Coasts

Juliette GRISONI

Table of contents

• Presentation ( title page)

• The costal system

• Coastal erosion :• -Hydraulic action • -Abrasion• -Attrition• -Solution

• Caves, arches, stacks, stumps : • - How are caves formed.• -How are arches formed.• -How are stacks formed.• -How are stumps formed.

• Why are coasts important ?

• Bibliography and credits.

The coastal system Inputs

1. Marine - Waves- Tides- Solution 2. Atmosphere- Sun - Precipitations- Air pressure- Wind speed&direction3. Humans- Pollution- Recreation- Settlements- Defences4. Terrestrial - Weathering- Erosion- Deposition- Rock structure & type

Outputs • Beaches• Sand dunes• Spits• Tombolos• Headlands and bays• Wave cut notches• Wave cut platforms• Caves• Arches• Stacks• Stumps• Cliffs • Reefs

Processes

1. Erosion

2. Transport

3. Deposition

Coastal erosion • The sea shapes the coastal landscape. Coastal erosion is the wearing away and breaking

up of rocks along a coast. Destructive waves erode the coastline in a number of ways.

• Vocabulary : • -Destructive wave : Destructive waves are created in storm conditions and from big, strong waves; when the

wind is strong and has been blowing for a long time. They occur when when there is a high wave energy and when the wave has travelled over a

long fetch (distance).They tend to erode the coast (frequently).They have a stronger backwash than swash.They have a short wave length, they are high and steep.

Wave breaks, water is washed up the beach= swash.Water runs down the beach= backwash.

Hydraulic action

• Air may become trapped in joints and cracks on a cliff face. When wave breaks, the trapped air is compressed which weakens the cliff and causes erosion.

Abrasion/corrasion

• Abrasion is bits of rock fragments and sand in waves that grind down cliff surfaces and cause erosion.

Attrition

• Attrition is when waves smash rocks and pebbles on the shore into each other, they break and become smoother.

Solution

• The acids contained in sea water will dissolve some types of rocks such as chalk or limestone.

Caves, arches, stacks, stumps

• Weathering and erosion can create caves, arches, stacks and stumps.

Caves

• Caves occur when waves force their way into cracks in the cliff. The water contains sand and other materials that grind the rock until the cracks become a cave. Hydraulic action is the predominant process in the creation of a cave.

Riko Riko cave : New Zealand, Poor knights islands

Arch

• If the cave is formed in a headland, it may eventually break through the to the other side forming an arch.

London arch : Victoria (right)Cabo San Lucas arch : Mexico (left)

Stack

• The arch will gradually become bigger until it can no longer support the top of the arch. When the arch collapses, it leaves the headland on one side and a stack (a column of rock) on the other.

Old Harry rocks2 chalk stacks in Southern England, Dorset .

Stump

• The stack will be attacked at the base in the same way that a wave cut notch is formed. This will weaken the structure and it will eventually collapse to form a stump.

Salton sea stumps

Cliff

Cave

Arch

Stack

Stump

Why are coasts important ?

• They are economic sites for industries and fishing, trading etc…

• They are habitats and ecosystems.• They are a benefit for tourism and recreation. • They protect and defend our coast from being

flooded.

Bibliography and credits

• http://en.wikipedia.org/wiki/Coastal_erosion• http://www.caverider.co.nz/rikoriko.htm• http://geobytesgcse.blogspot.com/2007/08/c

oastal-processes-erosion-transport-and.html• http://answers.askkids.com/Nature/types_of_

coastal_erosion• http://answers.yahoo.com/question/index?qi

d=20090629110030AAG84aw