Transcript HIGHER GEOGRAPHY

LITHOSPHERE CORE
COASTLINES
Title: Coastal Landscapes
Date: 20/07/2015
Aims:
To learn about the different ways in which the landscape at coasts can
change.
To learn about the different features found at coasts (more than NAT 5)
To learn about the processes of erosion and deposition.
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COASTLINES
Lesson starter:
You have been given a number of sort cards.
You must sort out the words to match with the definitions.
Some of the class will never have seen the terms before as they have
never studied coasts – but this is a great opportunity to learn.
Copy the word and definition once you are sure that it is correct.
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Hydraulic Action
COASTLINES
The force of waves
hitting a cliff (or
sea wall) compresses
water and air into
cracks and joints.
This increase in
pressure may lead to
cracks widening and
pieces of rock
breaking off.
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Corrasion
COASTLINES
Rock fragments may be
picked up by waves and
thrown against the rock face
of cliffs by subsequent
waves.
Sometimes the softer strata
are abraded more than the
harder ones, giving a striped
appearance.
Corrasion is most effective
at the base of cliffs.
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Wave attrition
COASTLINES
Rock fragments are worn
down into smaller and
more rounded pieces.
Currents and tidal
movements cause the
fragments to be swirled
around and to grind
against each other.
This type of erosion
produces pebble
beaches.
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COASTLINES
Water- layer weathering
Alternative wetting and
drying -as happens with
the rise and fall of the
tides -can disintegrate
porous or coarser rock
layers.
Salt crystals growing in
rock spaces can do the
same thing.
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Corrosion (solution)
Salts and acids in sea
water can react with
rocks , slowly dissolving
them away.
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COASTLINES
Rates of erosion depend on many
factors: (Copy this note into your jotters. Use your
LITHOSPHERE CORE
textbook to help add detail to each of the
headings.) 10 mins
Waves – strength, frequency,
height
Weather – frequency of storm
conditions
Geology of the coastline :
-type of rock
-orientation of stratification
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COASTLINES
The FETCH is the
distance travelled
by waves from one
shore to another.
The waves hitting
the southwest
coast of England
have a fetch of
about ten
thousand miles!
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CONSTRUCTIVE
AND DESTRUCTIVE
COASTLINES
WAVES
Constructive waves These are low energy waves which
transport grains of sediment and deposit them on beaches.
This type of wave is common in the summer.
Destructive waves These are high energy waves which
erode sediment from the beach and deposit material further
along the coast. They mainly occur during winter and
autumn storms.
Constructive and destructive waves
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SWASH AND BACKWASH
COASTLINES
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Waves break and push
sediment obliquely up the
beach (SWASH)…
… but the returning flow is
straight down the beach at
right angles to the shoreline
(BACKWASH) .
Swash and backwash
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COASTLINES
Quick Revision
After your work station task, you
should be able to answer the
following questions
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COASTLINES
Q1. What two properties of a headland tell us
that the rock is hard?
A. It juts out into the sea and is high ground.
Q2. What two properties of a bay tell us that
the rock is soft?
A. It eats back into the land and is lower ground.
Q3. On a new cliff coast, what is the first
feature caused by erosion?
A. Wave cut notches are created initially.
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COASTLINES
Q4.Cliff retreat creates which feature all along
the coast?
A. It creates a wave-cut platform.
Q5.Why is this only exposed at low tide?
A. Erosion only happens between high and low tide
marks, and no erosion takes place below LTM.
The ‘top’ of the eroded cliff is the WCP, seen
only when the tide is lowest.
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COASTLINES
Headland erosion near Noss Point
Caithness
The sea is eroding this headland back leaving a wavecut platform below the waves.
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COASTLINES
Cliffs and Wave Cut
Platforms
Wave cut platform
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Geo
A geo is a small, narrow, steep-sided
channel in a sea cliff.
It has been formed by erosion along a
line of weakness, such as a joint.
Originally it was a cave but, at various
stages the roof has collapsed, leaving
the inlet.
They are found in hard cliff coastlines
e.g. Northern Scotland
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Geo near Noss Point
Caused by hydraulic action at a
weakness in the rock.
Geo
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Geo At Duncansby Head
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A Blowhole or ‘gloup’ is a funnel shaped
depression, linking the cliff top
with the sea cave. Continued erosion of
a vertical joint at the back
of a sea cave may lead to
the collapse of the cave’s roof.
This usually happens at high
tide in stormy weather.
Copy this note
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COASTLINES
Clip on blowholes
Bullers of Buchan is an Scottish
Example of a blowhole. The
Feature is 50m deep!
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COASTLINES
Coves are a special feature and we will learn about
them by looking at a case study of Lulworth Cove.
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COASTLINES
Lulworth Cove was formed by differential
erosion. The next slides will explain how this
happened.
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COASTLINES
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The geology of Lulworth Cove
hard
soft
Copy the diagram
and explanation.
The hard rock at the
coast has been
breached. The sea
can now get in to
erode the softer rock
behind, creating the
cove. The second
layer of hard rock
stops the cove
growing much larger.
.
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COASTLINES
ORDNANCE SURVEY MAPWORK
You need to be able to recognise
coastal erosion landforms from a
map.
To practice this skill, take a copy
of the question sheet and the two
O.S. maps and tackle the questions.
THEY ARE NOT ALL EASY !!
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