydraulic PressureKey words to describe hydraulic pressure.breaking waves ~ cliff ~ water ~

cracks compresses air ~ air explodes ~ rock ~ time ~ breaks ~ force of water pounding ~ erodes ~ time

Page 14: Higher Coasts Lithosphere

CorrasionWaves carry rocks,

shingle, sand

Rocks hit each

other

Rocks erode over

time

Page 15: Higher Coasts Lithosphere

Corrasion (abrasive)Key words to describe corrasion.

broken rock ~ picked ~ waves thrown ~ cliff faces ~ hard rock -

erode ~ time

Page 16: Higher Coasts Lithosphere

Attrition

Small rocks rub

against cliff

Waves carry rocks

Page 17: Higher Coasts Lithosphere

AttritionKey words to describe attrition.

small rocks ~ H.P. ~ Corrasion waves ~ rub ~ cliff ~ erosion

Page 18: Higher Coasts Lithosphere

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.

Page 19: Higher Coasts Lithosphere

Landforms Of Coastal Erosion

We shall look at three principal types of landforms:i.  Cliffs/Wave Cut Platformsii. Headlands/Baysiii.Headland Erosion (On Sides)

Page 20: Higher Coasts Lithosphere

sea cliff erosion

wave cut

platform

Sea Cliff ErosionWave Cut Platforms

(Task 3)

Page 21: Higher Coasts Lithosphere

Sea Cliff ErosionCracks In rock are

weak points

These are eroded by waves at

high tides by the 4

processes we’ve looked

Page 22: Higher Coasts Lithosphere

Sea Cliff Erosion

cracks get larger & form a cave

undercutting of cliff by

cave

collapse of

overhang

Page 23: Higher Coasts Lithosphere

Sea Cliff Erosion

Repeated collapse

over time

flat terrace remnant of base of cliff

Page 24: Higher Coasts Lithosphere

Sea Cliff Erosion

Now do Task 3 Question 1 by filling in the key

Page 25: Higher Coasts Lithosphere

Wave Cut Platform

for later

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

created at high tide

Page 26: Higher Coasts Lithosphere

Task 3 Question 21)Waves ~ erosion ~ 4 types ~

name ~ general effect ~ high tide2) Cracks ~ weak ~ widen ~ wave cut notch ~ cave ~ time ~ overhang ~ collapse of cliff (why) ~ repeats ~ retreats

3)Base of cliff ~ flat terrace ~ name it ~ exposed low tide

Page 27: Higher Coasts Lithosphere

Headlands & Bays Task 4large headland

small headland

large bay

small bay

Page 28: Higher Coasts Lithosphere

Headlands & Bays

two types

concordant parallel

to sea

discordant at 90º to

sea

Page 29: Higher Coasts Lithosphere

Concordant Headlandscrack in rock

eroded by wavessoft rock

hard rock

hard rock resists waves so narrow crack

Page 30: Higher Coasts Lithosphere

Concordant Headlands

Bay

Headland

soft rock erodes easily so wide bay

Page 31: Higher Coasts Lithosphere

Discordant Headlandssoft rock hard rock

softer rocks erode more easily than harder ones ~ differential erosion

Page 32: Higher Coasts Lithosphere

Discordant Headlands

bay

headland

indents or bays form on the coast where the soft rock has receded

Page 33: Higher Coasts Lithosphere

Task Question 3

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

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

Page 34: Higher Coasts Lithosphere

Headland Erosion (On Sides)

These are a series of landforms

developing one after the other on

the side of a headland.

Page 35: Higher Coasts Lithosphere

Caves/Blowholes/Arches/StacksLabel the sketch below in your work book using the word box for task 7.

Page 36: Higher Coasts Lithosphere

Caves/Blowholes/Arches/Stacks

cavewave cut platform

blowhole

arch

stack needle

Page 37: Higher Coasts Lithosphere

Caves/Blowholes/Arches/Stacks 1erosion

on side of headland

waves erode cracks into

caves

Page 38: Higher Coasts Lithosphere

Caves/Blowholes/Arches/Stacks 1 Cont.

name your 3 types of erosion in exam

Explain sedimentar

y rocks easily

exploited many cracks

Page 39: Higher Coasts Lithosphere

Caves/Blowholes/Arches/Stacks 2blowhole in

top of headland

waves crash into back of cave and erode upwards into headland

Page 40: Higher Coasts Lithosphere

Caves/Blowholes/Arches/Stacks 2 Cont.

blowholes are relatively rare

vertical cracks in rock help them to

form

Page 41: Higher Coasts Lithosphere

Blowhole

Roof collapses due to erosion

from waves splashing

upwards from back of cave

Page 42: Higher Coasts Lithosphere

Caves/Blowholes/Arches/Stacks 3

continued erosion of back of cave

eventual break through to other side

forms an arch

Page 43: Higher Coasts Lithosphere

Caves/Blowholes/Arches/Stacks 3 Cont.

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

Page 44: Higher Coasts Lithosphere

Caves/Blowholes/Arches/Stacks 4

further erosion sees widening of arch

little support so eventual collapse

of roof

Page 45: Higher Coasts Lithosphere

Caves/Blowholes/Arches/Stacks 4 Cont.

process can be aided by blowhole weakening roof

Page 46: Higher Coasts Lithosphere

Caves/Blowholes/Arches/Stacks

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

Page 47: Higher Coasts Lithosphere

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.

Page 48: Higher Coasts Lithosphere

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!).

Page 49: Higher Coasts Lithosphere

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 the cave 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!

Page 50: Higher Coasts Lithosphere

Caves/Blowholes/Arches/Stacks8) 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.

Page 51: Higher Coasts Lithosphere

Coastal DepositionThis is essentially all about

beaches and why they develop. We will look at:

1)Swash & Backwash2)Beach Profiles3)Beach Angle & Wave Type4)Longshore Drift5)Landfroms Of Deposition

Page 52: Higher Coasts Lithosphere

Why Beaches DevelopBeaches develop where

material is deposited due to:

1)Sheltered areas reducing wave velocity

2)A large supply of sediment from eroded features

3)Longshore Drift maintaining a beach

Page 53: Higher Coasts Lithosphere

Swash & Backwash

swash

backwash

Page 54: Higher Coasts Lithosphere

Swash & Backwash

water swashing

up a beach

Page 55: Higher Coasts Lithosphere

Why Beaches Develop Swash & Backwash Task 8

Backwash

Swash

Page 56: Higher Coasts Lithosphere

Gentle Beach Constructive Waves

circular ellipticalstrong swash

weak backwash

Page 57: Higher Coasts Lithosphere

Gentle Beach Constructive Waves

Now for Task 9 Question 1

Complete the passage using the word box

Page 58: Higher Coasts Lithosphere

Steep Beach Destructive Waves

strong backwash

weak swash

circular wave

elliptical wave

rotation of wave

Page 59: Higher Coasts Lithosphere

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

Page 60: Higher Coasts Lithosphere

Longshore Drift

breaking swash breaks at angle on beach

Page 61: Higher Coasts Lithosphere

Longshore Drift

Swash loses energy & backwash returns straight down beach due to

gravity

Page 62: Higher Coasts Lithosphere

Longshore Drift

Zigzag movement of sediment with swash & backwash means

sediment moved along beach

Page 63: Higher Coasts Lithosphere

Longshore Driftswash backwas

h

direction of longshore drift moving

sediment

Page 64: Higher Coasts Lithosphere

Longshore DriftExplaining longshore drift Task 10

swash angle ~ energy loss ~ backwash ~ gravity ~ straight down ~ carries sediment ~ up ~ down ~ along beach

Page 65: Higher Coasts Lithosphere

Landforms Of Coastal Deposition

We will look at three main landforms other than

standard beaches:

1)Spits2)Bars3)Tombolos

Page 66: Higher Coasts Lithosphere

Spit Photograph

Spit

Longshore Drift

Page 67: Higher Coasts Lithosphere

Spit bay

longshore drift

Page 68: Higher Coasts Lithosphere

Spitspit

bay

longshore drift

Page 69: Higher Coasts Lithosphere

Spit help

Page 70: Higher Coasts Lithosphere

Bar Photograph

BarLagoon

Longshore Drift

Page 71: Higher Coasts Lithosphere

Bars Bay

longshore drift

Page 72: Higher Coasts Lithosphere

Bars lagoon

longshore drift

bar

Page 73: Higher Coasts Lithosphere

Bar help

Page 74: Higher Coasts Lithosphere

Tombolo PhotographIsland

Tombolo

Longshore Drift

Page 75: Higher Coasts Lithosphere

Tombolo

island

bay

longshore drift

Page 76: Higher Coasts Lithosphere

Tombolo

island

bay

tombolo

spit

Page 77: Higher Coasts Lithosphere

Tombolo help

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