Coasts Revision - Physical Processes

Revision of physical coast processes eg longshore drift, constructive and destructive waves etc

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  • Created by: caz
  • Created on: 24-12-10 16:33

Topics

- The characteristics of waves.

- How erosion and weathering shape the coastline.

- How rock type and structure influences coastal landforms.

- How to describe the landforms associated with ‘hard’ and ‘soft’ coastlines.

- How waves move beach sediment.

- How the deposition of beach sediments creates coastal landforms.

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Key Words

Coast - where the land meets the sea

Waves - the wind pushing the water

Crest - top of a wave

Trough - bottom of a wave

Marine Erosion - wearing away of rocks by the action of the sea

Weathering - breaking down of rocks by weather, plants or chemical action


 

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Key Words

Prevailing Wind - the dominant wind in an area

Swash - movement of water travelling up the beach

Backwash - movement of water travelling away from the beach

Fetch - distance the waves have travelled 

Constructive wave - a wave with a stronger swash 

Destructive wave - a wave with a stronger backwash

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Landforms of Hard Coastlines

- Headlands and Bays

- Caves

- Arches

- Stacks 

- Stumps

- Wave cut platfoms 

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Retreat of Soft Coastlines

Slides - material shifts in a straight line 

Slumps - material shifts with rotation

Rockfalls - material shifts vertically

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Formation of Bays and Headlands

(http://t3.gstatic.com/images?q=tbn:ANd9GcQnm-o35KQ09M0IbJqgchbrWQKEzTU3bmyIg0TL0VtJwqZULUOA)(http://t0.gstatic.com/images?q=tbn:ANd9GcS1ks3yDYWnJy_KIilTM1oT2U60LU5ZRghP79P404uvEuVC2g4f)

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Erosion of Headlands

- Headlands are usually made of resistant rocks, but they have weaknesses like cracks

Waves crash into the headlands and enlarge the cracks - by hydraulic action and abrasion 

- This causes a cave to form

- Continued abrasion deepens the cave until it breaks through and forms an arch


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Erosion of Headlands

- Erosion continues to wear away the rock which supports the arch until it collapses

- This forms a stack - an isolated rock that's seperate from the headland, like Old Harry

- The stack is worn down to form a stump, like Old Harry's Wife

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Constructive Waves

- Shallow and widely spaced apart

- Small in height and low in energy

- Movement up the beach (swash) is strong

- Carry material up the beach creating depositional landforms

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Destructive waves

- Steep, close together and quick breaking

- Large in height and high energy

- Strong backwash

- Remove (erode) material from the beach creating erosional landforms

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Erosion Processes

Corrasion/abrasion - where the water gradually wears away the surface of the rock stores

Attrition - rocks are smashed together and made into smaller pieces by waves and their edges are rounded off

Corrosion - the weak carbonic acid in the sea water dissolves rock like chalk and limestone

Hydraulic action - the force of the water against rocks makes cracks appear and eventually bits of rock break off

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Longshore Drift

(http://t3.gstatic.com/images?q=tbn:ANd9GcR5mIBuBYzuCWbtlBWm2sTzvBWyPd1eizWQ5uBhE6d8-GxL7L8_)

Landforms caused by Longshore Drift -

Spit - forms at sharp bends when sand and shingle are carried past the bend and deposited, strong wind then forms the curve

Bar - a spit which joins two headlands together and cuts off the bay, a lagoon then forms behind the bar

Tombolo - a bar which connects the shore to an island eg Chesil Beach

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Coastal System

Erosion/Weathering - Transportation - Deposition

The coastal system acts like a conveyer belt. Material is worn away from some places, then moved by waves and deposited in other places.  

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Case Studies

Headland and Bay - The Foreland and Swanage Bay in Dorset

Arch - Durdle Dorr

Stack and Stump - Old Harry and his Wife

Spit - Spurn Head or Hurst Castle 

Tombolo - Chesil Beach in Dorset which joins to the Isle of Portland

Lagoon - The Fleet lagoon (behind Chesil Beach) 

 

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