Coastal processes, patterns and associated landforms EROSION FOR WEB.pdf · •Landforms of coastal...
Transcript of Coastal processes, patterns and associated landforms EROSION FOR WEB.pdf · •Landforms of coastal...
Coastal processes, patterns and associated landforms
Coastal processes and the impact of recreational pressures,
coastal defence work, conservation and management measures
Coastal Processes, Patterns and
Associated Landforms, and
Human Interaction
• Waves
Responsible for erosion, transportation and deposition of material
along coastlines
Generated by wind passing over the surface of the sea
Fetch is the open area of the sea that a wave travels over
The longer the fetch, the stronger the wind speed, the stronger and
greater the waves generated
• Factors affecting the rate of coastal erosion
Where the breaking of a wave occurs
1. Steepness of the wave – greater erosion
2. Rock resistance – soft rock = greater erosion –
chalk - limestone
3. hard rock = less erosion - granite
• Types of waves
1. Constructive waves
2. Destructive waves
Constructive Waves – gentle wave
action – deposition of material –
features formed
Destructive wave action –
strong – storm waves –
destruction of coastal areas –
erosional features formed
Constructive waves
Destructive waves
• Wave refraction
Waves slow down as water becomes shallow
Waves bend and change their direction as they approach the shore
Causes waves to move towards the headland where their erosive force
is released
Coastal Erosion
• Processes of coastal erosion
Hydraulic action – force of the water
Air Compression – air in waves
Abrasion/corrosion – pebbles in waves act like
sandpaper
Attrition – pebbles hit off each other and
become rounded
Solution/corrosion- salt/ minerals in sea water
dissolve soft rock
DIAGRAM OF CLIFF FORMATION
The feature of
coastal erosion I
have studied is a
wave built terrace
– wave cut
platform
An example of this is found at
the Cliffs of Moher, Co. Clare
• Landforms of coastal erosion
1. Cliffs
Cliffs are vertical slopes on a coastline
Form as a result of a combination of coastal processes of
erosion, such as hydraulic action, compression, abrasion,
solution and attrition
Destructive waves attack an area of weakness in rocks
Crack/joint forms
Crack/joints are attacked by hydraulic force of the water and by
compression
Notch forms
• Landforms of coastal erosion
1. Cliffs (continued)
Notch gets bigger, eventually the rocks above the notch are unsupported and collapse to form a cliff
Shattered rock falls into the sea
Sea uses this shattered rock to further erode the cliff through abrasion
Solution also erodes the cliff face
These events continue over time and the cliff face retreats
Wave-cut platforms – surface of rock that remains in front of the retreating cliff
Wave-built terraces – deposited pieces of rockthat are deposited below low-tide level
• Landforms of coastal erosion
2. Bays and headlands
Differential erosion – rocks along coastlines
are eroded at differing rates depending on
whether they are soft or hard
Sections of coastline that are composed of
soft rock will erode faster than areas
composed of hard, more resistant rock
Stretches that are composed of soft rock will
form bays
Harder more resistant rock will take longer to
erode and will remain jutting out into the sea
as headlands
• Landforms of coastal erosion
3. Sea caves, sea arches, sea stacks and sea stumps
Caves form in an area of weakness on a cliff face or
headland
Processes of coastal erosion act on this area of
weakness and enlarge it to form caves
Caves are further eroded by abrasion, resulting in
them becoming larger
Sea arches form when continued erosion occurs in a
sea cave causing it to extend right through the
headland
A sea arch may also form when two sea caves form
back to back on the opposite sides of a headland
A sea stack is a rock which is standing out in
isolation in the sea away from the coastline
DIAGRAM OF CAVE, ARCH AND STACK FORMATION
Doolin, Co. Clare
Causeway coast,
Antrim
Sea Arches
3. Sea caves, sea arches, sea stacks and sea stumps
Sea stacks form when erosion continues on a sea
arch, widening the sea arch and causing the roof
of the sea arch to eventually collapse
When the roof of the sea arch collapses, it leaves
the former section of headland isolated or cut
away from the main headland/coast. What
remains standing out in the sea in isolation is called
a sea stack
A sea stump is the eroded remains of a sea stack
Landforms of coastal erosion
Coast of Victoria,
Australia
American
coast
Old Man of Hoy,
Orkney Islands
Downpatrick Head
Co. Mayo
• Landforms of coastal erosion
4. Blowholes
Blowholes form at areas of weakness, for example, where a hole
forms on the surface of a cliff top joins with a roof of a sea cave.
They are formed as a result of compression
Air may become trapped in a sea cave by waves
Results in a build up of pressure which leads to rock shattering the
rocks of the cave roof
Rock eventually collapses
creating a ‘blowhole’