Plate TectonicsThe structure of the earth

The earth structure is split up into four layers, these are the crust , mantle, outer core and inner core.

The crust: The crust covers the mantle and is the earth's hard outer shell, the surface on which we are living. Compared to the other layers the crust is much thinner. It floats upon the softer, denser mantle. The crust is made up of solid material but this material is not the same everywhere, this layer has the least dense and coolest. There are two types of crust, the oceanic and continental, these have a range of thickness with up to 70 kilometres on the continental crust and only 10 kilometres on the oceanic crust. It is separated from the Mantle by the Mohorovijic (Moho) boundary.

The mantle: The layer above the core is the mantle. It begins about 6 miles (10 kilometres) below the oceanic crust and roughly 19 miles (30 km) below the continental crust. The function of the mantle is to separate the inner mantle and the outer mantle. It is about 1,800 miles (2,900 kilometres) thick and makes up nearly 80 percent of the Earth's total volume. It is a semi-moltern layer at about 5000°c, at these high temperature there are convection currents in the mantle.

The outer core: The outer core is about 1,800 miles below the earth's surface and is roughly the size of Mars. The core is a dense ball of the elements iron and nickel which are liquid at about 6000°c.The inner core: This is also at 6000°c but due to the high pressure the nickel and iron which it is made up of remains solid it is at the centre of the earth.

Lithosphere:This is the layer of the earth which consists the ridged top part of the Mantle and the crust layers.

Asthenosphere:The asthenosphere is the ductile part of the earth just below the lithosphere, including the lower mantle. The asthenosphere is about 180 km thick.

Both parts are in a series of interlocked pieces called plates The point between 2 plates is called a plate boundary The plates are constantly moving (very slowly). In parts of the world where the plates are

moving apart, a constructive (or divergent or tensional) plate boundary is formed. New oceanic crust is formed as the magma rises and solidifies e.g. Eurasian and North American Plates.

In other parts of the world the plates are moving together e.g. the Nazca and South American plates creating destructive (convergent or compressional) plate boundaries , where crust is being destroyed.

Finally in areas of the world where the plates are sliding past each other, sometimes in the same direction e.g. the Eurasian and South American plate or in opposite directions e.g. the Pacific and the Juan de Fuca Plate. There are called conservative (transverse or passive) plate boundaries.

Plate boundaries are associated with tectonic activity but the type of tectonic activity is largely determined on the type of plate boundary.

Why Plates Move

Plates at our planet’s surface move because of the intense heat in the Earth’s core that causes molten rock in the mantle layer to move. It moves in a pattern called a convection cell that forms when warm material rises, cools, and eventually sink down. As the cooled material sinks down, it is warmed and rises again.

Scientists once thought that Earth’s plates just surfed on top of the mantle’s giant convection cells, but now scientists believe that plates help themselves move instead of just surfing along. Just like convection cells, plates have warmer, thinner parts that are more likely to rise, and colder, denser parts that are more likely to sink.

New parts of a plate rise because they are warm and the plate is thin. As hot magma rises to the surface at spreading ridges and forms new crust, the new crust pushes the rest of a plate out of its way. This is called ridge push.

Old parts of a plate are likely to sink down into the mantle at subduction zones because they are colder and thicker than the warm mantle material underneath them. This is called slab pull.

Proof of plate movement/continental drift

Alfred Wegener predicted in the 1930s that the world was once one supercontinent called Pangaea. He said that 200 million years ago it had begun to break up and formed two continents called Laurasia and Gondwanaland 150 million years ago. Thereafter 100 million years ago the continents began to split and 50 million years ago they had started to spread out into the world map we know today.

Evidence to support this includes:

Fossil evidence - same species of land animals found on opposite sides of the Atlantic Ocean Climate evidence - coal deposits and fern fossils in Antarctica (showing it used to be more

equatorial). Also glacial deposits in India, South America, Africa and Australia which are too hot for glaciers today.

Similar rock types - same age and composition found in Africa and South American continents

Continental fit- Some continents such as the eastern seaboard of South America and western seaboard of Africa seem to fit together like a jigsaw puzzle.

Paleomagnetism- The evidence for plate tectonics is the alternating polarity of the rocks that form the ocean crust. Iron particles in lava erupted on the ocean floor are aligned with the Earth’s magnetic field. As the lavas solidify, the iron they solidify and provide a permanent record of the Earth’s polarity at the time of the eruption - called paleomagnetism. This happens as the earth’s polarity flips roughly 400000 years since the iron line up when it is created with the magnetic north, the striped pattern, which is mirrored exactly on either side of a mid-oceanic ridge, suggests that the ocean crust is slowly spreading away from this boundary.

Constructive Plate BoundariesThere are two types of constructive plate boundary.

Oceanic-Oceanic - e.g. North Atlantic Ridge Continental-Continental - e.g. African Rift Valley

Oceanic-Oceanic Boundaries

Here rising convection currents force two plates apart, the release of pressure on the asthenosphere causes it to become molten and rise.

Process: Sea Floor Spreading

Rising magma forms new oceanic crust along the oceanic ridges and old crust is being destroyed at oceanic trenches. The concept of sea floor spreading and continental drift were combined to create the theory of plate tectonics.

Evidence for this includes that there is an oceanic ridge system e.g. the Mid-Atlantic Ridge in all of the world’s oceans. Also the youngest rocks in oceans are found along the ocean ridge system and the oldest rocks are present along the margins of ocean basins.

Volcanic Activity

Shield Volcanoes

Dominated by fluid, high temperature, low viscosity, basaltic magma Low, dome shaped profile Typical slopes of 15° Lava flows down slope, away from the central vent Many shield volcanoes have a central caldera Examples: Hekla and Katla

Ocean Ridge Volcanoes

Volcanic activity under water, for example at the Mid Atlantic Ridge Submarine oceanic ridge volcanoes e.g. Surtsey 1964, form new islands Passive volcanic activity, low magnitude and not dangerous

Volcanic activity at conservative plate margins is often associated with fissure type eruptions.

Why is volcanic activity at constructive plate margins non-violent?

Composition of the magma determines the type of rock that forms and its behaviour during the eruption

Chemical composition (SiO2 content) and the gas content (H2O and CO2) are the main behaviour controls

SiO2 content controls the viscosity of magma

Viscosity: a measure of how easily a fluid flows. Water has a low viscosity and molasses have a far higher viscosity

Viscosity in turn controls the amount of gas that can be trapped in the magma. The greater the viscosity, the more gas in the magma.

Types of magma:

Basaltic Magma: constructive boundaries - low viscosity, slow cooling, low gas content - shield volcanoes - gentle eruptions

Type of magma leads to the violence of eruptions, high SiO2 magmas with high gas content tend to plug vents leading to explosive eruptions.

There is no seismic activity at constructive plate margins

Continental-Continental Plate Boundaries

Process: Rifting (Block Faulting)

When a block of land slips down as the land on either side has moved away to form a Rift Valley e.g. the East African Rift Valley

The floors f rift valleys often have volcanoes along the floor e.g. Mt. Kilimanjaro which is dormant. They form as the plates pull apart and the magma rises to the surface.

Destructive Plate BoundariesThese types of boundaries are:

Continental-Continental Boundaries Oceanic-Oceanic Boundaries Oceanic-Continental Boundaries

Continental-continental Boundaries

When two continents meet in a collision zone, there is very little/no subduction (no volcanic activity as neither are absorbed into the mantle) as both are relatively light and buoyant, resisting downward movement. The outcome is that two continental masses become crumpled and compressed together to form Fold Mountains e.g. The Himalayas.

Geosynclines: This is a vast down warping of the crust which occurs when two continental plates collide. This is the start of Fold Mountains. A sea will occupy the geosynclines and over millions of years sedimentary rocks will form in the base. The ongoing collision of the 2 plates will fold these sediments into antisyncinoriums and synclinoriums i.e. a mountain range.

The types of Lava

Andesitic Magma: destructive boundaries - high viscosity, fast to solidify, high gas content -composite volcanoes - explosive eruptions - full of impurities from subduction of plate

Rhyolitic Magma: destructive boundaries - high viscosity, fast to solidify, high gas content -composite volcanoes - explosive eruptions - full of impurities from subduction of plate

o

Oceanic-Oceanic Convergence

Here the is subduction of the lithosphere which leads to volcanic activity as the material melts and forms magma

As the plate is subducted there is a lot of friction leading to submarine earthquakes which in turn can cause tsunamis. As the two heavy oceanic plates converge, the sinking plate exerts a strong dragging force creating a pronounced trench, e.g. the Marianas Trench that cuts 11000m into the earth’s crust

Oceanic-oceanic boundaries have a lot of frictional heat which gives high rise to abundant molten magma arriving at the earth’s surface to create a string of volcanos following the curved line of the trench. This string of volcanic islands is called a island arc. E.g. the Japanese Ryukyu Islands and the Hawaiian islands

Tsunamis

These are caused as a result of natural primary hazards meaning they are a secondary hazard mostly as a result of tectonic activity

The water is vertically displaced and waves move outwards

as the sea floor is deformed as the earthquake strikes. Tsunami waves travel very fast on the open ocean but their

destructive power comes from their towering heights which they attain as they approach the coast

Waves travel at 800km/h (500mph), but due to enormous wavelength the wave oscillation can take 20-30mins to complete a cycle and has amplitude of 1metre.

Very difficult to detect over deep water meaning they go unnoticed by ships

Management of Tsunamis

Prediction:

Pacific Ocean Tsunami Warning System - gives an early warning - however there is no such thing in the Indian ocean (poor suffer more)

Communication in MEDCs e.g. telecommunications better than in LEDCs which prevents prediction reaching the poor in LEDCs

Education:

Local population aware of hazards in MEDCs and are taught how to respond Nothing like this in LEDCs

Protection:

Buildings along a coastline have preventative measures taken to lessen tsunami impact

Building walls are built perpendicular to the shore, so waves can go through them rather than knocking them over.

Stilts used to prevent damage Forest planting between the coastline and buildings as trees rapidly slow waves down and

cause them to lose a lot of energy

Continental-Oceanic Convergence

Where oceanic and continental plates meet, the heavier oceanic matter sinks below the lighter continental plate in the subduction zone.

One example is the Nasca plate being subducted beneath the South American Plate. Subduction zones are commonly marked by a long narrow trench in the ocean floor.

Strong destructive earthquakes are associated with this type of plate margin and may occur on the surface or as deep as 700km

Volcanic activity is also a feature of subduction as molten material from the subducted plate works its way back through the continental plate under considerable pressure to create violently erupting composite volcanoes.

New fold mountains creation but with a volcanic root e.g. Mount St. Helens Tsunamis, generated close to the shoreline can also occur at this type of plate margin

Volcanic Activity

Volcanoes result from magma rising of the melting subducted plate The composition of the magma is andesitic (melted basaltic crust plus sediment carried on

the crust) The magma is very gaseous, particularly when enriched with water vapour - high explosive

eruptions Stratovolcanoes are constructed from feeder conduits extending to the surface Granitic (rhyolitic) intrusions are also formed, becoming trapped within the volcanic pile

overlying the region of subduction giving potential for very explosive eruptions

Stratovolcano/ composite volcanoes

These are volcanoes which alternate between periods of lava flows (constructive phase) and periods of explosive eruptions (destructive phase).

Called ‘composite volcanoes’ as made up of both lava flows and pyroclastic deposits, they can lay dormant for hundreds of years e.g. Vesuvius

Andesitic magma is a mix of basaltic and rhyolitic magmas in many cases. Gases add great pressure when the feeder conduit becomes plugged, contributing to the explosive power.

Stratovolcanoes can grow 1000s of metres high during the constructive lava phase

Constructive phase often ends with a destructive phase - an explosive eruption

Seismic Activity

This occurs at a very high magnitude as heavier oceanic plate is subducted under continental plate releasing large amounts of energy and causing a high magnitude earthquake.

Transform Boundaries Here the dominant form of movement is sideways, with the plates slipping past each other.

These are also known as passive or conservative plate boundaries The San Andreas Fault is an example of this where the Juan de Fuca plate is moving against

the North American Plate. Sections of the fault creep forward building pressure, then locked segments slip past each other causing earthquakes

No subduction so no volcanic activity at transform boundaries

Case Study: Haiti 2010

Date: 12th January 2010 Magnitude: 7 Depth: 13km 316000 deaths 300000 injured 1 000 000 homeless caused major damage to capital Port-au-Prince No building regulations so everything destroyed Starvation and diseases were secondary impacts Damage to communication systems, hospitals, transport and electrical networks hindered

aid and response

HotspotsThis is a point on the crust immediately above a hot plume within the mantle

Heat from the mantle (and some magma) rises to the hotspot (basaltic magma)

The rising mantle material is called a mantle plume.

Very passive eruptions from shield volcanoes due to the magma’s composition

Case Study: Hawaii

Long chain of 129 volcanoes, of which 123 are now extinct as the plate moves north-west

As the plate continues to move there will be a new Hawaii and islands further up the chain will die to form submarine seamounts.

Extrusive volcanic Features

Geysers: water is heated at depth in the crust by magma changes. This can occur in areas where active volcanoes do not exist. The superheated water can escape periodically as steam and hot water. A geyser is an intermittent turbulent discharge of superheated water ejected and accompanied by a vapour phase. When hot water moving upwards mixes with muds near the surface, a bubbling, boiling mud volcano may form. In some places e.g. in Pamukkale, Turkey they have become tourist attractions.

Fumaroles: areas where superheated water turns to steam as it condenses on the surface. This and geysers are typical of Solfatara areas in Italy where the escaped steam and water are mixed with sulphur rich gases.

Solfatara: This is where gasses mainly sulphurous it is released on to the surface.

Intrusive volcanic Features

Form as magma cools and solidifies within the crust, particularly along faults and bedding plains.

Battholith: e.g. Dartmoor, Devon - massive magma intrusions into the crust which cools and solidifies. Tors are the uppermost part of the exposed battholith.

Dyke: magma intrusion into a vertical fault which solidifies. Not usually visible as are small scale intrusive features. Sometimes a swarm of dykes will form.

Sill: e.g. Great Whin Sill, Northumberland - cooled and solidified magma between two strata (layers of rock) along the bedding plain. These are not usually visible but can be seen at the high force waterfall on the northern part of the River Tees.

Lacolith: when magma cools and solidifies along the bedding plain but the volume of magma forces the overlying strata into a dome which will become visible at the surface as a small hill. Cedar Tree Lacoliths can form which are multiple intrusions along the bedding plains.

Process: Seismic Activity

High magnitude seismic activity, but low volcanic activity An earthquake is ‘a vibration of the earth’s surface caused when energy is suddenly released

through the dislocation of segments of the earth’s crust’. At destructive plate boundaries the crust is subjected to strong bending forces and will

suddenly break and move to a new position when its strength is exceeded. This sudden movement generates shock, or seismic waves which travel outward from the point where the energy was released, known as the focus.

Most damage will occur at the epicentre, the point on the earth’s surface immediately above the focus.

P and S Waves

P waves: primary waves: these are longitudinal waves which push and pull the earth. They are the fastest body wave with speeds of 6km/s meaning they arrive first

S waves: secondary waves: these are transverse waves which shake the earth from side to side. They arrive second at speeds of 4km/s.

S waves will only travel through solids P waves travel through solid and liquid and are refracted as they pass

through a medium The paths of the waves are curved as they density is gradually changing

Magnitude

The Richter Scale

Earthquake strength or magnitude is measured on the Richter Scale. This scale is logarithmic meaning that each point represents a ten-fold increase in the amount of energy involved

Earthquake magnitude is measured using a seismometer or seismograph on a scale of 1-8.

The Mercalli Scale

This measure the intensity i.e. the damage caused rather than the energy This is a scale of 1-12.

Management of Natural Hazards

Assessing Hazards and Risks

Hazard and risk assessment are not synonymous

Hazard Assessment consists of the following:

When and where hazardous processes have occurred in the past and the severity of the physical effects of the past hazardous processes (magnitude)

The frequency of occurrence of hazardous processes The likely effects of a process of a given magnitude if it were to occur now Making all of this information available in a form useful to planners and public officials

responsible for making decisions in the event of a disaster

Risk Assessment involves not only hazards from a scientific point of view but also the socio-economic impacts. Risk is a statement of probability that an event will cause a certain amount of damage or a statement of economic damage of an event. It consists of:

Hazard assessment as above Looking at the location of buildings and other infrastructure in the areas subject to hazards Potential exposure to the physical effects of a hazardous situation The vulnerability of the community when subjected to the physical effects of the event

This aids decision makers and scientists to compare and evaluate potential hazards and set priorities on mitigation and on where to focus resources and further study

Hazard Prediction - involves when, where and how big

Some hazards such as tropical cyclones are highly predictable in terms of where and when they will strike. Their likely impact is also often correctly judged

Some hazards, such as volcanic eruptions are predictable to a degree. It cannot be precisely said when they will next erupt, but precursors give some short term warning. The nature of the volcano also gives an indication of what type of eruption to expect.

Other hazards, such as earthquakes and landslides are totally unpredictable as it cannot be said when, where of how damaging they will be.

Earthquake Prediction

Earthquakes in terms of their precise location, time of occurrence and magnitude cannot be predicted

There have been many failed and yet to be successful attempts at earthquake prediction and these include:

o Animal behaviouro Mapping epicentres of pre-quakes o Radon gas levelso Changes in water levels in wells

Mapping the location of miniscule earthquakes showed no correlation so cannot be used to predict large earthquakes

The seismic gap theory was tested at Parkfield California and looked at the historical records, finding that every 20-30 years there was a magnitude 6 quake. However a small earthquake predicted a large earthquake in 3 days however this never came so the theory failed. This uses the patterns of earthquakes which have occurred in the past.

Radon gas levels were thought to move to different levels which could then be measured to predict quakes however this was also ineffective.

Changes in water levels were supposed to help show cracks in the surface which would indicate an earthquake

Animal behaviour - it was said that snakes and rats appeared drunk just before an earthquake

Volcano Prediction

Volcanoes can be continuously monitored by taking accurate measurements, however many surveillance methods are very expensive and require skilled operators and sophisticated instruments in observatories. The problem is that many of the most dangerous volcanoes are situated in developing countries which do not have the money for careful observation of their volcanoes.

There are number of different methods which are often used in conjunction with one another.

Seismographic Monitoring - Rising magma causes earth tremors which will increase in frequency and intensity as it approaches the surface. These shallow volcanic earthquakes

are the most reliable sign that a volcano is going to erupt. They can be detected by automatic telemeter recorders which relay immediate interpretations to an observatory. Hawaii for example has 51 seismometers.

Tiltmeters - there are accurate levels composed of three graduated pots arranged in a triangle and filled with water or mercury. Rising magma often causes ground deformation which is recorded by the tiltmeters. Tilting is recorded when rising magma causes a bulge which happens slowly as an eruption looms. For example the Mount St. Helens Bulge could be seen for 2 months before the eruption.

Surveillance by Satellite - this is a very costly method that is still relatively new. However it offers some of the best future prospects for volcano prediction. The Global Positioning System (GPS) is used to monitor ground displacements which could pinpoint future activity. GPS uses data transmitted by orbiting satellites. For example the TOMS satellite produced an image of the Pinatubo volcanic cloud emitted during the 1991 eruption.

Gas and Steam Emission - increased emissions from fumaroles, mudpots and solfatoras can indicate that magma is rising closer to the surface. However such information is difficult to collect because the emissions can damage the instruments. For example greater fumaroles activity gave warning of the Askja eruption in 1961. However there has been increased fumarole activity near Mount Baker in 1975 but an eruption has never materialised.

Hazard Assessment Maps - On these the areas of greatest danger and highest risk around the volcano are identified. This means that danger zones can be precisely pointed out correctly so that people living in the danger zones can be evacuated. This is very effective for example with the 1980 Mt. St. Helens eruption where 35000 were evacuated.

Hazard Protection

There are a variety of methods which can be used to protect against both earthquakes and volcanoes.

Earthquake Protection - saves lives but no earthquake proof

Education - teaching people what to do when an earthquake strikes, before, during and after

Building regulations - use high quality materials and improved strict regulations to protect against damage

Diagonal bracing - used in buildings in addition to reinforced concrete Wooden buildings - wood is more flexible so is less likely to collapse during an

earthquake Cut electric supply when >5.0 quakes strike - prevents secondary hazards such as fires Hazard Mapping - looks at the configuration of faults, soils and buildings etc to know

where buildings should not be built - GIS systems Improvement in telecommunications - helps facilitate rapid response Vertical columns - these are extremely strong and prevent buildings from pancaking Lead extrusion dampners - with these the ground will move but the building will not,

preventing the building from collapsing e.g. under the Claston Building Metal jackets on reinforced pillars -prevents concrete from falling out and causing the

concrete to collapse as it did for example on the Shanghan Highway.

Soft Soils - Resonance and Liquefaction

These go against all earthquake protection, no matter how well the building is built it will collapse if built on soft soils.

Liquefaction - soft soils turn to quicksand when an earthquake strike so buildings will fall over

Resonance - buildings that are between 3-6 storeys high will resonate and destroy themselves - they will shake themselves until they collapse

Case Study : New Zealand

B values used to try and predict quakes however b value was supposed to be high just before a quake although there has been high b-values for a long time and no earthquake.

1931 Napin Quake was the turning point in protection in New Zealand Decided to begin building with wood rather than stone making N.Z homes some of

the safest in the world Car ports were banned and existing buildings reinforced Earthquake building code was imposed in 1935 and is the strictest in the world

Volcanic Eruption Protection

Structural (Mainly MEDCs)

Concrete shelters to protect from volcanic bombs e.g. Mt Unzen in Japan Concrete lava/lahar diversion channels - Mt Unzen, Japan Pitched roofs made from corrugated iron - Iceland Building houses on stilts to protect against lahars

Non-structural (behaviour modification - most effective in MEDCs

Drills, education and simulations with the civil defence Issue hard hats and face masks Evacuation e.g. Mt St Helens, Montserrat Establishing danger zones to prevent public access Regular news updates on the state of volcanic activity

ResponseImmediate

This is the life sustaining response:

Shelter - tent etc can come from charities, government etc - emergency aid Access to clean water - mainly through Non-governmental organisations (NGOs) Food - NGOs and foreign governments First aid (medicines) - MSC, Red Cross, NGOs Airlifts usually organised - helicopters and Chinooks by foreign governments

Pontoons (temporary bridges) built to help initially repair roads to help aid - usually involves foreign military

Bulldozers sent to clear landslides, debris etc International recue - very fast response that rescues survivors with heat sensing, dogs and

infrared - sent by MEDCs Evacuation of people from the area Money - however much is often lost/misapprotionated

Medium Term

Electricity, water, sewage supplies restored to prevent the spread of disease - however sometimes none of these things are in place originally

Construction of poor permanent bridges/roads Restoration of telephone masts - helps aid workers communicate

Long Term

Rebuilding of homes, schools, hospitals etc - however requires money e.g. donations from world bank or directly from MEDCs - unilateral/multicultural aid.

Multicultural aid - aid for one country from many but often with strings/conditions attached

Development aid - this is the best type of aid as no conditions. Usually comes from NGOs e.g. to establish stable farming - this is needed of a country is ever going to develop/improve.

Disaster Management

Prediction/protection - however most structural protection beyond the means of most LEDCs

There is no way LEDCs will ever have the technology to predict disasters without receiving aid

Hazard mapping will only be effective if the economic benefits of living in dangerous areas e.g. on the slopes of active volcanoes are outweighed by the potential dangers

Case studies

Mount Pinatubo

Where: Philippines, East Asia

Plate boundary: Philippine plate sub-ducts beneath the Eurasian plate

When: 1991, 7th to 15th June

Type of volcano: Composite or stratovolcano due to Andesite lava present.

Last eruption: 1380

VEI: 6

Timeline:

April 2 nd : Volcano started having small eruptions along a 1.5 km fissure, these continued for a couple months with the surrounding areas being dusted with volcanic ash and there being hundreds of small earthquakes every day. First evacuation of 5000 people happened

May 13 th -28 th : Rapid increase in the amount of Sulphur Dioxide so there is rising magma in the volcano, by the 28th May this has decreased a lot which would mean that the magma had been blocked.

June 5 th : The First eruptions with magma happened, there was also a high alert sent out that there could be a major eruption within the next two weeks.

June 7 th : There had been a large lava dome form which caused a evacuation area of 20km from the volcano and 20,000 people evacuated

June 15 th : The big eruption lasted for nine hours, which caused a ash plume which was 7km high. A tropical storm called Yunkya caused the ash to mix with the water vapour which caused lahars down river valleys. There was a 10 up to 30 inches of ash covering a 2,000km radius from the mountain.

After June 15 th : A large amount of sulphur dioxide to be released (15 – 30 million tons), this mixed with water and oxygen to become sulphuric acid to fall as rain which is harmful to people. The gas and ash reached 34km into the atmosphere which was then transported around the world

Effects :

Short term

Jets flying over the Philippines sustained damage and cost about $100,000 in repairs About 20 million tons of sulphur dioxide were released into the atmosphere Over 800 people were killed The volcano itself was decrease in height by 2.5 km 58,000 in total evacuated $700 million in total damages 4,000 homes were destroyed and 70,000 were damaged

Roads were damaged

Long term

There were 200,000 people effected in the area. The local American air base was shut down Global temperatures dropped by 1° around the world for a year Over 1 million animals died Respiratory disease

Management

Some 58,000 people were evacuated Massive rebuild effort was put into place to help the local communities recover from

the disaster Thanks to early warning system there were 5,000 people saved and a $250 million in

property damage

Response

Clarks air base which was locate near the volcano was abandoned by the US forces The government improved the strategies for long term aid and disease control also

evacuations were more prepared for. Improved alert systems for better early warning with a more integrated system so

more people can knows there’s a evacuation in place. They had also increased the amount of storage of medical supplies food and water in

preparation for disaster. Some people moved away from the area

Mount St. Helens

Where: North America, In the state of Washington

When: March 20th- May 18th 1980

What plate boundaries: Subduction zone Juan de fucia plate subducts beneath the North American plate

Last Eruption: 1857

VEI: 5

What caused it: From March 20th earthquakes of magnitude greater than 4.0 on the richer scale was directly beneath the volcano occurred

There were minor earthquakes at 15 per hour after that, and then from 27 th March there were earthquakes greater than 4.0 on the richer scale occurring at least 3 times a day. This then increased to about 8 per day just before May 18th

Then in the last week of April until May 18th there was a growth of a bulge on the north face of the volcano this was called a cryptodome this was due to a blockage in the main vent.

Then on May 18th at about 8;42 am local time a 5.1 earthquake hit directly beneath the volcano caused the north face of the volcano to become a landslide this cause the magma which was under pressure to suddenly erupt which cause a Pyroclastic flow and ash column to grow to a height of 12 miles which was called a Plinian eruption,

Main eruption:

The landslide on May 18th covered an area of 23 miles which had a speed of 240km/h. There was a lateral blast due to plug being removed, which reached 17miles north of the

volcano which had temperature of up to 350°c Lahars came from the Columbia and the Cowlitz River which affected up to 300km of the

river Pyroclastic flow covered an area of 6 miles and reached 5 miles from the volcano which was

about 700°c at speeds of up to 130 km/h Ash reached a height of 12 miles and fell in 11 states as far as 430 km away and had a depth

of up to 10 inches from the volcano

Short term impacts

57 people died Mud flows covered some areas by 50m Ash covers an area of 22,000 miles2

Ash reached east coast of America 47 bridges, 185 miles of highway and 15 miles of railways all destroyed 200 house destroyed Ash created problems with water treatment and transport systems Estimated cost of $2.74 billion Volcano decreased in height of by 400m Over 50,000 animals died with over 40,000 salmon lost due to forced to swim through

turbines in hydroelectric dams along the rivers.

Long term impacts

Due to crop loss it cost 100 million which is 7% of crop value for that region Tourism vastly increased after the eruption due to interest in the volcano Very expensive cleanup of the area affected Power blackouts due to falling ash

Management

There was as of April 30th a red zone around the volcano which people was restricted access and forced to pay a fine of $500 or imprisonment for 6 months.

After government appointed $1 billion was supplemented to help disaster relief.

Response

Lots of ash had to be removed with an estimated weight of 1 million tonnes and cost $2.2 million to remove and some places even took 10 weeks to be cleared

Lots of timber had to be cleared so many people gained jobs if only temporary $1 billion was supplemented to help disaster relief

Earthquake case-study

Haiti

Where:

Caribbean islands, Hispaniola, Haiti

When:

12 January 2010

Boundary:

Enriquillo-Plantain Garden fault system, where the Caribbean plate meets the Gonâve Micro-plate

Boundary type:

Conservative plate boundary

What happened:

There was a magnitude 7.0 earthquake on the Richter scale with an epicentre near the town of Léogâne, approximately 25 km west of Port-au-Prince. There were 52 aftershocks all greater than 4.5

on the Richter scale from 12th – 24th January. It caused a tsunami which there were an alert but was immediately cancelled

Effects:

Effect DescriptionPeople effected 3,000,000 people

Killed 90,000-300,000 peopleInjured 300,000 people

Homeless 1,000,000 – 1,800,000 people

Buildings damaged 300,000 buildingsIn some places 90% of buildings destroyed1,300 schools and 50 health care facilities were destroyed

Roads Many roads blocked with debris

Communications There was severe damage to the communications infrastructure with all TV and telecommunications cut off

Disease There was also diseases easily spread through the country with as severe outbreak of Cholera after the earthquake

Management

There were make shift shanty towns built for the millions of homeless Due to the masses of bodies there where mass graves built for all the bodies or they were

burned Orphanages was destroyed so families in the US adopted 400 children from Haiti The Dominican republic sent cook trucks to help supply food

Response:

There was a lot of aid from other countries with the Dominican republic giving first with food, water and heavy lifting machinery, also hospitals were made available for the wounded

Many countries arrived with aid and people to help such as doctors and cooks to help with the recovery

American red cross raised £4million in 24 hours for the Haiti effort A hospital ship was sent to help with the recovery There were around 100 planes every day sent to help with the relief effort Roughly £1 billion was donated to Haiti which was enough to give every family £22,000 each

Kobe earthquake

Also known as the Great Hanshin earthquake

When: Tuesday, January 17th 1995, at 5.46 am local time

Where: Kobe, Japan

Plate boundaries: Philippines plate sub-ducts under the Eurasian plate but Kobe lies also on a third boundary with the pacific plate which also sub-ducts underneath the Eurasian plate.

What happened: An earthquake of magnitude 7.3 beneath Kobe at a shallow depth of 16km. the earthquake hit Japan’s second most populous city with 10 million people living there, it lasted for 20 seconds. The ground move 1m vertically and 0.5m horizontally. There were a big outbreak of fires all over the city which caused most deaths there were also over 1,300 aftershocks. There were also some liquefaction.

Impact DescriptionPeople killed Over 6,300

Injured 40,000Infrastructure Roads blocked by debris and the Hanshin

Expressway, motorway built on stilts toppled over. Railways were also buckled and station damaged so bullet train was out of service.

At the port 120 out of 150 ships were destroyed and most of the cranes fell or

tilted making the dock not usableBuildings There were 200,000 building collapsesUtilities All utilities such as electricity, telephones

and gas where shut down to prevent further damage but some gas still leaked which

caused over 150 fires which killed over 1,000 people.

Homeless 300,000Industry Many of the factories such as Mitsubishi

closed for a couple weeksCost $100 billion or 2.5% of GDP

Insurance Only 3% of the city had earthquake insurance

Management:

Many of the public systems such as electricity, gas etc where back up and running by the following July, along with most of the rubble from the earthquake

All the trains were up and running again by August.

30,000 troops were sent to assist with the cleanup 250 trucks of bottled water was sent into the city Buildings such as schools were turned into temporary accommodation for 270,000

people.

Response

The people of Kobe learned from the catastrophe by improving the safety standards of their buildings, making sure they were made of earthquake-proof also fire-proof materials, making sure that the buildings were built on solid rock, and ensuring that all houses and buildings would be able to absorb shocks well.

There were more seismographs and other machines installed in order to better keep track of how the earth was moving, so they would be better prepared next time.

The highway had rubber blocks to help absorb the shock installed Buildings were built further apart so less likely to collapse onto each other. Many people moved away from a city to a area less prone to earthquakes Many old buildings collapsed so newer earthquake proof buildings were built in their

place.