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:
1)Waves our agent of erosion
2) Different types of erosion
3) Landforms of erosion
Coastal Deposition
We will be looking at:
a. Beach profiles (X sections) & WaveTypes
b. Longshore Drift
c. Landforms of deposition
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
Coastal Erosion
Now for Task 2 all about
waves actually breaking
down rock, or erosion.
Crashing Waves Erode Land
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.
The Three Main
Types Of Erosion
Hydraulic Pressure
Breaking
Wave
Crack
In
Rock
Air
Compressed
By Water
Hydraulic Pressure
Over time
rock weakens
and breaks
off cliff
Air
explodes
out of crack
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
Waves
carry
rocks,
shingle,
sand
Rocks
hit each
other
Rocks erode
over time
Corrasion (abrasive)
Key words to describe corrasion.
broken rock ~ picked ~ waves
thrown ~ cliff faces ~ hard rock erode ~ time
Attrition
Waves
carry
rocks
Small
rocks rub
against
cliff
Attrition
Key words to describe attrition.
small rocks ~ H.P. ~ Corrasion
waves ~ rub ~ cliff ~ 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
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
wave cut
platform
sea cliff
erosion
(Task 3)
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 Erosion
collapse of
overhang
undercutting
of cliff by cave
cracks get
larger &
form a cave
Sea Cliff Erosion
Repeated
collapse
over time
flat terrace remnant of base of cliff
Sea Cliff Erosion
Now do Task 3 Question 1
by filling in the key
Wave Cut Platform
W.C.P. exposed at
low tide, but created
at high tide
for later
Task 3 Question 2
1) Waves ~ erosion ~ 4 types ~ name ~
general effect ~ high tide
2) 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
Headlands & Bays Task 4
large
bay
large headland
small
headland
small
bay
Headlands & Bays
concordant
parallel to
sea
two types
discordant
at 90º to
sea
Concordant Headlands
soft
rock
crack in rock
eroded by waves
hard
rock
hard rock resists waves so narrow crack
Concordant Headlands
Bay
Headland
soft rock erodes easily so wide bay
Discordant Headlands
soft rock
hard rock
softer rocks erode more easily than
harder ones ~ differential erosion
Discordant Headlands
bay
headland
indents or bays form on the coast
where the soft rock has receded
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
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
Label the sketch below in your work book
using the word box for task 7.
Caves/Blowholes/Arches/Stacks
blowhole
wave cut platform
stack
cave
needle
arch
Caves/Blowholes/Arches/Stacks 1
erosion on
side of
headland
waves erode
cracks into caves
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
blowhole in
top of
headland
waves crash into back of cave and
erode upwards into headland
Caves/Blowholes/Arches/Stacks 2 Cont.
blowholes are
relatively rare
vertical cracks in rock
help them to form
Blowhole
Roof collapses
due to erosion
from waves
splashing
upwards from
back of cave
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.
process can be sped up if cracks
on other side being eroded
Caves/Blowholes/Arches/Stacks 4
little support so
eventual collapse
of roof
further erosion sees
widening of arch
Caves/Blowholes/Arches/Stacks 4 Cont.
process can be aided by
blowhole weakening roof
Caves/Blowholes/Arches/Stacks
Now try and piece
together the explanations
for all of these landforms
Task 7 question 2
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/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/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!
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 Deposition
This is essentially all about
beaches and why they
develop. We will look at:
1) Swash & Backwash
2) Beach Profiles
3) Beach Angle & Wave Type
4) Longshore Drift
5) Landfroms Of Deposition
Why Beaches Develop
Beaches 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
Swash & Backwash
swash
backwash
Swash & Backwash
water
swashing up
a beach
Why Beaches Develop
Swash & Backwash Task 8
Swash
Backwash
Gentle Beach Constructive Waves
circular
elliptical
weak backwash
strong
swash
Gentle Beach Constructive Waves
Now for Task 9 Question 1
Complete the passage
using the word box
Steep Beach Destructive Waves
circular wave
elliptical wave
weak
swash
rotation
of wave
strong
backwash
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
breaking swash breaks
at angle on beach
Longshore Drift
Swash loses energy & backwash
returns straight down beach due to
gravity
Longshore Drift
Zigzag movement of sediment
with swash & backwash means
sediment moved along beach
Longshore Drift
swash
direction of
longshore drift
backwash
moving sediment
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
We will look at three main
landforms other than
standard beaches:
1) Spits
2) Bars
3) Tombolos
Spit Photograph
Spit
Longshore
Drift
Spit
longshore drift
bay
Spit
spit
longshore drift
bay
Spit help
Bar Photograph
Longshore
Drift
Lagoon
Bar
Bars
longshore drift
Bay
Bars
bar
longshore drift
lagoon
Bar help
Tombolo Photograph
Island
Longshore
Drift
Tombolo
Tombolo
bay
island
longshore drift
Tombolo
spit
bay
island
tombolo
Tombolo help