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Geography RevisionGeography Revision

Do we have to?

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The things to doThe things to do

Three topics onlyChanging Earth ( Earthquakes + oceans)Working world (economic activity + tourism)Fragile environments (Climate change, acid rain, energy sources, rubbish)PLUSMap questionKeyword section

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Changing earthChanging earth

The structure of the earth and earthquakes

Any question I ask will have the answers in the

‘notes’ section under the slide if you open to see

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The Structure of The Structure of the Earththe EarthA thin crust - 10-

100km thick and not very dense

A mantle – extends almost halfway to the centre, hot and dense

A core – made of molten nickel and iron. Outer part is liquid and inner part is solid. Gets hot due to radioactive decay. The crust is made up of pieces – what are they called?

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The convection currents in the The convection currents in the mantle force the plates to movemantle force the plates to move

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Now this is a strange looking Now this is a strange looking mapmap

What is happening and what is the name of the theory?

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Plate Margins Plate Margins For each one, explain what is happening, and why it has its name.The 4 examples we talked about were the Mid-Atlantic ridge, the Himalayas, the San Andreas Fault and the Andes.Which of these places go with each types of plate margins?

What can happen along any of these faults? (not pleasant!)

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Most earthquakes happen near the boundaries of tectonic plates, both where the plates spread apart and where they crunch or grind together But large temblors also strike from time to time in the normally stable interior of continents.

Movement of body waves away from the focusfocus of the

earthquake. The epicentreepicentre is the location on the surface

directly above the earthquake's focus.

So what happens when there is an So what happens when there is an earthquake?earthquake?

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How big it is, can be measured How big it is, can be measured ……

1 – 3.5: you would no be able to feel, even it was quite close by – but it would show up on a seismograph3.6 – 6: you would feel it, but it is unlikely to do much damage6.0 – 6.9: can be fairly destructive up to 100km7 -7.9: Major earthquake - can be very damaging – e.g. Haiti and New Zealand8 +:Great earthquake. Causes serious damage of 100s of km. Japan 8.9

.. using a seismograph.The amount it shakes is measured on the Richter scale

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There are 2 types of waves in There are 2 types of waves in an earthquakean earthquake

Body waves and surface waves. Body waves travel outward in all directions, including downward, from the quake's focus -- that is, the particular spot where the fault first began to rupture. Surface waves, by contrast, are confined to the upper few hundred miles of the crust.

They travel parallel to the surface, like ripples on the surface of a pond. They are also slower than body

waves.

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This what it would be like …This what it would be like …..the body waves (P-wave) strike first and are the fastest kind. People often report a sound like a train just before they feel a quake, which is the P-wave moving as an acoustic wave in the air. Then the secondary, or S-waves, arrive. A person in a building perceives the arrival of S-waves as a sudden powerful jolt, as if a giant has pounded his fist down on the roof. Finally, the surface waves strike. In very strong earthquakes, the up-and-down and back-and-forth motions caused by surface waves can make the ground appear to roll like the surface of the ocean, and can literally topple buildings over.

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What kind of damage can be What kind of damage can be done?done?

Look what the surface waves and body waves did!

The whole earth moved 5 metres in 1906 in San

Francisco

Mudslides

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What is this a picture of from What is this a picture of from Japan this year?Japan this year?

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So you are in an earthquake So you are in an earthquake zone – and you do not want to zone – and you do not want to

move away, so what can you do move away, so what can you do to stay safe?to stay safe?

1. Make sure the building you are in are well built, to withstand earthquakes as well as possible2. Have a personal plan

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The BuildingsThe BuildingsMovement is earthquakes is of 2 types, up-and-down and side-to-side. Most reasonable strong building can cope with the first. It is the 2nd that brings challenges!

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On a personal levelOn a personal levelDon’t leave bookcase just standing against the wall – screw them into it.Make sure cupboards have safety catches on them – even a small earthquake can make a big mess (or even a dangerous one, in the case of bleach or weed killer) if the bottles tumble out onto the floor and smash.Identify safe places indoors and out – places where glass will not fall on top of you for example – in doorways, under heavy tables etcPractice what do.Have an emergency contact plan.Have emergency supplies in a secure – if possible metal – container – e.g passports, birth certificates, money, batteries, torch etcDo check out http://www.fema.gov/plan/prevent/earthquake/preparedness_home.shtm#1

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What am I talking about?What am I talking about?Body wavesCollision plateConservative plateConstructive plateContinental driftConvection currentCoreCrustDestructive plate

EpicentreFocus MantlePlatesRichter scaleSeismographSurface wavesTsunami

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The coastThe coast

The processes that change the environment and what is

happening to the coasts

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There are 3 processes at There are 3 processes at work work

Erosion Transportation Deposition

I am using my hammer to

wear away this rock

I am carrying away the pieces

I cannot carry them any further so I

drop them

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Erosion is carried out in a number of Erosion is carried out in a number of waysways

ACTION

Can you work out what each word means?Attrition? Solution? Hydraulic action? Abrasion?

CORROSION

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I know this is river I know this is river transportation – but the seas transportation – but the seas

are the sameare the same

Here are the 4 ways in which the load – the material the waves are moving from one place to another – is transported.Learn these words and meanings

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DepositionDeposition

A waves drop their loadtheir load when the speed or volume of the waves decrease. The load, which it carries, is deposited. The heavier material is deposited first and the finer material carried further.

Deposition is likely to occur when:– waves enter an area of shallow water– waves enter a sheltered area– there is little wind

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What features can erosion What features can erosion make?make?

How easily a coast is eroded depends on how hard the rock isHeadlands and Bay!All the varieties of erosion figure here.Anyone want to have a go at explaining how one does it?Notice the darker patch in the bay in the last picture – what could that be?

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How cliffs are erodedHow cliffs are erodedThe tougher rocks of the headlands are gradually eroded away by all the methods of erosion and gradually a small ‘Wave-Wave-cut notchcut notch’ is made by the waves at high tideAs it gets bigger, the overhanging rock will eventually tumble into the sea.Over time the cliff retreats leaving a wave-cut wave-cut platformplatform just below the surface, that shows only when the tide is outThis is in Dorset near Purbeck at Kimmeridge Bay.

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This is an arch in limestone – which was the This is an arch in limestone – which was the main way in which it was eroded?main way in which it was eroded?

1. A large crack opened

up

2. The crack grows into a cave

3. The cave gets bigger

4. The cave breaks through the head land

to make an arch

5. The arch is eroded and collapses

3. This leaves a tall stack

3. This is eroded to

form a stump

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What happens next?What happens next?Once the rock has been eroded away from the cliff by abrasion and corrosion and hydraulic actionThe pieces will be further broken down by attrition, becoming smoother and smaller over timeSome of it will be transported away and deposited somewhere elseBroken rock ends up on beaches as sand or shingle (round pebbles)But beaches do not stay the sameMost of the waves break on the beaches at an angle.Some of the waves are constructive,constructive, which means they bring material from another place and leave it. These waves are swash wavesswash waves – quiet little waves that drop anything they are carrying as they breakThese make beaches bigger.

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Some of the waves are destructive,destructive, which means that they break on the beach and as the water runs back, it drags part of the beach away with it. These waves are backwash wavesbackwash waves – big waves that make more noise as they retreat, taking the sand and shingle with them.These make beaches smaller.

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Some waves are a bit of both. This is called longshore driftlongshore drift

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This can lead to the formation This can lead to the formation of a spitof a spit

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What with rising sea levels (climate What with rising sea levels (climate change) and coastal erosion, some change) and coastal erosion, some

coasts are disappearing fast.coasts are disappearing fast.So we have to have ways of trying control at least some of our coastlines if whole towns are not to disappear under the waves!There 2 groups of methods – hard engineering -These solutions generally involve concrete, metal, stone and other hard wearing materials that are intended to stop erosion and take little account of the environment.Soft EngineeringThese methods try not to disrupt the environment and tend to be used where the environment is more important than say a town or road.

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Are these hard or soft? Do you Are these hard or soft? Do you know what they are called?know what they are called?

What these for?

What do you think they have done

here? Why?

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Are these hard or soft? Do you Are these hard or soft? Do you know what they are called?know what they are called?

What is happening

here?

What is this for?

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There are others ..There are others ..

Revetments, GabionsRiprap

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What am I talking aboutWhat am I talking aboutErosionTransportationDepositionAttritionCorrosionHydraulic actionAbrasionSuspensionSolutionTractionSaltation

LoadHeadlandsWave cut notchWave cut platformArchStackStumpconstructive wavesSwash wavedestructive wave

Backwash waveLongshore driftSpitHard engineeringSoft engineeringReplenishmentRevetmentsGabionsRiprap