IGCSE Plate Tectonics and GCSE Plate Tectonics


Specification:

2.1 Plate tectonics
Candidates should be able to:
• Describe the general distribution of fold mountains, volcanoes and earthquakes and explain how this distribution is related to movements at plate boundaries.
• Show a basic understanding of plate tectonics, describing the global pattern of plates, their structure, and be aware of plate movements and their effects – constructive (plates moving away from each other), destructive (subduction) (plates moving towards each other) and conservative (plates sliding past each other).
• Demonstrate an understanding of the main features of volcanoes (and their eruptions) and earthquakes.

2.4 Interrelationships between the natural environment and human activities
Candidates should be able to:
• Demonstrate an understanding that the natural environment presents hazards and offers opportunities for human activities. Reference should be made to the hazards posed by volcanic eruptions, earthquakes, tropical storms, flooding and drought.


The topic of plate tectonics is largely based on Alfred Wegner's theory of continental drift. Wegner was a German geophysicist and meteorologist who in 1912 hypothesized that the world's continents were moving. However, because he could not prove his theory, it was not accepted until the 1950's. His hypothesis was largely based on observations made of the shapes of the world's continents - he noticed that most appeared to fit together like a jig-saw e.g. Africa and South America. The theory late became accepted with the discovery of sea floor spreading in the Atlantic Ocean and fossil, flora and geological studies in Africa and South America. The movement of the earth's crust is now generally known as plate tectonic theory.

Structure of the Earth


The Earth is divided into four main layers, the crust, the mantle, the outer core and the inner core.

Crust: The crust is solid and is the layer we live on. The crust is usually between 10km and 60km thick. The crust thickness is often referred to as the relative thickness of an apple skin (when compared to the size of an apple).

Mantle: This the thickest section of the earth with a diameter of about 2900km. The mantle is often described as being semi-molten, but in reality the top is hard rock and as you near the outer core it is beginning to melt (magma). Convection currents are found in the mantle.

Outer Core: This layer is believed to be liquid and largely made of iron and nickel. It is extremely hot with temperatures up to 5,500 degrees centigrade.

Inner Core: This layer is believed to be solid, because of the immense pressure placed upon it. It contains the centre of the earth which is about 6,378km from the surface. It is also extremely hot at about 5,500 degrees centigrade.

Sometimes you will here the crust and the upper layer of the mantle referred to as the lithosphere. Below the lithosphere but also in the mantle you find the asthenosphere. This region lies between 100km and 200km. You do not need to remember these two terms in your exams.
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During the plate tectonics topic we will mainly focus on process taking place on the crust, but also the process of convection currents in the mantle.

Tectonic Plates and the Earth's Crust


The crust of the earth is broken into giants pieces. These giant pieces are called tectonic plates, or often just plates. There are seven major or primary plates (African, Eurasian, North American, South American, Pacific, Indo-Australian and Antarctica). There are seven smaller secondary plates (Nazca, Cocos, Caribbean, Scotia, Arabian, Philippine and Juan de Fuca). Because the plates are so big they have faults and cracks in them so are sometimes divided into smaller tertiary plates as well. The earth's plates are being constantly moved by convection currents found in the mantle. We will learn next what convection currents are and how they have changed the shape of the earth.

There are two types of crust, oceanic and continental. Generally oceanic crust is found under the oceans and continental under land. Although plates are usually a combination of oceanic and continental crust, there are some key differences between the two types of crust. the key differences are listed below.
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OCEANIC CRUST

CONTINENTAL CRUST

Oceanic and Continental Crust

  • Oceanic crust is younger
  • Oceanic crust is normally thinner
  • Oceanic crust is denser (heavier)
  • Oceanic crust can be destroyed
  • Oceanic crust can be made
  • Continental crust is older
  • Continental crust is normally thicker
  • Continental crust is less dense (lighter)
  • Continental crust can't be made
  • Continental crust can't be destroyed.
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Shifting Continents and Convection Currents


225 million years ago all the continents are believed to have been joined together in one supercontinent called Pangaea. Over millions of years, convection currents started moving the continents apart until there were two continents; Laurasia and Gondwanaland. Today the continents have moved even further apart, creating the land masses that we know today. The continents have not stopped moving so in the future the world will look different again, for example Europe and North America are actually moving apart at up to 10cm a year, but North America and Asia are moving closer together.

The tectonic plates are being moved by convection currents found within the mantle of the earth. Below is a summary of how convection currents work:
  • Magma (semi-molten rock) near the outer core is heated.
  • As the magma warms it expands and becomes less dense.
  • The less dense magma then starts to rise towards the crust
  • As the magma nears the crust it begins to cool.
  • The cooling magma becomes denser and begins to sink
  • The rising and falling magma creates circular currents with the mantle
  • It are these currents that create friction with the crust above and causes it to move.
  • The process is known as convection currents
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Plate Boundaries (earthquakes and volcanoes)


Where two plates join, it is called a plate boundary. Plates may move towards each other at a boundary, away from each other or alongside each other. If you look at a map showing plate boundaries and earthquakes and volcanic activity there is a very strong relationship. Below we will look at plate boundaries and learn why there are earthquakes and volcanoes found at plate boundaries. Below are maps showing plate boundaries and earthquakes and volcanoes.
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Map of Recent Earthquake Activity
Map of Recent Earthquake Activity

Describing Distributions on a Map


When describing a map, always draw a compass next to the map indicating the eight major compass points (N, NE, E, SE, S, SW, W, NW). Doing this will help make your description a lot clearer. You should know the world's seven continents (Africa, North America, South America, Europe, Oceania, Asia and Antarctica) and the three major oceans (Atlantic, Pacific and Indian). With the eight compass points, seven continents and three oceans you should be able to describe most places on the earth. For example if I was describing the distribution of earthquakes I might talk about concentrations in:
  • the west coast of South America
  • the west coast of North America
  • the south of Europe
  • the middle of the Atlantic Ocean
  • The edge of the Pacific Ocean
If you are confident with your country knowledge you can make your descriptions more detailed by also using countries, for example:
  • East and south east Asia, including Japan, Indonesia and the Philippines.

By looking at the two maps above you should be able to see that there is a very strong correlation (relationship) between plate boundaries and earthquakes and volcanoes. Earthquakes and volcanoes are basically found on or next to plate boundaries. As with most things there are a few exceptions and you should mention these in any description. For example:
  • There is a volcano in the middle of the Pacific Ocean (Hawaii)
  • There are earthquakes in the middle of Australia

Earthquake: A series of vibrations or movements in the earth's crust.

Volcano: A vent (hole) in the earth's surface where magma (lava), gas or ash escapes onto the earth's surface or into the atmosphere.

Ring of Fire: The large concentration of volcanoes found around the edge of the Pacific Ocean. El Salvador is located on the ring of fire.

Intra-plate Earthquakes: An earthquake found in the centre of a plate.

Hot spot: Basically an intra-plate volcano caused by a weakness in the earth's crust or particularly hot magma rising to the surface and breaking through the crust. Hawaii sits on and has been created by a hotspot.

Plate Boundaries


Plate boundaries can be classified in several ways. Plate boundaries where plates are moving towards each other, are called convergent, plate boundaries where plates are moving apart are called divergent and plate boundaries where plates are moving alongside each other are called transform. However, at IGCSE we need to know the specific names of plate boundaries. You need to know four types:
  • Constructive
  • Destructive
  • Collision
  • Conservative
Constructive Plate Boundary (sometimes called mid-oceanic plate boundary)

At a constructive or divergent plate boundary two oceanic plates are moving apart. Constructive plate boundaries are found under the ocean e.g. Atlantic Ocean and cause the process of sea floor spreading (basically the ocean floor getting wider). The movement apart of the plates allows magma to escape from the mantle below. When the magma touches the ocean it cools and forms new land creating an oceanic ridge. The world's best example of an ocean ridge is the Mid-Atlantic ridge. Overtime ridges can break the surface of the water and form new islands e.g. Iceland. Because the plates are moving apart, there is not a large build of friction so earthquakes tend to be fairly gentle. Volcanoes tend to be less violent than at destructive plate boundaries but can be more constant. Volcanoes can also cause the problems of lahars in Iceland. This is basically the lava melting the snow above and causing a mudslide.
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Destructive Plate Boundary

A destructive or convergent plate boundary is when oceanic and continental crust collide. The denser oceanic crust is forced (subducted) under the continental plate. Huge amounts of heat from the mantle and also friction cause the oceanic plate to start melting in the subduction zone. The continental plate can not be destroyed so is forced up to make fold mountains e.g. Andes in South America. As the oceanic plate melts, it expands, becoming less dense. This causes some of the magma to rise to the surface through the fold mountains creating volcanoes. Where the oceanic plate subducts under the continental plate a very deep ocean trench is created. This is basically a deep valley in the sea. Ocean trenches are the deepest sections of the world's oceans. Big earthquakes are found at destructive plate boundaries because of the build up of pressure between the two plates.

If a destructive plate boundary is found at sea, the continental crust (or less dense oceanic crust) is forced up to make an island arc instead of fold mountains. There are many examples of island arcs including the Caribbean, Indonesia, Japan and New Zealand.
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Collision Plate Boundary

A collision or convergent plate boundary happens when two continental plates collide. Because neither plate can be destroyed they are forced upwards and downwards. The upwards section make fold mountains (the Himalayas were made like this) and the downwards section makes mountain roots. You get big earthquakes at collision boundaries because there is a massive build up of friction and pressure. However, because no plate is being destroyed, magma is not being created, so you do not get volcanoes.
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Conservative Plate Boundary

A conservative or transform boundary happens when two continental plates move alongside each other. Because plates are not being forced up or down, there are no major landforms found at these boundaries. Also because crust is not being destroyed, no magma is being created so there are no volcanoes. However, there can be a huge build up of pressure between the two plates so massive earthquakes do occur. The most famous conservative plate boundary is the 'San Andreas Fault' where the North American and Pacific plates are moving past each other.
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Type of Plate Boundary

Types of Crust

Direction of Movement

Major Landforms

Tectonic Activity

Constructive

Oceanic and oceanic
Away from each other (divergent)
Ocean ridges and islands
Small earthquakes and volcanoes

Destructive

Oceanic and continental
Towards each other (convergent)
Fold mountains (with volcanoes) and ocean trenches and island arcs if boundary at sea
Big earthquakes and big volcanoes

Collision

Continental and Continental
Towards each other (convergent)
Fold mountains and mountain roots
Big earthquakes

Conservative

Continental and Continental
Alongside each other (transform)
No major landforms are found
Big earthquakes

Rift Valleys

A rift valley is a type of divergent plate boundary. It happens when a continental plate starts pulling itself apart. The most famous rift valley is the Great African Rift Valley. Here the African plate is basically ripping in half along a fault that runs from Syria in the north down to Mozambique in the south. The rift valley is over 6,000km in length. As the plates pull apart the land in between the plates collapses creating a rift valley. Overtime this valley firsts fills up with lakes e.g. Lake Malawi and Lake Tanganyika and then sea e.g Red Sea. Eventually the East of Africa will be separated from mainland Africa by a new sea. As the plates pull apart magma is also able to escape from the mantle below, creating volcanoes e.g. Mount Kenya and Mount Kilimanjaro. Sometimes the rift valleys are called grabens and the remaining higher land horsts or block mountains. When the African plate finally rips in half the two plates will be known as the Somalian plate and the Nubian plate.
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Earthquakes


Earthquake: Any movement in the earth's crust. Thousands of earthquakes happen everyday, but most are so small they are not felt by humans.

Magnitude: This means how strong something is. Earthquakes are normally measured on the Richter scale.

Richter scale: This is the normal scale used to measure the magnitude (strength) of an earthquake. The Richter scale goes up to 10 (although the scale effectively endless). The strongest ever recorded earthquake was a level 9.5 off the coast of Chile in 1960. The recent Japan (2011) earthquake was a 9.0.

Hypocentre (focus): This the actually location that an earthquake takes place. The focus is always underground in the crust.

Epicentre: This is the location on the surface directly above the hypocentre (focus).

Aftershock: This is an earthquake that happen after the main earthquake. If the initial earthquake is strong, then the aftershocks can be very strong. Japan has had several aftershocks of over 7.0 since the initial 9.0 earthquake.

USGS: The United States Geological Survey records all the world's earthquake activity. You can view recent earthquake activity at the following link. USGS - Recent world earthquakes

Secondary hazards: This a hazard that is caused by the primary hazard. Secondary hazards can sometimes be more dangerous than the primary hazard.

Earthquakes can cause several secondary hazards, that can often be more damaging than the primary hazard. Secondary hazards caused by earthquakes include:
  • Tsunamis
  • Dam failure
  • Landslides
  • Fires
  • Disease
  • Exposure
  • Liquefaction

Earthquakes are extremely hard to predict because they give no warning and the first earthquake is normally the strongest. Scientists (seismologists) look at earthquake history an attempt to identify plate pressure points to ascertain where earthquakes are likely to happen, but they can not predict how strong they will be or where they will happen.

Living Near Earthquakes


There are many places where people live in tectonically active locations e.g. Japan, West Coast of US (San Fransisco and Los Angeles), Central America and Chile. People living in tectonically active locations for a number of reasons including:
  • Poverty: Some people are very poor and are forced to live on marginal land that is very vulnerable to the impacts of earthquakes:
  • Inertia: Some people have lived in earthquake zones although their life an are unwilling to move
  • Infrequency: Major earthquakes happen relatively infrequently so some people are prepared to take the risk and don't think that one will occur in their lifetime.
  • Overpopulation: Some countries are very densely populated so people are forced to live on dangerous and marginal land.
  • Building Design: Building design has improved and now people are confident that their house or workplace will withstand strong earthquakes.
  • Education and preparation: Many countries practice earthquake drills and evacuation and prepare their houses so feel confident that they will know what to do in an earthquake.
  • Economic Opportunities: Many tectonically active locations have good resources and locations e.g. next to the sea. Because of this there are many job opportunities which people move near to take advantage of.

The affect an earthquake has on humans can depend on numerous human and physical factors. These factors include:
  • The depth of the earthquake
  • The magnitude of the earthquake
  • The duration of the earthquake
  • The local geology (soft or hard rock, solid or cracked rock)
  • The location of the epicentre (in a rural or urban area)
  • The population density around the epicentre.
  • The building design and hazard mapping near the epicentre.
  • The time of day (earthquakes at night might trap people in their houses, earthquakes during dinner time might trigger more fires).
  • The preparedness of the population (evacuation routes, emergency services, etc.)

Volcanoes


Volcano: A crack or hole in the earth's surface that allows magma, ash, gas or steam to escape to the surface.

Magma: Molten (melted) rock under the crust.

Lava: Molten rock on the surface of the earth.

Crater: The giant hole left by a volcanic eruption. Craters sometimes fill in with water to make crater lakes.

Magma Chamber: An underground store of magma.

Vent: A long tube or pipe that allows magma to escape to the surface.
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Viscosity: How thick something is. If you describe lave as being viscous, then it means that it is thick.

Eruption (Erupting Volcano): A volcano that is currently releasing lava, ash or gas.

Active Volcano: A volcano that has erupted recently.

Dormant Volcano: A volcano that has not erupted in recent history but may erupt again in the future.

Definitions for dormant and active vary, depending on what you read. Many definitions talk about active volcanoes are volcanoes that have erupted recently or erupted in reordered history. When you talk geologically though (life time of the earth), recent can mean thousands of years.

Extinct Volcano: A volcano that is unlikely to ever erupt again, because no magma is being produced under it. Often volcanoes that have not erupted for 10,000 years are considered to be extinct.

Acid Volcano

Acid volcanoes are formed by viscous (thick) lava. Because the lava is very thick, it does not travel far before it sets (goes hard and turns to rock). This creates a very classic steep sided volcano shape.
Basic volcano

A basic volcano is created by much more runny (less thick/viscous) lava. Because the lava is less thick, it travels further before going hard. This creates a much gentler (less steep) shaped volcano.
Composite Volcano

Composite volcanoes are caused by alternative eruptions of ash and lava. Again these processes produce a fairly classically shaped volcano.
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Types of Volcanic Hazards


Types of Hazards

Volcanoes can create a number of primary hazards as well as some secondary hazards. Primary hazards include lava flows, pyroclastic flows and volcanic/lava bombs. Secondary hazards include tsunami, acid rain and lahars.
Volcano Explosivity Index (VEI)

Developed in 1982 by the USGS it was designed so volcanoes could be given a magnitude. Volume of products, eruption cloud height, and qualitative observations (using terms ranging from "gentle" to "mega-colossal") are used to determine the explosivity value. The scale is open-ended with the largest volcanoes in history given magnitude 8. The scale is logarithmic, with each interval on the scale representing a tenfold increase in observed eruption criteria (exception: between VEI 0 and VEI 1).
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Lava Flows: Most traditionally associated with volcanoes, but probably one of the least dangerous hazards to humans. Lava flows only travel up to a couple of km/hr so it is possible to move out of their way. However, they can bury and incinerate any land or property that they travel over.
Pyroclastic Flows: These are giant clouds of ash and gas. They are extremely dangerous because they can travel up to 500 km/hr, reach distances of 30km and can be over 700 degrees centigrade in temperature. They will burn, knock over or bury anything in their path.
Lahars: These are a secondary hazard and normally occur on snow covered volcanoes. Hots ash and gas melt the snow and then mix. They then travel down the volcano as a fast moving mudflow which can drown or bury anything in their path.
Ash Clouds: Not as fast moving as a pyroclastic flow, but ash clouds can still be very disruptive. The weight of falling ash can collapse buildings and destroy crops. They can reduce sunlight by blocking out the sun and even cause problems for air travel like the recent Iceland volcano.
Lava or Volcanic Bombs (tephra): When volcanoes erupt they often throw out semi molten pieces of rocks. As long as humans are a safe distance they don't really pose any problems. However, because of their heat they can start fires.
Poisonous Gases: When volcanoes erupt they can release poisonous gases like carbon monoxide and sulphur dioxide. These can kill humans or animals if they are too close, but they can also contribute to the greenhouse effect.
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Volcanoes are a lot easier to predict than earthquakes because they normally give some warning signs. Scientists (vulcanologists) will look for some of the following changes to try and predict a likely volcano.
  • Change in the shape or size of volcano
  • Change in the temperature of a volcano
  • Change in the amount and type of gases being released
  • Earthquake activity
  • Changes in plant and animal life
  • Changes in local hydrology e.g. temperature and chemical composition of nearby rivers.

Living Near Volcanoes


Even though volcanoes are extremely hazardous places, many people still choose to live on, or near them. Some of the reasons why people do this include:
  • Their beauty, places like Mount St. Helen's are beautiful to look at and enjoy.
  • Minerals, it is possible to mine minerals like sulphur from volcanoes
  • Geothermal potential (cheap and clean renewable energy) e.g. Iceland.and El Salvador
  • Tourism - tourists like to view and walk up volcanoes e.g. Santa Ana volcano or Pacaya volcano
  • There is often hot springs near volcanoes which tourists and locals can enjoy e.g. Mt. Arenal in Costa Rica or the hundreds of onsens in Japan.
  • Land around volcanoes is very fertile because of all the minerals, therefore many people choose to farm the land.
  • Poverty, people simply can't afford to live anywhere else apart from the marginal land on volcanoes
  • Complacency or naivety because the volcano has not erupted for a long time.
  • Confidence that they will be given adequate warning to evacuate
  • Family home. Family have always lived in the area and don't want to leave
  • Shortage of space and high population density. San Salvador is slowly growing up El Boqueron because of the shortage of space.

Mount Arenal Volcano in Costa Rica (tourism)

Mount Arenal is Costa Rica's most active volcano. It has been erupting on and off since 1968. Around the volcano and especially in the nearby town of La Fortuna, hundreds of jobs have been created by people visiting the volcano hoping to see it erupt. There are now close to 100 hotels in the area as well as horse riding stables, mountain biking, canopy trails, nature reserves, rafting centres, restaurants, quad biking and much more. A large number of hot spring resorts have also developed in the area.
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Geothermal Power in Iceland

Iceland sits on a constructive plate boundary in the middle of the Atlantic Ocean. Iceland itself was actually created by magma escaping from the mantle. Iceland has five geothermal power stations that create 24% of Iceland's energy needs. In addition geothermal power heats the houses and water of 87% of buildings in Iceland. In addition to heating and geothermal power, volcanic activity has also created a large tourism industry and created a number of hot springs, including the world famous Blue Lagoon (see below).
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Mount St. Helens Natural Beauty

Mount St. Helens is located in the Cascades mountain range in the Rockies. It sits on a destructive plate boundary. Mount St. Helens lies in a beautiful area, the mountains themselves are beautiful but also Spirit Lake at its foot. Mount St. Helens has become home to people who like the outdoors. It has also become a tourist destination and is good for fishing. People feel relatively safe living near the volcano because it is so well monitored. However, despite warnings over 50 people still lost their lives in the 1980 eruptions. Most would not leave either because they were scientists studying the volcano or residents who could not bring themselves to leaving their home.
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El Boqueron, San Salvador

El Boqueron has created a number of benefits for local residents. The fertile slopes on the side of El Boqueron has allowed coffee farming to take place. Also the road up the side of El Boqueron has increased tourism, both to visit the restaurants, visit the view points and look at the crater and wildlife. More people are also choosing to live on its slopes because of shortage of space in downtown San Salvador, but also because it is cooler, safer (in terms of criminality) and less congested. Because El Boqueron has not erupted for nearly 100 years, citizens feel safe living under it.
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Volcano Preparedness and Reaction

  • Diversion channels: On some volcanoes it has been attempted to make diversion channels to direct the lava away from settlements. This is very expensive and hard because you can not predict which direction the lava will flow.
  • Cooling lava: In Iceland in the past they have tried spraying seawater onto lava. The idea was to make the lava go cold and turn into rock before it destroyed nearby settlements.
  • Sweeping roofs: During ash showers it is very important to regular sweep ask off rooves. If this is not done the ash will get so heavy that it will eventually cause the building to collapse.
  • Making evacuation routes: It is very important to plan evacuation routes for individual houses and whole settlements. It is also important to regularly practice these evacuation routes.
  • Exclusion areas: If an eruption is happening or likley to happen it is important to create exclusion zones. This means evacuating everyone that could be effected by the eruption. Because pyroclastic flows can travel up to 30km, these exclusion zones can be very big.
  • Hazard Mapping: It is very important to map the most dangerous areas near a volcano e.g. areas with the most unstable ground or areas where lava flows are likley to travel. Once you have mapped dangerous areas you can then stop settlements being built on them.
  • Monitoring volcanoes: Because volcanoes do give warning signs (change in shape, temperature, etc.) it is very important to monitor them carefully so that you can nearby residents warnings.
  • Looking at volcanic history (previous eruptions and flows): As part of monitoring the volcano you can look at its history and previous flows. You can then try calculate frequencies and areas likely to be effected.
  • Volcanic Plug: You can attempt to make an artificially volcanic plug by dropping boulders or concreter into a crater or vent. This is dangerous and unlikley to be successful. In fact it might build up the pressure in a volcano and cause a more violent eruption.

Plate Tectonics Case Studies

Mount St. Helens Volcano

Mount St. Helens is located in the Cascades mountain ranges which is part of the North American Rockies. It sits on a destructive plate boundary where the Pacific plate and Juan de Fuca plate subduct under the North American plate. Mt St. Helens had been dormant for nearly 120 years when on the morning of 18th May 1980 a 5.0 earthquake triggered a huge landslide and pyroclastic flow. The pyroclastic flow travelled for 25km and flattened everything in its path. Ash and gas continued to be released from the volcano over the course of the day and reached the east coast of the US three days later.

Sixty one people lost their lives in the tragedy, mainly residents refusing to leave and scientists monitoring the volcano. Spirit lake was destroyed along with 250km of fishing rivers. 250km2 of forest was destroyed and 10 million trees had to be replanted. No animals survived in the blast zone and many crops were destroyed by falling dust.

To learn about some of the impacts and responses, visit the BBC Bitesize page below:

http://www.bbc.co.uk/schools/gcsebitesize/geography/natural_hazards/volcanoes_rev7.shtml
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Kobe 1995 Earthquake

Japan is located in East Asia and sits on a destructive plate boundary. At the boundary the Pacific and Philippine plate are subducting under the Eurasian plate. On the 17th January 1995 a 7.2 magnitude earthquake hit Kobe, the earthquake lasted for 20 seconds. The focus of the earthquake was very near the surface and the epicentre almost under Kobe.

200,000 building collapsed as well as road and rail bridge. Kobe port was mostly destroyed. The earthquake caused many secondary effects including power failure, fires, homelessness and congestion. The final death toll from the earthquake is believed to 5,500 but the cost of damage ran into billions of dollars.

Kobe being in an MEDC recovered amazingly quickly. Rail services were back to normal by August, a year later 80% of the port was reopened, water and electricity were back on by July and all the damaged buildings were rebuilt stronger.
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Afghanistan 1998 Earthquake

Afghanistan is located in South Asia and sits on a collision plate boundary. The Indian and Iranian plate are colliding with the Eurasian plate. Although this does not cause any volcanoes, it does cause very big earthquakes. On 4th February 1998 northern Afghanistan was struck by a 6.1 magnitude earthquake. The province at the epicentre was Takhar which is a remote province with poor transport and communications.

Reports of the earthquake took three days to reach the capital Kabul. A day later a number of international charities reached the area and stated that over 20 villages had been destroyed and up to 4000 were dead. It was not until 16th February that weather had cleared enough for emergency helicopters to reach the area. When helicopters reached the area, it was discovered a further 7 villages had been destroyed, 10,000 people were injured and a further 15,000 homeless.

Even though the earthquake to hit Afghanistan was not massive, it still caused a lot of death and damage. This is because Afghanistan is one of the poorest countries in the world which has suffered conflict for decades. Much of Afghanistan is mountainous and transport and communication links are poor. There is little money to spend on medical care and there were no trained rescue services - Afghanistan had to rely on outside help. Building design in Afghanistan is also poor and much of the adult population is illiterate.
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Comparing Vulnerability to Hazards in MEDCs and LEDCs

Preparedness and Vulnerability in MEDCs

Preparedness and Vulnerability in LEDCs

  • Many MEDCs do hazard mapping and zonal planning. They will assess the risk for different areas of the country e.g. is it likely to flood or be in a lava flow. They will then only allow low value and low risk land uses in hazardous areas.
  • Most MEDCs have fairly strict building codes to protect against earthquake damage. Buildings will have to be reinforced, have shatter proof windows, dampers, sprinklers and escape routes.
  • In MEDCs the entire population will be educated about hazards. They will know what potential hazards there are and how to respond to them. People will be told evacuation routes and where safe areas are.
  • Emergency and rescue services will be trained so they know how to find victims and how to treat them. They will have proper equipment and carry out practices.
  • Hazards will be better monitored in MEDCs, scientists will study volcanoes, track hurricanes and then try and make accurate predictions and inform the public.
  • Transport and communications are usually much better. The population can be informed and are more easily able to escape. There are likely to be more helicopters which can be essential in search efforts when roads are damaged.
  • MEDCs are simply richer so they can afford to spend more money on training and preparedness.
  • There will be stockpiles of tents, blankets, food and water for anyone who has lost their home and possessions.
  • LEDCs tend to have more informal settlements that don't follow building codes. This makes them more vulnerable when hazards hit.
  • Many LEDCs suffer from rapid urbanisation and uncontrolled growth of settlements on dangerous marginal land.
  • Medical care will be poorer in LEDCs and there will be less money spent on search and rescue teams.
  • Many LEDCs rely on emergency aid during times of natural disasters. Emergency aid always takes several days to mobilise which will usually cost lives.
  • Transport and communication will be poorer in LEDCs. Much of the population will not have access to phones, television or the internet so will not be warned about forthcoming natural disasters.If they do know, lack of adequate transport may make escape difficult. There will certainly be a shortage of helicopters.
  • There probably won't be adequate supplies of tents, blankets, food and clean water.
  • Services like electricity and water will take longer to repair, leading to the secondary hazards of diseases and exposure.
  • A lot of population will be illiterate and never taught about potential natural disasters and how to respond to the natural disasters.
  • Less money will be spent on monitoring potential hazards, because countries have less money and less trained scientists.
  • Evacuation routes may not exist and there may be as shortage of shelters.
  • Poor LEDC cities often have very high population densities. This causes more people to be effected by the primary and secondary hazard.

Building Design and Building Preparedness

Buildings can be made safer in a number of ways. Firstly they can be built in areas less vulnerable to hazards e.g. flat land with solid rock. They can then be designed to be made stronger, cross braces can be used to make the building stronger, dampers can be added to high buildings to counteract swing in earthquakes or even springs can be added to foundation to allow buildings to move. Once a hose is built pictures can be secured to walls, windows reinforced and emergency exits created. Read the attached booklets to see how the American government recommends schools and houses to prepare.


external image earthquake_0.jpg
external image earthquake.jpg

Short-term and Long-term Effects of Disaster

SHORT-TERM EFFECTS

LONG-TERM EFFECTS

  • Death: There will often be large numbers of people who have been killed in the initial disaster. This will obviously lead to grieving families, but also the bodies need to be cleared before disease starts to spread.
  • Injury: Many people will be injured in the initial hazard and these people will need to be treated. This uses precious resources and costs money.
  • Panic and Fear: After a major hazard people will be scared of a repeat disaster. For example earthquakes usually have aftershocks which can cause further buildings to collapse.
  • Secondary hazards: Short term secondary hazards like fire might damage large areas or even kill more people after a disaster. There may even be further primary hazards like aftershocks.
  • Infrastructure damage: Electricity, water, transport and communications links will all be damaged hampering search and rescue efforts and leading to further secondary hazards like food shortages.
  • Homelessness: Destroyed homes can take months and even years to rebuild.
  • Unemployment: Many industries and businesses get destroyed during disasters so people lose their jobs. However, some jobs will be created in rebuilding efforts.
  • Dependency: Countries who have suffered a disaster will normally see their income decline. This makes them more reliant on international aid and foreign countries.
  • Long-term injuries: Some injuries can take months or even years to heel e.g. fractures and paralysis. Therefore some victims will need long term care.
  • Disease: A major secondary hazard is often disease. Disease normally starts because of dirty and temporary living conditions and dirty water. These effects can go on for years until houses are rebuilt and water reconnected.
  • Post traumatic stress disorder: People who have experienced disasters or lost loved ones will experience psychological problems long term.
  • Rebuilding Costs: Eventually roads, houses and businesses will all have to be rebuilt. This is very expensive and the money will have to be diverted from other areas e.g. education. Countries may also have to raise taxes or go into debt to pay for the recovery.
  • Infrastructure damage: A lot of infrastructure will be damaged long-term making recovery very hard.
Countries who have suffered disasters find it hard to recover because:
  • Death - many people will have been killed so there are less workers and less money being generated.
  • Injury - There will be many people injured, some with long term injuries. Therefore there will be less workers and more money transferred to treat injured.
  • Damaged transport links - Roads, ports and airports might all be damaged, so people will find it harder to travel to work and the country will find it harder to import and export.
  • Damaged communications - Phone lines and internet links are often damaged during disasters and communications remaining are often overloaded. Without communications many businesses find it hard to operate and governments will find it hard to coordinate recovery efforts.
  • Loss of income - Because businesses will have been damaged and there are less workers, the country will see a fall in income so will have less money to spend on recovery.
  • Psychological impacts - Many citizens will still be fearful of further disasters so are too scared to return to work. Others will be grieving for friends or relatives so are unable to work fully.
  • Shortage of food and water - Food production and water supply are often effected by disasters. This can lead to illness and also malnutrition (weakness from shortage of food). If you have weak and ill people, the recovery will be slower.
  • Electricity shortages - Electricity generation and supply are often damaged during disasters. Most businesses, equipment, etc. need electricity to operate. If there is no electricity, then the recovery will be slowed.
  • Damaged equipment - Equipment as well as people and buildings can be damaged in disasters e.g. diggers or cranes. If equipment is damaged then it will need replacing before it is possible to rebuild.
  • Damaged buildings - Many buildings including important power stations, hospitals and government buildings can be damaged during disasters. If you are lacking power and important administrative centres the recovery will be made harder.




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