Coastal Coastal FeaturesFeatures

Higher GeographyHigher Geography

LithosphereLithosphere

‘ ‘ A recent estimate of the A recent estimate of the coastline of England and wales coastline of England and wales

is 2750 miles and it is very is 2750 miles and it is very rare to find the same kind of rare to find the same kind of

coastal scenery for more than coastal scenery for more than 10 to 15 miles together’10 to 15 miles together’

J.A. Sheers, The Coastline of England and Wales, J.A. Sheers, The Coastline of England and Wales, 19691969

IntroductionIntroduction

• For its size, Scotland has a very long For its size, Scotland has a very long coastline.coastline.

If you straightened out all of the bends and twists, you would have coastline

about 10, 000km long.

MapMap

• The west coast of The west coast of Scotland has Scotland has more inlets and more inlets and sea lochs than sea lochs than the east and the east and tends to be more tends to be more rugged.rugged.

WavesWaves

WavesWaves• Waves are caused by the wind dragging Waves are caused by the wind dragging

on the surface of the water. The length of on the surface of the water. The length of water the wind blows over is called its water the wind blows over is called its fetchfetch..

When waves reach the coast When waves reach the coast (1)(1)

• Out at sea, the Out at sea, the waves roll. In a waves roll. In a gale they can be gale they can be over 30m high!over 30m high!

The sea kayak is 4m long

The sea kayak is 4m long

The sea kayak is 4m long

• They break in They break in shallow water. The shallow water. The water that rushes water that rushes up the sand is up the sand is called the called the swashswash..

When waves reach the coast When waves reach the coast (2)(2)

When waves reach the coast When waves reach the coast (3)(3)

• The water rolling The water rolling back into the sea back into the sea is called the is called the backwashbackwash. .

Backwash

The waves at workThe waves at work

Waves have energy. That Waves have energy. That means they can work. They means they can work. They

work non-stop, night and day work non-stop, night and day shaping the coastline.shaping the coastline.

ErosionErosion Waves erode in the same way as rivers

Human ActivityHuman Activity

• The increase in pressure resulting The increase in pressure resulting from building on cliff tops and the from building on cliff tops and the removal of beach material which removal of beach material which may otherwise have protected the may otherwise have protected the base of the cliff both contribute to base of the cliff both contribute to more rapid coastal erosion.more rapid coastal erosion.

TransportTransport

DepositionDeposition

• Waves continually carry material on Waves continually carry material on and off the land. If they carry more and off the land. If they carry more onon than than offoff – a beach forms! – a beach forms!

• Some beaches are made of sand. Some beaches are made of sand. Some are made of shingle or small Some are made of shingle or small pebbles.pebbles.

Coastal LandformsCoastal Landforms

Old Harry Rocks in Dorset

Coastal LandformsCoastal Landforms

• Coastal landforms include:Coastal landforms include:– Wave cut platformsWave cut platforms– Coves & BaysCoves & Bays– Sea archesSea arches– Sea stacks and stumpsSea stacks and stumps– SpitsSpits

IntroductionIntroduction

• Day and night, the waves are hard at Day and night, the waves are hard at work. They work. They erodeerode parts material parts material from some parts of the coast and from some parts of the coast and depositdeposit it in other parts. it in other parts.

• The coast is made of hard and soft The coast is made of hard and soft rock and over time it makes various rock and over time it makes various landformslandforms..

This coastlines is made of different rock types, some hard, some soft. Once upon a time it was straight.

This coastline consists of parallel bands of hard and soft rock which were perpendicular to the sea.

As a result of differential erosion, the bands of soft rock are eroded

much more quickly than the bands of resistant rock to form bays and

headlands.

The headland is eroded back as a result of wave refraction. Caves, arches, stacks and stumps will form which will eventually be eroded away. The bays will advance as deposition will take place at their heads to form Beaches.

Eventually, the coastline will become straight again and the whole process of differential erosion will start again and result in an irregular coastline.

Differential rates of erosion along a coast with alternate bands of hard and soft rocks results in an irregular coastline - Headland and Bay.

As waves enter the shallow waters of the headland, the influence of the shallow waters causes the wave fronts to bent and get refracted. Due to the wave refraction, wave energy is more concentrated towards headlands and dissipated towards bays.

Marine processes - hydraulic action and corrosion erode along lines of weakness (e.g. joints, faults and bedding planes).

Continuous erosion causes back-to-back caves to extend backward until the sea caves meet and a natural tunnel is formed.

When the arch collapses, the sea ward pillar is left standing and becomes a stack. Continual wave erosion eventually reduces the stack into a stump.

The top portion of the sea caves becomes an arch, linking the tip of the headland with the mainland.

How caves, arches and stacks How caves, arches and stacks form (1)form (1)

• The sea The sea attacks attacks cracks in the cracks in the cliff at the cliff at the headwall. headwall. The cracks The cracks grow larger – grow larger – and form a and form a cavecave..

How caves, arches and stacks How caves, arches and stacks form (2)form (2)

• The cave gets eroded The cave gets eroded all the way through. It all the way through. It turns into an turns into an archarch. . Then one day …Then one day …

How caves, arches and stacks How caves, arches and stacks form (3)form (3)

• … … the arch the arch collapses, leaving a collapses, leaving a stackstack. In time, the . In time, the waves erode the waves erode the stack to a stack to a stumpstump..

CovesCoves

Lulwoth Cove, Dorset

Stair Hole

Lulworth Cove

Stair Hole

Lulworth Cove

The Lulworth coast was once a solid cliff with a stream running down to the sea

Cove formation (1)Cove formation (1)

Once breached, the softer cliffs behind were rapidly eroded

Cove formation (2)Cove formation (2)

Cove formation (3)Cove formation (3)

This process continues for many years

Lulworth today

Lulworth tomorrow!

The next Durdle Door could well form between Lulworth Cove and Stair Hole

The future?The future?

Old Lulworth Cove?

Old Stair Hole?

Place of old arch?Sea Stump

Could Lulwoth become like Manowar Cove, Dorset Coast?

Wave Cut PlatformsWave Cut Platforms

Destructive waves at an exposed coast erode a steep coastal slope through processes like hydraulic action and abrasion.

The waves erode along lines of weakness in the rock face to form a notch.

Continued erosion enlarges the notch and causes its roof to collapse, and a cliff is formed.

Further undercutting at the base of the cliff results in an overhanging cliff which eventually collapses.

As the steep cliff retreats landwards, a flat terrace at the foot of the cliff is exposed - wave-cut platform.

The eroded materials which are transported away may be deposited in the sea to form an offshore terrace.

http://www.stacey.peak-media.co.uk/Harry/800Harry8.jpg

Coastal SpitsCoastal Spits

Coastal spitsCoastal spits

• Spits are long, narrow accumulations Spits are long, narrow accumulations of sand and/or shingle with one end of sand and/or shingle with one end joined to the mainland and the other joined to the mainland and the other projecting out into the sea.projecting out into the sea.

• Sandy are formed by Sandy are formed by longshore longshore driftdrift..

Directi

on of longsh

ore drif

t

The end of spit is curved by the waves

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