Geography Paper 1 (1.2)

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  • Created on: 01-05-16 16:05

Waves

How waves are formed

Out at sea, the wind tugs at the surface of the water, causing the wave shape to move, when the wave moves into shallow water near the coast it is distorted until it 'breaks' then the water moves forward, water rushing up the beach is called the swash and when the water drains back down the beach is called the backwash

Size of a wave

How strong the wind is

How long it blows for

How far it travels

The distance the wind blows over is called a fetch

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Wave Types

Destructive waves

The waves have a weak swash and a strong backwash pulling sand and pebbles back down the beach. These are destructives because they remove material from the beach. The characteristics of these waves are steep, high waves that are close together and crash down onto the beach.

Constructive waves

The waves have a very strong swash and a weak backwash as they push sand and pebbles up the beach and leave them behind when the water retreats because the wave isn't strong enough to remove them. They are low waves with gaps between them.

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Coastal Erosion

Hydraulic Action - Water forced into the cracks in the rock, compressing the air inside so when the wave retreats, the compressed air blasts out and can force the rock apart.

Abrasion - Loose rocks are thrown againist the cliff by the waves and wears the cliff away and chips rock off

Attrition - Loose sediment knocked off the cliff by hydraulic action and abrasion is swirled around by the waves and collides with other sediment leading to the sediment getting smaller and smaller

Solution - When seawater dissolves material from the rock, it happens along limestone coasts where calcium carbonate is dissolved

Landforms by erosion

Wave-cut notch - Waves hit the bottom of the cliff, eroding a wave-cut notch. The cliff above the notch is undercut and the overhanging rock eventually falls, leaving the steep cliff face.

Wave-cut platform - As the cliff errodes it leaves behind flat rocks and rock pools.

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Coastal Erosion 2

Headlands and bays

Where coasts are formed from alternating bands of hard and soft rock. The less-resistant rock will form bays. The more-resistant rock will form headlands.

Caves, arches and stacks

A joint or fault in resistant rock appears, abrasion and hydraulic action widen the joint to form a cave. Waves make the cave larger until it cuts through the headland to form a arch which is eroded so the roof collapses as it becomes to heavy. This leaves a tall stack which is eroded and collapses, leaving a stump

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Coastal Transport

Methods of transport

Suspension - Fine sediment is carried as a suspension in the water making it look muddy or murky

Solution - Dissolved material is carried along in solution, so you can't see it

Traction - Larger pebbles and cobbles are rolled along the sea bed

Saltation - Small pebbles are moved when one pebble hits another, causing it to bounce. The bouncing can cause a chain reaction

 Longshore drift                                                                                                             Waves approach the beach at a slight angle, as the waves break, the swash carries material  up the beach at the same angle as the wave approached, as the swash dies away the backwash and any material carried by it falls straight back down the beach under the influence of gravity meaning the material has moved along the beach in a zig-zag route. To prevent longshore drift we build wooden or rock fences called groynes to trap the sediment and stop the transportation along the coast

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Coastal Deposition

Spits

Spits are long narrow ridges of sand and shingle stretching out from the coast. They form where longshore drift moves sediment along the coast in the direction of the prevailing wind. When the coastline changes direction, such as at the mouth of a river, the sediment is then deposited as a long ridge, which streches away from the coast to form a spit

Bars

Bars are narrow ridges of sand and shingle that grow across a bay as a result of longshore drift. They can trap lagoons behind them. The lagoon may fill up with sediment eventually. Sometimes storm waves sometimes crash over the top or break through a bar. 

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Collapsing Cliffs

Why do cliffs collapse?

Marine processes - The base of the cliff is eroded by hydraulic action and abrasion making the cliff face steeper

Sub-aerial processes - The cliffs are attacked by weathering, loosening the rocks causing them to fall or slide because of gravity

Types of weathering

Mechanical weathering - (Freeze-thaw) When temperatures drop below freezing at night and rise during the day, so the water in the cracks freeze and expands then thaws again which repeats again and again until the rock is weakened and fragments break away

Chemical weathering - (Solution) When water reacts with the calcium carbonate in the rocks e.g. limestone so the calcium carbonate dissolves and is washed away in solution, weakening the rock

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Mass Movement

Sliding

When large chunks of rock slide down the slope quickly without any warning, making it very dangerous to walk along the bach under the cliffs

Slumping

Where cliffs are made of clay, the clay becomes saturated during heavy rainfall and oozes down towards the sea as part of a mud or debris flow

Human actions making it worse

Builiding on top of unstable cliffs can put pressure and weight on them adding to the chances of cliff collapse

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Cliff Collapse - Holderness Coast

One of the fastest eroding coastlines in Europe

1.8m of land is lost every year e.g. Great Cowden

Reasons for rapid erosion

Easily eroded rock type - the cliffs are made up of clay so its likely to slump

Naturally narrow beaches - beaches slow waves down reducing their power but narrow beaches give less protection

People worsening the situation - groynes have been built at mappleton which stop the material being moved down the coast, so some of the coast having no sediment to protect the cliff face

Powerful waves - Holderness faces the prevailing wind which brings waves from the north east (across the arctic ocean) which is a large distance so the waves gain more power so the coast is battered by highly erosive waves

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Cliff Collapse - Holderness Coast 2

Impacts on lives

Homes near cliffs e.g. Skipsea are at risk of collapsing into the sea

Property prices have fallen sharply along the coast as the houses are at risk

Some settlements are not accessible because roads have collapsed into the sea

Businesses are at risk and people will lose their jobs e.g. seaside caravan park looses 10 pitches a year

The gas terminal at Easington is at risk as its near the cliff edge, this terminal powers 25% of Britain's gas supply

80,000m of farmland is lost each year, having a large effect on farmers lives

Environment impacts - the lagoons near Easington are part of the SSSIs (Sites of Special Scientific Interest) If the bar erodes it will connect the lagoon to the sea, destroying it

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Rising Sea Levels - Maldives

A small island located in the Indian Ocean with the highest point of the land being 2.4m above sea. Tourism provides 30% of the Maldives GDP

What is happening?

Sea levels are rising and islands in the Pacific Ocean are beginning to disappear. Why? Scientists believe global warming and as the global temperature rises:

The polar ice sheets and mountain glaciers around the world are melting leading to more water in the sea

The water in the sea gets warmer and expands

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Rising Sea Levels - Maldives 2

Impacts on Maldives

Coral reefs will die as they're bleached and the water gets deeper

The ecosystem associated with the reefs will be lost

People will be forced to leave their homes and become environmental refugees

The traditional way of life will be lost

An end may come to the tourism industry

The country might disappear underwater

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Managing The Coast - Hard Engineering

Hard engineering - physical structures

Sea wall - Concrete structures which absorb the wave energy and provide a promenade for tourists. Costs £2000 per metre and is a pernament structure that will last for many years

Groynes - Long wooden or rock fences built out into the sea to stop longshore drift and help build up sand on one side. Costs £2000 per metre and stops the transportation of sediment

Rock armour (Rip-rap) - Large boulders piled up at the foot of the cliffs to absorb the energy of the waves and prevent them eroding the cliff. Costs £300 per metre and looks natural

Gabions - Rocks or boulders held in wire mesh cages and used to protect vulnerable areas from destructive waves. Costs £100 per metre and is the cheapest option

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Managing The Coast - Hard Engineering 2

For hard engineering

Local people - homes

Local tourist businesses - caravan parks and hotels

Local politicians - support residents and businesses

Againist hard engineering

Local taxpayers - who don't live on the coast

Environmentalists - fear natural habitats and beauty will be affected

People who live down drift - lose their beach

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Managing The Coast - Soft Engineering

Beach nourishment - building up beaches by adding more sand infront of the cliffs. It's natural protection as it absorbs wave energy

Sand dune regeneration - allowing sand dunes to building up around wooden structures. Sand dunes absorb wave energy and create new habitats

Salt marsh creation - allowing the sea to flood and spread over a large area creating a salt marsh. New habitats are created and it reduces the risk of flooding along the coast

Managed retreat - Abandoning the exisitng sea defences and building new ones further inland, creating a salt marsh which also floods in storm conditions. Some people will lose land, homes, businesses but new habitats are created and flooding is reduced in other areas

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Shoreline Management Plans

There are four main options:

Advance the line - build new, higher and better defences and protect land that is valuable

Hold the line - keep up and improve the exisiting defences

Do nothing - let nature take its course, so erosion takes place but new land is also built up elsewhere

Managed retreat - allow certain areas to flood, so that some areas are protected and some areas are not

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Coastal Habitats - Studland Bay Nature Reserve

It has a unique ecosystem - the relationship between plants animals and the environment

Issues

The nature reserve is a vulnerable environment, it took many years to establish and if the habitat is destroyed the ecosystem will break down

The nature reserve is home to rare species of plants and birds

The area attracts many tourists and the beach can get very crowded in the summer

Visitors need somewhere to park, plus other facilities such as toilets and paths

Visitors bring problems such as litter and create fire hazards e.g. cigarette ends

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Coastal Habitats - Studland Bay Nature Reserve 2

Solutions

Vulnerable areas and those recently planted with marram grass have been fenced off

Bird-watching hides and guided walks to help visitors to enjoy the wildlife properly

Car-parking spaces are limited and people are not allowed to drive on the beach

Boardwalks have been laid through the dunes to keep tourists on specific paths

Fire beaters have been placed in the dunes incase of fires

Jet skis are not allowed to be launched from the beach and there is a 5mph speed limit to reduce noise

Dogs aren't allowed on the middle beach from July to September

Information boards to educate visitors about the environment and how to help protect it 

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