Plate Tectonics

CE 1: TECTONIC PROCESSES (EVERYTHING YOU NEED TO KNOW!) Earth’s CRUST broken up into huge slabs of rock – TECTONIC All major EARTHQUAKES and VOLCANOES found at boundaries OCEANIC PLATES 5-10km thick heavier CONTINENTAL PLATES 25-90km thick lighter

Tectonic Plates move VERY slowly CONVECTION CURRENTS in Mantle drag plates along

Earth split up into 4 layers – CRUST, MANTLE, INNER CORE & OUTER CORE

CONSTRUCTIVE BOUNDARY ‘MID-ATLANTIC RIDGE’ (Atlantic Ocean) Plates diverge Mantle rock melts and erupts as lava New crust formed - sea floor grows Undersea ‘Vs’ form mid-ocean ridges Minor EQs as plates move

DESTRUCTIVE BOUNDARY PACIFIC RING OF FIRE Plates converge Crust forced into mantle (subduction) Oceanic crust melted/destroyed Explosive ‘Vs’ Powerful EQs as plates move

COLLISION BOUNDARY HIMALAYAS Plates converge Plates don’t sink into mantle Plates buckle = fold mountains Powerful EQs – no ‘Vs’

CONSERVATIVE BOUNDARY SAN ANDREAS FAULT Plates move in diff directions/speeds Plates become locked together Pressure builds-rock snaps at fault Plates move suddenly – powerful EQs

EQ magnitude (strength) measured using a SEISMOMETER against the RICHTER SCALE Richter Magnitudes <2.0 2.0-2.9 3.0-3.9 4.0-4.9 5.0-5.9 6.0-6.9 7.0-7.9 ≥8.0

Effects near Epicentre Generally not felt, but recorded Potentially noticeable Felt by some Felt by most Damaging shocks Destructive in populous regions Major earthquakes. Inflict serious damage Great earthquakes. Destroy communities near epicenter

Estimated Number per Year 600 000 300 000 49 000 6 200 800 266 18 1.4

PRIMARY EFFECTS of Earthquakes (immediately an EQ strikes) e.g. Buildings collapse, Things fall from buildings, Dams burst SECONDARY EFFECTS of Earthquakes (problems hours/days after an EQ) e.g. Fire breaks out, Disease, Water supply cut off, TSUNAMIs LONG-TERM EFFECTS of Earthquakes (problems years after an EQ) e.g. Unemployment, Homelessness, Economical & Emotional damage KOBE EQ (1995 – 7.2) Pacific Ring of Fire 1ry 200 000 buildings collapsed (5 500 dead) 2ry 230 000 homeless Other Approx 6months to recover from EQ NOW HAVE EQ-PROOF BUILDINGS

GUJARAT EQ (2001 – 7.9) Nr. Himalayan Plate Boundary 1ry 35million people affected, 1mill buildings collapse 2ry lots of disease, 10 000s fled area Other $1.3billion damage Quakes affected 1 016 villages & 8 urban areas

TECTONIC PLATES The Earth’s crust is broken into huge slabs of rock called tectonic plates. These vary in thickness:

Oceanic plates are 5km to 10km thick Continental plates are 25km to 90km thick

(denser) (lighter)

Oceanic plates are made from denser rock than continental plates. The diagram below shows the Global Distribution of the world’s main tectonic plates. Look at how the world’s major Earthquake zones and Volcanoes are found at the boundaries between plates.

PLATE MOVEMENT Tectonic plates move very slowly (approximately 2-3cm a year). 1. 2. 3.

The core remains hot due to radioactive processes. Heat from the core causes very slow movement in the mantle rocks called Convection currents. Movements in the mantle ‘drag’ the plates along.

See diagram below.

STRUCTURE OF THE EARTH The Earth is made up of four different layers: CRUST, MANTLE, INNER CORE, OUTER CORE. See diagram below.

At each part of the Earth’s structure different processes occur

PLATE BOUNDARIES Plate boundaries, or margins, are the places where two or more tectonic plates meet.

CONSTRUCTIVE BOUNDARY

e.g. ‘MID-ATLANTIC RIDGE’ (Atlantic Ocean)

DESTRUCTIVE BOUNDARY

e.g. ‘PACIFIC RING OF FIRE’ or 'WEST COAST OF SOUTH AMERICA.’

Oceanic plates diverge. Mantle rock melts and erupts as lava. New crust is formed and sea floor grows larger. Undersea volcanoes form mid-ocean ridges. Minor earthquakes occur as plates move.

Oceanic and continental plates converge. Denser oceanic crust is forced down into the mantle (subduction). Oceanic crust is melted and destroyed. Explosive volcanoes are formed. Powerful earthquakes occur as the plates move.

COLLISION BOUNDARY

e.g. HIMALAYAS (Asia)

CONSERVATIVE BOUNDARY

e.g. SAN ANDREAS FAULT (West Coast of N.America)

Continental plates converge. Plates are not dense enough to sink into the mantle. Plates buckle and form fold mountains. There are powerful earthquakes but no volcanic eruptions.

Tectonic plates move in different directions, or at different speeds. Plates become locked together. Pressure builds until rock snaps along a fault. Plates move suddenly, causing powerful earthquakes.

CAUSES OF EARTHQUAKES Earthquakes occur mainly on plate boundaries that are moving towards, or past, each other Over many years pressure builds up until eventually the rocks snap along a weak area called the FAULT LINE The place underground where the rock snaps is the FOCUS The place at the surface directly above the focus is called the EPICENTRE 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 THE HIGHER THE MAGNITUDE AND AMOUNT OF DAMAGE

EARTHQUAKE SCALES RICHTER SCALE Earthquake magnitude (the strength) is measured using a seismometer and these results are measured against the Richter Scale. The scale is logarithmic, each subsequent level is x10 more powerful than the previous. The scale is continuous (has no end) although nothing above 9.2 has not been recorded on land. Richter Magnitude 1 to 3.4 3.5 to 4.2 4.3 to 4.8 4.9 to 5.4 5.5 to 6.1 6.2 to 6.9

Description None, only recorded on seismographs Feels like the vibrations due to a passing lorry. Noticed by people at rest Noticed by everyone. Loose objects rocked, sleepers woken up and church bells ring. Trees sway, loose objects fall. Some damage. Walls crack, plaster falls. General alarm

Number Over 100 000 each year

About 100 each year

Over 8.1

Some buildings collapse. Chimneys fall. Pipes break. Ground fissured or cracked. Ground cracks badly. Buildings destroyed. Railways lines bent. Landslides. Only few buildings withstand shock, bridges destroyed. All pipes and cables broken, landslides, floods. Countryside devastated. Total destruction.

1 every 4 or 5 years

Richter Magnitudes <2.0 2.0-2.9 3.0-3.9 4.0-4.9 5.0-5.9 6.0-6.9 7.0-7.9 ≥8.0

Effects near Epicentre Generally not felt, but recorded Potentially noticeable Felt by some Felt by most Damaging shocks Destructive in populous regions Major earthquakes. Inflict serious damage Great earthquakes. Destroy communities near epicenter

Estimated Number per Year 600 000 300 000 49 000 6 200 800 266 18 1.4

7.0 to 7.3 7.4 to 8.1

14/15 each year

MERCALLI SCALE The effects of earthquake hazards can be also be measured on a scale. The Mercalli Scale measures damage caused. It is a descriptive scale ranging from 1 (rarely felt) to 12 (total devastation). No 1 2 3 4 5 6 7 8 9 10 11 12

Effects Detected only by instruments Slight vibrations, hardly noticed Slight vibrations, noticed by people not moving Moderate, felt by people moving about Quite strong, loose objects fall over Strong, slight damage to buildings Very strong, walls crack Destructive, chimneys fall Ruinous, buildings collapse Disastrous, many buildings destroyed Very disastrous, few buildings left standing Catastrophic, total destruction

EARTHQUAKES: 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 PLANNING and PREPARATION reduce the effects of a Tectonic Hazard 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 helps predict when hazards are coming so people can be warned

MONITORING 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 (SEE BELOW)

STRENGTHENED ROADS & RAILWAYS can help reduce damage (sometimes this doesn’t work – in Kobe 1995 – the Bullet Train track bent unexpectedly)

EFFECTS OF EARTHQUAKES These can be split into different types:

PRIMARY EFFECTS (Hazards which happen immediately an Earthquake strikes) 8 8 8 8

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

SECONDARY EFFECTS

(Problems faced in the hours and days after an Earthquake strikes) 8 8 8 8 8

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

LONG-TERM EFFECTS

(Problems that can continue for years after the Earthquake) 8 8 8 8

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

PEOPLE LIVING IN TECTONIC AREAS There are BENEFITS of living in areas which are prone to TECTONIC ACTIVITY 9

Volcanic LAVA and ASH make FERTILE SOILS so people settle and farm nearby

9

Precious MINERALS and FOSSIL FUELS are found in volcanic zones (like GOLD and DIAMONDS)

9

Land is CHEAP in volcanic and earthquake zones and people FEEL SAFER with technological advances like ‘EARTHQUAKE-PROOF’ houses

9

Many TOURISTS (bringing income) come to see features such as GEYSERS and bubbling MUD POOLS (people also believe that HOT SPRINGS created by Volcanoes improve health)

9

Some people are too POOR to leave their home (especially in LEDCs – also poor education) Even when people can afford to leave the area they may be ATTACHED TO THEIR HOME (not literally!)

*TRIVIA* RECENT SCIENTIFIC STUDIES HAVE REPORTED THAT SHED-LOADS OF PEOPLE ARE LIVING IN EARTHQUAKE ZONES - SO MANY THAT IT WOULD BE A NIGHTMARE TO RE-HOUSE THEM, AND MANY OF THEM DON’T WANT TO LEAVE ANYWAY

TECTONIC HAZARDS IN LEDCs & MEDCs EARTHQUAKES and VOLCANOES are a nightmare anywhere, but they cause MORE PROBLEMS FOR LEDCs THREE FACTORS 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 DENSITY

the more people the more deaths! e.g. Gujarat EQ 2001 – occurred in a 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** (like the one below!) 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 EMERGENCIES must be dealt with FIRST All casualties should be taken to hospital and 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

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 GET BACK 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.

COMMUNICATION is 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

5.

WATER and POWER supplies are normally POOR and mending them is difficult

6.

ROADS and TRANSPORT SYSTEMS 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

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 EFFECTS

Nearly 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

SECONDARY EFFECTS

Electricity, 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 An estimated 230 000 people were made homeless Industries, including Mitsibushi and Panasonic were forced to close

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 FINAL FIGURES FOR THE ‘KOBE EARTHQUAKE’ Death Toll 5500 Injured 40 000 Houses destroyed 180 000 The Kansai International Airport and Akashi Bridge were both undamaged – presumably due to their high-tech construction aimed at withstanding earthquakes

GUJARAT EARTHQUAKE The Gujarat Earthquake occurred in 2001 and measured 7.9 on the Richter Scale It happened at 8.46 (IST) on 26 January 2001, lasting 20 seconds The earthquake occurred in north-western India The epicentre was close to the small desert town of Bhuj in the north-western state of Gujarat 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 ach other pressure builds up. Eventually this pressure is released – this caused the earthquake in India

WHAT WERE THE EFFECTS OF THE EARTHQUAKE? PRIMARY EFFECTS

At least 21 000 people killed (a further 18 in Pakistan!) Initial figures suggested approx. 200 000 people injured 350 000 buildings destroyed and 750 000 damaged 400 school children and their teachers were covered by tons of falling masonry 35million people were affected in India More than 50 high-rise buildings collapsed close to the epicentre

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) 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 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 Death Toll Injured Homeless Cost

FOR THE ‘GUJARAT EARTHQUAKE’ 30 000 55 000 over 1 000 000 £2.2billion (estimated)