Transcript The Restless Earth

Key terms
Key term
Definition
Weathering
The process whereby rock is broken down due to weather or plants /
animals.
Erosion
The wearing away of rock.
Hydraulic action
Water and air are forced into cracks in rock, breaking it apart.
Abrasion
When rocks and pebbles rub against a cliff, wearing it away.
Attrition
When rocks and pebbles crash into each other and break apart.
Solution
Chemicals in sea water dissolve rock.
Transportation
The movement of material in water.
Deposition
When material is dropped by the water, due to decreased energy.
Erosional landform
A landform created by erosion.
Depositional
landform
A landform created by deposition.
Concordant coast
A coastline where the rock layers are parallel to the sea.
Discordant coast
A coastline where the rock layers are at right angles to the sea.
Mass movement
The movement of large amounts of material when a cliff collapses.
Slumping
Mass movement of soft rock clifs
Key terms
Key term
Definition
Rockfall
Mass movement on hard rock cliffs.
Wave-cut platform
A wide, flat expanse of rock left behind after a rockfall.
Arch
An erosional landform formed when the sea erodes through a
headland.
Stack
A tall column of rock left behind after an arch collapses.
Stump
A short column of rock left behind after a stack collapses.
Headland
A section of coastline, often formed of hard rock, which projects out
into the sea.
Bay
An inlet, often formed from the erosion of soft rock, between two
headlands.
Spit
A depositional landform which projects out across an inlet from a
headland
Tombolo
A depositional landform connecting the mainland to an island.
Bar
A depositional landform connecting two headlands.
Swash
The movement of a wave up the beach after it has broken.
Backwash
When a wave washes back down the beach at right angles due to
gravity.
Key terms
Key term
Definition
Amplitude
The height of a wave.
Wavelength
The length of a wave.
Crest
The ‘top’ of a wave.
Trough
The ‘bottom’ of a wave.
Constructive wave
A wave with a long wavelength and low amplitude, which has a strong
swash, building up a beach (Summer wave).
Destructive wave
A wave with a short wavelength and high amplitude, which has a
strong backwash, eroding a beach (Winter wave).
Fetch
The distance between two pieces of land, which wind blows over.
Prevailing wind
The most common wind direction.
Beach profile
The shape of a beach.
Longshore drift
The movement of material along a coastline.
Tide
The rising and falling of the sea due to the moon’s gravitational pull.
Storm surge
When a particularly high tide (‘spring’ tide), coupled with
exceptionally low pressure, causes a bulge in the sea, flooding coastal
areas.
Key terms
Key term
Definition.
Emergent coast
An ‘old’ coastline, which is raised above the current sea level, due to a
fall in sea levels.
Hard engineering
Man-made, structural coastal protection methods, designed to reduce
or absorb wave energy, or interrupt longshore drift.
Soft engineering
Management methods designed to work with nature and mimic
natural forces.
Key facts: Erosion and Weathering
Types of erosion:
1. Hydraulic action
Water and air are forced into the cracks in the rock, which
helps break the rock up.
2. Solution
Sea water dissolves soluble minerals in the rock.
3. Abrasion
Sandpaper effect – sand, pebbles and stones wear away the
rock as they scrape against it.
4. Attrition
Pebble to sand – chunks of rock have been knocked
together and worn into smaller and smaller pieces.
Types of weathering:
Freeze-thaw:
• Rain water enters crack in rock
• When temperature falls below
freezing, water freezes and expands
• Ice then melts and contracts
• Continued expansion and
contraction forces rock apart
Biological:
• Seeds fall into crack in rock
• Tree roots grow
• As roots get bigger and thicker,
they force the rock apart
• Biological weathering also
includes burrowing animals
Key facts: Hard and soft rock cliffs
Hard
• High, steep and rugged
• Cliff face often bare, with little or
no vegetation
• Not easily eroded
• Large boulders and rocks at the
bottom of the cliff
• Mass movement occurs as
rockfalls
Soft
• Less steep, sloping cliffs
• Often made of soft clay
• Easily eroded
• Vegetation often grows on the
slope
• Mass movement occurs as
slumping
Key facts: Discordant coasts
 DISCORDANT coasts are made up of both hard and soft
rocks. Hard rocks stick out as HEADLANDS and the soft
rocks are easily eroded and form BAYS. At discordant coasts
these different rock types are at right angles to the coast.
Chalk - hard
Clay - soft
Limestone - hard
Clay - soft
Limestone - hard
Headland
Bay
Headland
Bay
Headland
Key facts: Concordant coasts
 CONCORDANT coasts occur where the bands of hard and
soft rock are PARALLEL to the coast, which forms a coast of
high cliffs and small coves. At Lulworth Cove in Dorset, a
small bay (cove) has formed where hydraulic action and
abrasion have ‘punched’ through the band of hard rock and
eroded the soft rock behind it.
Hard, resistant chalk
Soft sand and clay
Fairly resistant limestone and
shale
Hard, resistant Portland
Limestone
Key facts: Wave-cut platforms (erosional
landforms)
This process repeats, so the cliff
slowly retreats backwards, making
the wave-cut platform longer and
longer.
This leaves a wave-cut platform; a wide,
flat expanse of rock which is exposed at
low tide
This develops into an overhang,
which can no longer support
itself and eventually collapses.
The loose rock (debris)
eventually gets washed
away by backwash and
eroded by the waves
This causes a wave-cut notch to
form, which gradually gets bigger.
Waves cause undercutting at
the base of the cliff.
Key facts: Caves, arches, stacks and stumps (erosional
landforms)
Key facts: Constructive (summer) waves
 In the summer waves are gently sloping (have a low
amplitude) and have a long wave length (meaning there
are long gaps between each wave). The swash is strong,
causing sand to be pushed up the beach and deposited.
This results in the beach building up, but having a
shallow profile.
Key facts: Destructive (winter) waves
 In the winter waves are steeply sloping (have a high
amplitude) and have a short wave length (meaning there
are shorter gaps between each wave). The backwash is
strong, causing sand to be pulled down the beach and
eroded. This results in the beach erosion, with a steep
profile
Key facts: Longshore drift
Longshore drift is the movement (transport) of material
along the coast
Key facts: spits (depositional feature)
Key facts: tombolos (depositional feature)
Key facts: bars (depositional feature)
Key facts: Sea level rise
• It is widely regarded by
scientists that sea levels are
rising
• Estimates range from 30cm
to 1m by the year 2100
• Many low-lying areas
around the world are at risk,
for example the Maldives,
Bangladesh and the
Netherlands
• The UK is not exempt from
this, many areas of the UK,
especially in the South and
East are at real risk from sea
level rise.
Key facts: Storm surges
•Powerful winds push water
towards coast
•Low pressure forces bulge in
sea surface, which creates a
surge when fanned by the
winds
•Sea levels will rise by about
1cm for every 1 millibar
decrease in pressure
•A depression of about
960mb - about 50mb less
than average barometric
pressure - would raise sea
levels by about half a metre
•If there is a high tide at the
time the resulting waves
could breach even sound
coastal defences. A storm
surge coinciding with a
spring tide could lead to
widespread flooding
Key facts: Problems caused by coastal erosion
Loss of farmland
Damage to property
Danger to tourists
Loss of infrastructure
Conflicts can occur between different groups. You will need to say WHY these
conflicts can occur:
Residents
Farmers
Business owners
Local government
National government
Conservationists
Tourists
Key facts: Hard engineering
More traditional method of coastal defences
used to stop or absorb the wave energy
They are usually expensive and ugly
They tend not to be sustainable, as they can
cause damage further down the coast
YOU WILL NEED TO KNOW THE COSTS
AND BENEFITS OF EACH METHOD
Rock armour
Groynes
Gabions
Sea wall
Revetments
Offshore reef
Key facts: Soft engineering
Less traditional method of coastal defences
Attempts to work with natural forces, i.e.
wave energy, and mimic natural techniques
Usually cheaper, more attractive and
sometimes self-sustainable
YOU WILL NEED TO KNOW THE COSTS
AND BENEFITS OF EACH METHOD
Cliff stabilisation
Beach
replenishment
Named examples of coastal landforms.
Feature
Location
Concordant coast
Coastline around Lulworth
Cove and Durdle Door,
Dorset.
Discordant coast
Swanage Bay, Dorset
Wave-cut platform
Kimmeridge Bay, Dorset
Cave, arch, stack and stump
sequence
Old Harry Rocks, Dorset
Spit
Dawlish Warren, Devon
Tombolo
Chesil Beach, Dorset
Bar
Slapton Sands, Devon
Named example: Climate change effects on the UK
Named example of an area affected by coastal
erosion and retreat: Holderness, East Yorkshire
Mappleton
Situated approximately 3km
south of Hornsea lies the village
of Mappleton. Supporting
approximately 50 properties,
the village has been subject to
intense erosion at a rate of 2.0m
per year, resulting in the access
road being only 50m from the
cliff edge at its closest point.
The cliffs are made of soft clay
and are subjected to a number
of storms in the Winter months,
as well as saturation from heavy
rainfall.
Mappleton today:
Rock armour
Cliff stabilisation
BUT the groyne has led to
increased erosion further down
the coast, as beaches further
south are no longer being
supplied with material from
longshore drift.
Rock groyne
Past Questions
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Name the physical process that moves beach material along the coastline (1 mark)
Name and describe one process of coastal erosion. (2 marks)
Describe how cliffs such as this have collapsed. (2 marks)
Outline one difference between cliffs on soft rock and hard rock coasts (2 marks)
Identify two differences between constructive and destructive waves. (2 marks)
Using named examples, explain the costs of two different methods of coastal management.
Explain why some waves erode more than others (2 marks)
Describe one possible consequence of climate change on coastal erosion (2 marks)
Describe how a wave cut platform is formed (2 marks)
Explain how a spit is formed. You may use a diagram to help with your answer. (6 marks)
Describe the process of longshore drift. You may use a diagram to help with your answer. (3
marks)
Examine the difference between concordant and discordant coasts (8 marks)
Explain how physical processes can cause coastal retreat. (6 marks)
For a named location, describe the problems caused by coastal retreat (6 marks)
Name one economic consequence of coastal erosion (2 marks)
For two different types of sea defence explain how they reduce erosion (6 marks)
Explain how the rate of coastal erosion can be managed (6 marks)
For a named location, explain the costs and benefits of using hard engineering techniques to
protect a coastline from erosion. (6 marks)
Using examples, explain the benefits of using modern holistic (wide ranging)
approaches to coastal management. (6 marks)
For a named coastline, examine why there are conflicting views about how coastal erosion should
be managed (8 marks)
For a named area of coast, explain how coastal retreat is being managed. (6 marks)
For a named coastline, explain how it is managed (6 marks)
Using a named coastline, explain how both hard and soft engineering are used to manage it (6
marks)