OCR A-Level Geography - Hazardous earth Flashcards
What are the 3 layers of the Earth?
Crust
Mantle
Core (inner and outer)
What separates the crust and the mantle?
Moho
What 2 layers does the upper mantle consist of?
Lithosphere (semi-core)
Varies in thickness
Boundary with asthenosphere difficult to define (melts and becomes incorporated in asthenosphere)
Asthenosphere extends 100-300km
Semi-molten/viscous - Allows rock to move due to high pressure in mantle.
Flowing slowly
What are continental and oceanic plates made up of?
Lithosphere and crust
Where do convection currents exist?
What do these do?
Asthenosphere
Caused by vast amounts of heat generated in mantle.
Semi-molten asthenosphere flows carrying with it the solid lithosphere and crust.
What are the properties of the continental crust?
Thickness:
35km average (<30-70km)
Density:
2.6-2.7
Mineral composition:
Mainly granitic, silicon, aluminium
What are the properties of the oceanic crust?
Thickness:
5-10km
Density:
3.0
Mineral composition:
Mainly basaltic, silicon and magnesium
What are the properties of the mantle?
Thickness:
To a depth of 2900km
Density:
3.3 at Moho
5.6 at core
Mineral composition:
Rich in magnesium and iron
Explain the movement of the crust caused by convection currents in the mantle.
Hot rock rises from lower to upper asthenosphere.
Hot rock spreads and cools, pushing plates apart.
Cool rock sinks back down towards core.
As (oceanic) plate subducts at ocean trenches, gravity pulls it under (slab pull).
Rising mantle pushes crust upwards at mid-ocean trenches, while gravity pulls it back down (ridge push).
What was Alfred Wegener’s big idea?
250 million years (Carboniferous period), all the Earth’s continents fit together (Pangea).
Over time, continents have moved apart through continental drift.
Explain 3 pieces of (Wegener’s) geological (rocks) evidence for continental drift.
Mountain chains and rock sequences on opposite sides of oceans show close similarities (e.g. northeast Canada and northern Scotland).
- These mountains are likely to have been created together and then split apart as the continents moved.
Continents seem to fit together (particularly South America and Africa).
- Suggests that continents once fit all together and continental drift has separated them.
- (Erosion wouldn’t’ve made them this shape).
Evidence of glaciations 290 million years ago in southern Africa, Australia, South America, India and Antarctica.
- Suggests these land masses were joined during this time, located close to the South Pole.
- (India has a tropical climate now, and due to it’s current location it wouldn’t have been glaciated in an ice age.
- Suggests India was one at a higher latitude further from the equator).
Explain 3 pieces of (Wegener’s) biological (living) evidence for continental drift.
Similar fossils of marine shellfish (e.g. brachiopods) were found in Australian and Indian limestones.
- Brachiopods are small shellfish that would be unlikely to cross open stretches of ocean between Australia and India.
- Suggests India and Australia were once much closer together meaning the brachiopods have been separated by continents moving apart.
Similar reptile fossils found in South American and South Africa.
- Reptiles wouldn’t’ve been able to cross the ocean suggesting all land was once joined together.
- They are unlikely to have evolved the same in separate areas.
*Fossil from rocks younger than Carboniferous period show fewer similarities between animal, suggesting they followed different evolutionary paths.
- These animals originally evolved together (during carboniferous period).
- Once the continents split the animals were separated.
- They evolved as their environments changed, becoming more different.
What is paleomagnetism?
Changes in the Earth’s polarity.
Occurs every 400,000-500,000 years
Explain why there are different bands of rock on the ocean floor.
(Paleomagnetism)
Describe the locations of the different bands of rock (old and new rocks).
It has been found that there are very small variations in the Earth’s magnetic field.
These can be explained by changes in the Earth’s polarity.
Oceanic crust and the ocean floor is made up of igneous rock which originated from lava flows and contains iron particles.
As lava erupts and cools, the magnetic orientation of iron particles is locked into rock, depending on the Earth’s polarity at the time.
Different bands of rock on the ocean floor have been found which are explained by the changes in the Earth’s magnetic polarity - rock changes direction and type with each change of polarity.
Oldest rock would be located furthest from the point it is created (nearer land).
Because new rock is being created from the centre point which forces older rock outwards (towards land).
What is sea-floor spreading?
Lateral movement of new oceanic crust away from a mid-ocean ridge (constructive plate boundary).
Explain the process of sea-floor spreading.
(Link to paleomagnetism)
Width of each strip of the ocean bed with the same magnetic orientation corresponded with the age of time scale of the magnetic reversals.
Indicates that, as fresh molten rock from asthenosphere reaches ocean bed, ‘older’ rock is pushed away from the mid-ocean ridge.
Sea-floor spreading moves material across ocean floors.
Eventually, the sea floor reaches an ocean trench where material is subjected into the asthenosphere and becomes semi-molten (caused by convection currents).
What is the evidence for sea-floor spreading?
Newest rock is found in the middle (at mid-ocean ridge), therefore new rock is being created here.
Rocks are not the same age as the earth (4.5 billion years) meaning oldest rock is being destroyed and replaced by newer rocks.
Global patterns of plate boundaries
Earthquakes are concentrated in narrow bands at plate boundaries (rigid lithosphere and crust broken up into tectonic plates that are moving).
What are the 3 types of plate boundary?
Divergent (constructive)
Convergent (destructive)
Conservative
Example of divergent (constructive) plate boundaries
Iceland (Eurasion and North American plate)
Mid-atlantic ridge (South American and African plate)
Great African rift valley (African plate)
What happens at divergent plate boundaries?
Plates move apart.
Convection currents rise and spread apart.
New crust is created.
Describe the movement of tectonic plates at a divergent boundary
Hot rock rises, cools and spreads.
Convection currents push plates apart.
Gap releases pressure.
Mantle rocks can melt, forming magma.
Magma erupts effusively.
New crust is created (basic lava - basaltic).
Ridge created.
Ridge push accelerates plate movement.
How is magma formed at divergent boundaries?
Asthenosphere (semi-molten rock) rises, pressure decreases towards crust so rock melts.
Plates moving apart creates a gap that relieves the pressure (less pressure).
Features of lava at divergent boundaries
Type: Basalt (runny)
Acidic/basic: Basic
Silica content: Low (thin, milk-like)
Temperature: High
Viscosity: Low (runny)
Frequency: High
Duration: Often
Why are volcanoes at divergent boundaries effusive? (smooth, gentle flows of lava - when lava has low viscosity)
Basic lava is runny (has low viscosity)
How does volcanic activity affect landforms on divergent boundaries?
Runny basaltic rock creates pillow lava formations (round igneous rocks) - eruption of magma occurs mostly underwater. Magma erupting directly onto sea bed is rapidly cooled which forms pillow lava.
Lava plateaux, e.g. Giant’s causeway.
Mid-ocean ridge formed by new crust (long chain of underwater mountains).
Low, flat shield volcanoes formed by runny lava.
Rift valley
What is a mid-ocean ridge?
Very long chains of mountains on the sea floor.
Altogether have a combined length of 60,000km.
At intervals, ridges are broken by transform faults.
Vary in shape depending on rate of spreading (determined by amount and rate of magma rising).
How does the spreading of plates cause earthquakes?
Transform faults
Small, shallow-focus earthquakes occur along their lengths as they slip.
What are transform faults?
Large-scale faults in the crust at right angles to a mid-ocean ridge, which range from tens to hundreds of km.
Why do divergent boundaries have shield volcanoes?
Lave flows far which forms low, gently sloping volcanoes.
Runny basic lava erupts gently.
Less viscous lava flows far (flows easily).
Creates wide, gently sloping volcanoes.
Describe the sequence of formation of a rift valley
(Underwater)
Rising magma creates dome/bulge.
Plates continue to spread.
Brittle rocks fracture and fault.
Dome subsides (sinks) forming a steep-sided valley.
E.g. African rift valley (African plate splitting apart).
Rift zones on land
Continental crust must be thin for rifting to occur.
E.g. Red Sea northwards to Turkey.
Crust has been stretched, causing faulting and forming a sunken valley known as a graben.
As rift widened, magma erupted to surface.
Eventually rift valley sank below sea level, forming the present-day Red Sea.
What are the 3 types of convergent boundary?
Why are there 3?
Oceanic-continental
Oceanic-oceanic
Continental-continental (collision)
Plates have different densities.
Continental: 2.6-2.7kg m^3
Oceanic: 3.0kg m^3
Example of oceanic-continental convergent (destructive) plate boundaries
Nazca plate -> South American plate
What happens at oceanic-continental convergent plate boundaries?
Convection currents cause plates to converge.
The denser oceanic plate subsides beneath the less dense continental.
Slab pull accelerates movement of oceanic plate.
Describe the movement of tectonic plates at a oceanic-continental convergent boundary
- Plates push together by convection currents.
- The more dense oceanic crust subducts beneath the less dense continental crust.
- Friction from plates rubbing together heats plates. Water from the ocean helps crust melt forming viscous acidic magma. Pressure builds up causing deep and shallow earthquakes.
- Magma forces through continental crust (viscous lava has explosive eruptions).
- Slab pull pulls subducting plate faster.
Volcanoes and fold mountains are formed near the edge of continental crust.
How is magma formed at oceanic-continental convergent boundaries?
Subduction brings volatiles (water + CO2) which cause melting of rock.
Features of lava at oceanic-continental convergent boundaries
Type: Rhyolitic (more acidic) /Andesitic (less acidic)
Acidic/basic: Acidic
Silica content: High (high silica = high viscosity)
Temperature: Lower
Viscosity: High (thick)
Frequency: Infrequent (struggles to break through crust)
Duration: Short
VIOLENT
Why do volcanoes at convergent boundaries build steeper slopes?
Acidic lava has a high silica content which makes it viscous (thick). Therefore it does not flow easily so builds up steep composite volcanoes (layers of rock and tephra).
Why do volcanoes at convergent boundaries erupt more explosively?
Pressure builds up over long periods of time due to high viscosity and slow flowing magma.
Describe and explain the formation of strato volcanoes (composite volcanoes)
Description:
Cone-like
Steep-sided
Have a crater at the top
Composite (made up of layers)
Have secondary vents
Layers of ash and acid lava built up over successive eruptions.
Lava intrudes into layers, forming sills (horizontal intrusion of magma) and dykes (vertical intrusions of magma).
Vents of volcano can be sealed by solidified magma/lava (plug).
This causes pressure to build up, resulting in explosive eruptions.
Magma erupts violently as air bubbles finally burst.
Throws droplets of lava as tephra and lava bombs.
E.g. Mount Etna, Italy
Describe and explain the formation of calderas
Description:
Basin
Explosive eruptions empty the magma chamber beneath the volcano.
The lack of support beneath causes the volcano to collapse on itself, forming a caldera crater.
Collapsing of volcano’s sides can cause tsunamis.
E.g. Krakatoa, India
Describe the causes of earthquake activity found at convergent plate boundaries
Two plates being pushed into one another which builds up immense amount of pressure.
Faulting and fracturing takes place in the benioff zone.
Causes pressure and energy to be released which creates earthquakes.
What is the benioff zone?
The boundary between the subjecting ocean plate and over-riding continental plate.
Seismic energy is released here as rocks fault and fracture.
What happens at oceanic-oceanic boundaries?
Slightly denser plate will be subjected.
What is formed at oceanic-oceanic boundaries?
Ocean trench where the denser plate subducts.
E.g. Mariana trench up to 10,994m deep.
Island arcs. As descending plates melt, magma is produce and rises to surface. Eruptions form chains of volcanoes.
E.g. Mariana islands up to 820m above sea level.
Describe the movement of tectonic plates at a oceanic-oceanic convergent boundary
- Convection currents push crust together.
- Denser oceanic crust subducts under less dense oceanic crust.
- Forming an ocean trench at the area of subduction.
- Volatiles help descending crust to melt and forms magma which rises and erupts forming island arcs.
- Composite volcanoes are formed from viscous acidic lava.
How does plate movement affect landforms and landscapes?
Creates deep ocean trenches and tall mountain ranges (island arcs).
How does volcanic activity affect landforms and landscapes?
Explosive eruptions form:
Strato (composite) volcanoes made up of layers of tephra and acidic lava which contain complex internal systems which create dykes and sills underground.
Caldera craters which appear as a large crater, group of small islands or as a large lake.
How does earthquake activity affect landforms and landscapes?
Fault lines and cracks can occur in crust as energy from earthquakes
Examples of continental-continental plate boundaries
Himalayas (Indo-Australian plate <-> Eurasian plate)
Why are continental-continental boundaries called ‘collision’ boundaries?
Because they collide.
They move together but aren’t dense enough to subduct.
Describe the movement of tectonic plates at continental-continental boundaries
2 continental plates converge.
Little, if any subduction occurs due to similar densities.
Accumulated sediments are compressed into rock which buckle and fold forming mountain ranges.
Explain why the plates are moving in this way at continental-continental boundary
Convection currents push plates together.
However they move slower because there is no slab pull or ridge push to accelerate movement.
Describe the causes of earthquake activity at a continental-continental boundary
Friction builds up at the collision zone. Rocks crack and fault and when pressure reaches the threshold energy is released as an earthquake.
Earthquakes are usually have a shallow focus and are of moderate strength. E.g. Nepal, 2015 (7.0MW)
How do collision boundaries affect landforms and landscapes?
Fold mountain chains are formed - total 2.5 million km.
Loss of ocean floor due to tectonic uplift.
Cracks and faulting in rocks.
Synclines and anti-synclines (bending of rock).
Example of a conservative plate boundary
San Andreas Fault California
Why are conservative boundaries named this?
Crust is neither created or destroyed, just conserved (slide past each other).
Describe the movement of tectonic plates (San Andreas Fault) at conservative plate boundaries
Plates move past each other.
Pacific plate (LA) moves north west by 5-9cm /year.
North American plate (San Fran) moves north west by 2-3cm /year.
Slab pull as crust subduct at different boundaries.
Difference in rate means North American plate moves south-east in relative terms.
Explain why no volcanic activity is found at conservative plate boundaries
No subduction or spreading occurs.
Rock doesn’t melt.
Therefore no formation and pressure build up of magma.
Describe the causes of an earthquake at a conservative boundary
- Plates do not move steadily (they move intermittently).
- Plates rub against each other creating frictional resistance and they sometimes get stuck.
- Pressure gradually builds up until it reaches the threshold.
- Rocks fracture and energy is released as shallow-focus earthquakes. Plates move in a ‘jolt’.
Describe features of an earthquake at a conservative boundary
Shallow-focus
Major
Lateral movements (P and love waves)
How do conservative boundaries affect landforms and landscapes?
- Do not create large landforms.
- Can create major faults across landscapes (San Andreas Fault).
- Landforms across the faults can also be displaced.
e.g. River channels deflected by movement of faults.
Example of a hot spot
Hawaiian islands
Middle of pacific plate
What is a hot spot?
A particularly hot section of mantle. This can melt through the crust causing volcanic activity.
Hot spots usually occur away from plate boundaries.
Some are found at plate boundaries, e.g.Iceland.
Describe the formation of volcanic Islands at a hot spot (Hawaii)
- Plume of particularly hot mantle.
- Melts through crust forming volcano and island.
- Movement of plate transports volcano away from hot spot.
- Volcano becomes extinct. New volcano formed at hot spot.
Oldest (smaller) island: Kauai (formed 3.8 million years ago)
Newest (bigger) island: Hawaii (big island)
Crust moves away from hot spot so it cools and becomes denser making it subside (sink).
Islands have been eroded by waves, weathering and mass movement making the older islands much smaller.
Volcanic activity at Hawaii is less viscous basaltic lava (has lower silica content).
Explain which type of volcano will be formed by eruptions at hotspots and why.
Shield, gently sloping, wide volcanoes.
Because basaltic lava is less viscous meaning it flows easily and flows further.
Effusive eruptions build huge volcanoes.
Describe the earthquake activity experienced at a hot spot
They are caused by a build-up of pressure and movement of ground due to volcanic activity.
Small earthquakes
Frequent
Caused by movement of magma
Most where hot spot it (Hawaii).
Explain the difference between hot spot volcano chains and island arcs found at convergent boundaries
Hot spot volcano chain
- Magma activity at hot spot
- Basic lava
- Effusive
- Shield volcano
- Formed in a sequence
- Big age difference
Island arcs
- Magma activity (subduction and volatiles)
- Acidic lava
- Explosive
- Strato volcano (composite)
- Closer together in age, less variation as they are formed together.
Example of a super volcano
Yellowstone, Wyoming
North American plate
What is a super volcano
A volcano that erupts more than 1000km^3 of material in a single eruption.
Are usually found as giant calderas.
They occur when rising magma cannot break through crust.
Pressure increases as more magma rises until magma violently forces its way through as a huge eruption.
Outline different Lava flows based on silica content
Basic (Basaltic)
Lava is free-flowing and can run for considerable distances.
Hawaii (July 2015) lava flow extended for 20km without stopping.
Acidic
Thick, pasty lava doesn’t flow easily.
Everything in the path of lava is burned/buried destroying infrastructure/properties/crops.
Rarely cases injuries/fatalities because people can escape the flow.
Volcanic eruptions generate distinctive hazards
…
Pyroclastic flows
Combination of hot gases (500degC+), ash and rock fragments travelling at high speeds (100km/hr).
Follow contours of ground and destroy everything in path.
Inhalation of hot, poisonous gas can result in almost instant death.
Tephra
Any material ejected from volcano into air.
Fine ash/volcanic bombs.
Buries farmland, destroying crops, disrupts transport on ground and in air.
Iceland’s volcanic eruption (2010) led to cancellation of 100,000 flights.
Builds can collapse due to weight of accumulated ash.
People with respiratory diseases have difficulty breathing.
Gas emissions
(CO, CO2, SO2)
Deadly threat to humans.
SO2 combines with atmospheric water, produced acid rain.
Enhances weathering can damage crops and pollute surface water and soils.
Lahars
Type of mud flow (consistency of wet concrete).
Travel up to 50km/hr.
Destroy/bury everything in it’s path.
Eruption in Columbia (1984) killed 23,000 due to lahars.
Floods
Volcanic eruptions beneath ice field/glacier results in rapid melting.
Iceland’s volcano lies beneath ice and snow.
Eruptions cause vast quantities of water to accumulate until it finds an exit.
Results in torrents of water, can cause devastating floods.
Tsunamis
Eruptions of island volcanoes cause displacement of ocean water creating tsunami waves that travel up to 600km/hr.
Tsunamis created by eruption of Krakatoa in 1883 believed to have drowned 36,000 people.
What is the volcanic explosively index?
A measurement used to rank and compare different volcanic eruptions using:
- volume of erupted material.
- height the ejected material reaches.
- duration in hours.
- qualitative measures (‘gentle’, ‘mega-colossal’).
What are earthquakes
The release of stress that has built up within the Earth’s crust caused by tension, compression or the shearing of rocks.
Release of energy causes seismic waves to be released from the focus.
Parts of an earthquake e.g focus, epicentre
Focus point at which waves originate from (point where stress is released).
Epicentre directly above the focus (where most severe impacts will be).
Seismic waves energy released travels as waves.
Fault line where movement in plates occur.
Where do earthquakes happen?
Mid-ocean ridge (divergent boundary)/rift valleys (constructive boundary)
Ocean trenches (convergent boundary)/island areas (destructive)
Collision zones (convergent)
Conservative margins (conservative)
Away from plate margins
Shallow focus earthquakes
0-70km deep
Occur in cold, brittle rock resulting from fracturing of rocks due to stress within the crust
Very common
Releasing low levels of energy
High-energy, shallow quakes are capable of causing severe damage
Deep focus earthquakes
70-700km deep
Increasing depth = extreme temps/pressures
Types of seismic waves
Primary (P) waves
Fast-travelling
Low-frequency
Compressional waves
Vibrate in the direction they’re travelling
Travel through Earth’s interior (through solids and liquids)
Secondary (S) waves
Half the speed of P waves
High-frequency
Vibrate at right angles to the direction they’re travelling
Cannot pass through liquids (so cannot travel through outer core)
Surface (L) waves
Slowest waves
Low-frequency
Rolling movements that move the surface vertically
Travel through outer crust only
Measuring earthquake magnitude
Richter scale
Measure of energy released on a logarithmic scale (each whole number represents a 10-fold increase in amplitude).
Largest record quakes are magnitude of around 9.
Doesn’t measure damage (partly determined by magnitude but also by population density and level of preparedness).
Modified Mercalli Scale (MMS)
Qualitative measure of damage experienced related to ground movement (impacts felt and seen by people).
Attempts to measure both intensity and impact.
Based on observation and description.
Moment magnitude scale (Mw)
Measures energy released more accurately than Richter.
Measures amount of movement of the ground - a direct function of energy.
Accurate for large earthquakes but not useful for smaller ones.
Describe the correlation between the Richter scale and MMI.
Suggest a reason for this
Positive correlation
Stronger earthquakes = more energy = more damage
Why is the Mw a more useful scale than the others?
Measures direct energy that causes ground movement so can be used to predict damage.
Effects of earthquakes on landforms and landscapes
Associated with formation of mountain ranges (e.g. Himilayas) at collision boundaries.
Collision of India and Eurasian plates led to complex pattern of folding and faulting of rocks creating the world’s highest fold mountains: 96/109 of world’s peaks >7000m located here.
Rift valleys along mid-ocean ridges (e.g. East Africa - evidence of earthquakes on morphology of Earth’s surface)
Fault scarps and escarpments of rift valleys mark locations of faults caused by tension and compression within crust.
Rift valleys are weathered and eroded so over time fault scarps are worn away and blend into landscape, can even disappear under accumulated sediments.
Hazards generated by earthquakes
Every year, around 100 earthquakes with potential to impact significantly.
2000-2015: estimated 800,000-900,000 killed by earthquakes.
Ground shaking and ground displacement
Local
Place specific
Potentially severe impacts?
Vertical and horizontal movement of ground.
Severity depends on:
- Earthquake magnitude
- Distance from epicentre
- Local geology
Close to epicentre of high-mag quakes with unconsolidated surface layers with high water content will experience extreme shaking.
Swaying of buildings impacts their stability
Displacement of rocks along fault lines can:
- Rip apart pipelines and sewers
- Sever rigid structures (railway tracks and roads)
- Cause building collapse
- Disrupt drainage systems (diverting streams and rivers, affecting movement of aquifers) - can have serious implications for public water supply and irrigation for agriculture.
Liquefaction
Vibrations of quake cause surface materials with high water contents (fine-grained sands, alluvium, landfill) to behave like liquids.
Materials loose strength; slopes (river banks) collapse and structures tilt and sink as foundations give way.
Landslides and avalanches
Place specific
Impact depends on geology
Shaking loosens lopes on mountains causing slope failure.
E.g. Himilayas - unstable/vulnerable (increased by deforestation and monsoon rains) even small tremors can cause landslides.
Nepalese quake (2015) triggered multiple landslides and avalanches caused by ground shaking.
- Block transport routes where accessibility is already difficult.
- Block rivers - natural dams create temporary lakes which lead to flooding when dam fails.
Tsunamis
Place specific
Coastal areas
Widespread
Regional/global
Underwater earthquakes
Cause sea bed uplift - displaces water above, producing powerful waves at surface which spread outwards from epicentre.
Wave height increases as they approach shoreline and shallower water.
Local height of wave affected by shape of sea bed and coastline.
Underwater landslides
When large volume of rock displaced underwater it slumps down, displacing water, creating a wave which radiates outwards.
CASE STUDY (Volcanoes)
MT ETNA, ITALY (AC)
MT MERAPI, INDONESIA (EDC)
Classifying volcanoes
Active: erupted within the last 10,000 years.
E.g. Kilauea (Hawaii) erupting continuously since 1983.
Dormant: has not erupted in last 10,000 years, expected to erupt some time in future.
E.g. Yellowstone erupted 70,000 years ago. There are ongoing earthquakes, geothermal features such as geysers and ground inflation).
Extinct: not expected to erupt ever again.
E.g. Kohala (Hawaii) erupted 120,000 years ago.
CASE STUDY (Earthquakes)
JAPAN, 2011 (AC)
Japan
Context
Location:
- Tohoku, Honshu Island, Japan, East Asia
- 70km offshore
- North part of main island
Tectonic context:
- Convergent (destructive) oceanic-continental plate boundary
- Pacific (oceanic) subducts beneath Eurasian (continental)
- 9.0Mw (BIG)
- Shallow focus earthquake (30km deep)
- 11th March, 2011
- Numerous aftershocks (7.0-8.0Mw)
Japan
Reasons why people choose to live here
Perception of risk
- Investment in education/engineering builds feeling of security.
- Experiences 400 earthquakes each day (most can’t be felt) - minor earthquakes help Japanese feel accustomed to these hazards.
Earthquakes and their effects are part of Japanese culture and folklore.
Small geo-thermal power plants since the 1960’s.
- There has been an attempt to increase the scale of operations especially in the wake of the Fukushima nuclear meltdown.
Intensive agricultural industry made possible by extremely fertile volcanic soils.
Volcanic activity has become a major tourist attraction in Japan.
Japan
Impacts experienced (2011)
Largest ever earthquake to hit Japan (9.0Mw).
Shaking lasted 3-7 minutes.
Many aftershocks.
7.0-8.0Mw
Tsunami waves created.
Reaching up to 40.5m tall (far higher than sea defences).
Travelled 10km inland (reaching the city of Sendai).
Waves reached Antarctica and USA.
Earthquake nocked out power supply to Fukushima Nuclear Power Plant.
Tsunami flooded back-up generators and triggered nuclear meltdown in three reactors.
400km stretch of coastline dropped 0.6m vertically.
Honshu island moves 2.4m east.
Japan
ECONOMIC impacts on country
Cost of the event estimated at nearly $181 billion.
45,700 buildings destroyed; 143,300 damaged.
15 ports damaged, 4 destroyed.
4.4. mullion households and thousands of businesses in northeast Japan were left without electricity.
Japanese stock market fell - major companies affected (Sony, Toyota, Panasonic) as power cuts halted production and port damage prevented export of goods.
Fishing industry affected as radioactive wast contaminates Pacific Ocean.
Farmland flooded by tsunami contained by salt - land made infertile.
Fukushima nuclear power plant had to be decommissioned after meltdown.
Japan
SOCIAL impacts on country
16,000 people were killed and 6,000 injured.
Bodies disposed of in mass graves to reduce the chance of disease.
Children separated from families (Save the Children reported 100,000 children affected).
2000 young people were either orphaned or lost 1 parent.
Extent of damage meant reconstruction of house, schools and health centres took 5 years.
5,800 people evacuated and permanently relocated from their family home after being evacuated from 30km fallout zone following Fukushima event.
Internal migration of people from Tokyo to Osaka in the months following the Fukushima event.
Japan
POLITICAL impacts on country
Government increased national debt to help recovery efforts; spent billions of yen to stabilise economy.
A large movement against nuclear power has developed and spread globally.
The government is yet to decide on the future of nuclear power.
International travel advice against visiting Japan (USA, France, Australia).
Foreign residents (e.g. international students) left the country.
Risk (R) = (HxV)/C
H - Frequency or magnitude of hazard
V - Level of vulnerability
C - Capacity of population to cope and adapt
(H)
Frequent hazards would increase risk because…
- People do not have time to recover from previous hazard (they’re still vulnerable).
- Regular disruption would limit economic/social development.
- Reduce investment in an area.
Stronger hazards would increase risk because…
- More energy causing more damage (more likely to be devastating).
- Less likely to mitigate successfully against unusually high magnitude hazards.
(V)
Vulnerability = whether people have to ability to withstand hazards.
More vulnerable people are at greater risk from hazards because small changes can have significant socio-economic impacts.
E.g. Subsistence farmers losing an area of crops are severely affected. Large landowner with same proportion of land affected would be less severely affected.
(C)
More resilient populations are at less risk because…
- Reduces damage done my hazard.
- Able to afford better mitigation strategies.
