Introducing Volcanoes With a bit of revision first
Structure of the Earth • The Earth is made up of 3 main layers: • Core • Mantle • Crust Mantle Outer core Inner core Crust
Plate Tectonics • The Earth’s crust is divided into 12 major plates which are moved in various directions. • This plate motion causes them to collide, pull apart, or scrape against each other. • Each type of interaction causes a characteristic set of Earth structures or “tectonic” features. • The word, tectonic, refers to the *deformation of the crust as a consequence of plate interaction. • * deform = change shape
Plate Movement • “Plates” of crust are moved around by the underlying hot mantle convection cells
Three types of plate movements What happens at the margins of plates moving in this way?
Where do earthquakes form? Figure showing the tectonic setting of earthquakes
Earthquakes • Earthquakes occur mainly on plate boundaries that are moving towards, past or away from each other • Over many years pressure builds up until eventually the rocks snap along a weak area called the FAULT LINE • The point of origin of an earthquake is the FOCUS – this is the point where it starts from • The place at the surface directly above the focus is called the EPICENTRE What sort of margin is this?
The stored energy is released, travelling outwards in SEISMIC WAVES Seismic Waves are strongest at the epicentre of an earthquake – this is where the most damage is caused Seismic Waves spread out from the focus like ripples *AS SEISMIC WAVES TRAVEL OUTWARDS THEY LOSE ENERGY* The closer to the surface the focus of the earthquake is and the softer the rocks, the higher the magnitude of the seismic waves and the greater the damage
The magnitude of an earthquake is measured on the Richter Scale • An earthquake’s magnitude (the strength) is measured using a seismograph. • Each subsequent level is x10 more powerful than the previous on was. • The scale is continuous (has no end) although nothing above 9.2 has not been recorded on land.
PREDICTION & PREPARATION • PREDICTION • Earthquakes are very hard to predict • Scientists can search for clues: • changes in well water levels • gas emissions • cracks appearing in rocks • even strange animal behaviour!! • Computers can analyse data to forecast future earthquakes BUT they can’t be predicted accurately as they occur unexpectedly.
PREPARATION • Good panning and preparation can reduce the effects of tectonic hazards • EMERGENCY DRILLS are held to practise what to do in the event of an earthquake • INFORMATION on emergency procedures can be made available to the public (e.g. in school classes, pamphlets, newspapers), sheltering under a table or avoiding standing next to walls can save your life! • EMERGENCY PLANS can be drawn up by the local authorities and government and practised in order to reduce damage, death and injury • MONITORING helps predict when hazards are coming so people can be warned
PREPARATION • FAMILIES can organise supplies of food and water, dust masks, spare clothes, basic medical supplies, shelters, torches, batteries, mobile phones and other useful stuff • EMEGENCY SERVICES such as the Police, Fire Brigade and Ambulance service can be well prepared to deal with any hazard • EMERGENCY SUPPLIES of water and power can be organised in advance • BUILDING & ROAD DESIGNS can be planned for earth movements so they don’t collapse under the strain • e.g. New skyscrapers in earthquake zones can be built with a computer controlled counterweight, cross bracings and special foundations to reduce the impact of an earthquake
EFFECTS OF EARTHQUAKES • PRIMARY EFFECTS • (Hazards which happen immediately an Earthquake strikes) • Buildings collapse, killing and trapping people inside • Dams burst • Bridges and elevated roads collapse, crushing cars and people • Objects such as signs and glass fall from buildings, injuring people below
EFFECTS OF EARTHQUAKES • SECONDARY EFFECTS • (Problems faced in the hours and days after an Earthquake strikes) • Fire breaks out from broken pipes • Water supply is cut off due to broken water pipes • Disease spreads as there is lack of food and clean water • Access is difficult: buckled roads and railways, fallen telephone lines make travelling and communicating difficult • TSUNAMIs (Sea Waves of up to 30m, travelling at 500km/hour) may occur in coastal areas, where an earthquake has happened at sea
EFFECTS OF EARTHQUAKES • LONG-TERM EFFECTS • (Problems that can continue for years after the Earthquake) • Unemployment where offices and factories were destroyed • Homelessness while waiting for homes to be rebuilt • Economic damage as the government spends billions on rebuilding • Psychological and emotional damage to those involved
Earthquakes in LEDCs & MEDCs • Three factors that affect how serious the disaster is • Rural/Urban areas: rural areas have fewer people and buildings so the size of the disaster is smaller • Population size: the more people the more deaths! • e.g. Gujarat 2001 – very populated area = 20 000 deaths • How prepared a country is:this depends on how developed a country is • LEDCs have less time, money and expertise to prepare for hazards • MEDCs are better prepared but they still can’t stop disasters happening – they just limit the damage
MEDCs can put EMERGENCY PLANS into action • 1. Local authority experts assess the seriousness of the situation and the damage • 2. Local citizens are kept informed – they need to be reassured and told what to do next • 3. Immediate emergenciesmust be dealt with first • All casualties should be taken to hospital • Fires must be put out – these are a big problem if gas pipes have been damaged • 4. Disrupted public services such as power, water supply and sewage disposal must be restored as soon as possible because there is a risk of disease.
MEDCs can put EMERGENCY PLANS into action • 5. Communications such as roads, bridges, railways and telephones may have been damaged and mending these is a top priority so that HELP from outside the area can get in • 6. The efforts of individuals, government and NGOs (Non-Governmental Organisations) such as OXFAM must be coordinated • 7. Once the situation is clear, and there’s no risk of a further hazard – life can return to normal
LEDCs are NOT so well prepared • 1. Many people in LEDC hazard zones haven’t been given information about what to do if there is a hazard • 2. Some LEDCs DON’T prepare plans – the Government has enough problems already! • 3. Communications are bad – many people live in shanty towns with no proper access roads and badly built housing which collapses easily causing more injury.
Getting back to normal takes longer too • 1. There are few experts available to assess the situation • 2. Without plans there will be delays dealing with fires, injured people etc • 3. Badly built housing means more damage and allows fires and diseases to spread quickly • 4. Limited communications mean people still don’t know what’s happening – this means there will only be a few ambulances and fire engines available
Getting back to normal takes longer too • 5. Water and power supplies are normally poor and mending them is difficult • 6. Roads and transport are poor to start with, so it’s difficult to bring supplies of food, medicine, clothes, shelter – even if these are available! • 7. Lack of money means they have to rely on foreign aid which takes time to reach them • 8. Medical facilities are limited so many people die of injuries or disease linked to dirty water supply and poor living conditions
Gujarat Earthquake • The Gujarat Earthquake occurred in 2001 and measured 7.9 on the Richter Scale • It happened at 8.46 on 26 January 2001, lasting 20 seconds • The earthquake occurred in north-western India • The epicentre was 20 km NE of the city of Bhuj in the north-western state of Gujarat • It affected 16 million people
Gujarat Earthquake – why did it happen? • India lies on a collision margin. The Indo-Australian and the Eurasian Plate collide into each other at the rate of around 2cm per year • As neither plate can subduct (both plates are continental) the land where the two plates meet is forced upwards. • (This process has formed the Himalayas) • As the two continental plates move towards each other pressure builds up. Eventually this pressure is released – this caused the earthquake in India. • A major earthquake is expected about every 30 years, but it is impossible to predict when it will happen
WHAT WERE THE EFFECTS OF THE EARTHQUAKE? • PRIMARY EFFECTS • The ancient walled city of Bhuj was almost totally destroyed, as was nearby Anjar • At least 20 000 people killed (a further 18 in Pakistan!) • Initial figures suggested approx. 150 000 people injured • The high death toll was down to the poor construction of the buildings, • And also the fact that it was a holiday and most people were at home
WHAT WERE THE EFFECTS OF THE EARTHQUAKE? • PRIMARY EFFECTS • 350 000 buildings destroyed and 750 000 damaged • 400 school children and their teachers were covered by tons of falling masonry • 16 million people were affected in India • More than 50 high-rise buildings collapsed close to the epicentre.
WHAT WERE THE EFFECTS OF THE EARTHQUAKE? • SECONDARY EFFECTS • An estimated 1 000 000 people were made homeless and in need of immediate relief including water, food, shelter and protection from disease • After the initial Earthquake 1000s slept in the open air (for fear of being caught in collapsing buildings) – danger of exposure • Quake victims were all vulnerable to diseases (typhoid, cholera and gastroenteritis)
WHAT WERE THE EFFECTS OF THE EARTHQUAKE? • SECONDARY EFFECTS • Many hospitals were destroyed – patients treated in the open air (desperate need for beds and medical supplies for the wounded) • Gas pipelines, power supply stations, phone lines and water services were SEVERELY affected • 10s of 1000s of people fled Gujarat as aftershocks continued • Approx 350 aftershocks, the largest measuring 6.0
What help was available? • Short term • Indians troops, from neighbouring Pakistan and from across the world came to help • But due to the damage to the transport system, power and communication, this made finding who needed help and getting it to them very difficult. • Many people were trapped in rubble as there was no machinery to help dig them out.
What help was available? • Long term • The Indian government received help from the World Bank ($500 million) and the Asian development bank($150 million). • Quake proof housing was introduced. • But because of the extra cost and need for more homes very quickly, some builders did not comply with the new standards and government did not force them. .
WHAT HAPPENED IN THE MONTHS AFTER THE EARTHQUAKE? • Extensive infrastructure and material damage – estimates at $1.3billion • Quakes affected 1 016 villages and 8 major built-up areas • FINAL FIGURES FOR THE ‘GUJARAT EARTHQUAKE’ • Death Toll 20 000 • Injured 150 000 • Homeless over 1 000 000 • Cost £2.2billion (estimated)
KOBE EARTHQUAKE • The Kobe Earthquake occurred in 1995 and measured 7.2 on the Richter Scale • It happened at 5.46am on 17 January 1995, lasting 20 seconds • During this time the ground moved 18cm horizontally and 12cm vertically • The Earthquake occurred because Japan is at the centre of Destructive Plate Boundaries
WHAT WERE THE EFFECTS OF THE EARTHQUAKE? • PRIMARY EFFECTSNearly 200 000 buildings collapsed 1km of the elevated Hanshin Expressway and numerous bridges collapsed 130km of the ‘Bullet Train’ route was destroyed • Several trains on minor lines were derailed 120 of 150 quays in the port of Kobe were destroyed
WHAT WERE THE EFFECTS OF THE EARTHQUAKE? • SECONDARY EFFECTSElectricity, gas and water supplies were disrupted. • Roads were at gridlock, delaying ambulances and fire-engines. • Fires, caused by broken gas pipes and ruptured electricity mains, raged for several days destroying a further 7500 houses and killing another 500 people. • An estimated 300 000 people were made homeless. • Industries, including Mitsibushi and Panasonic were forced to close.
WHAT WERE THE EFFECTS OF THE EARTHQUAKE? • WHAT HAPPENED IN THE MONTHS AFTER THE EARTHQUAKE? • Kobe’s infrastructure, including water, electricity, gas and telephone services were not fully operational until July • All rail services were back to normal by August • Most commercial buildings were rebuilt • One year later the port of Kobe was 80% operational • Replacement buildings had to meet stronger earthquake-resistance standards • There was an increase in the number of seismic instruments to record earth movements in the region
WHAT WERE THE EFFECTS OF THE EARTHQUAKE? • FINAL FIGURES FOR THE ‘KOBE EARTHQUAKE’ • Death Toll 6400 • Injured 40 000 • Building destroyed 100 000 • Homeless 180 000 • Estimated cost $200 billion • The Kansai International Airport and Akashi Bridge were both undamaged – presumably due to their high-tech construction aimed at withstanding earthquakes
Homework • Read through slides 12 to 23 to remind yourselves what are the causes and effects of an earthquake, and what can be done to minimise these effects. [Also in the textbook p39-41]. Then look at both case studies and answer this question: • Compare and contrast the effects of earthquakes on LEDCs with MEDCs. • This does not mention using the case studies but woolly, unsubstantiated statements do not get the marks! So this is what is needed: e.g. • Although both earthquakes happened in densely populated areas, more people were made homeless in Bhuj, India than in Kobe, Japan (1 million against 100,000) • [Try for at least another 3 ideas]