Natural Hazards

  • Created by: rosie200
  • Created on: 14-03-17 16:47

Plate Tectonics

Divergent Plate

  • Two plates are forced apart by the convection currents in the mantle, magma then rises to fill the gap between the two places to form a volcano.
  • CS: Eyjafjallajokull, 2010 Iceland.
  • LANDFORMS: Volcanoes.

Convergent Plate

  • When oceanic and continental plates mov together. The Oceanic is forced under the continental plate, friction causes melting of the oceanic plate and triggers earthquakes.Magma rises up to the cracks and erupts the surface.
  • CS: Japan 2011
  • LANDFORMS: Earthquakes and Volcanos.
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Plate Tectonics

Collison Plate

  • Two continental plates collide, both forced up and form fold mountains.
  • CS: Himalayas 
  • LANDMARKS: Earthquakes and Fold Mountains

Conservative Plate

  • When two plates slide against each other in opposite directions but at different speeds. Friction is overcome and plates slip past in a sudden movement creating earthquakes.
  • CS: Haiti 2010
  • LANDFORMS: Earthquakes
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Plate Tectonics

Hot Spots Intra-Plate Earthquakes/Volcanos

  • Convection currents causes the heat to rise into plumes. The magma rises through the cracks in the crust surfaves which cools to form volcanoes.
  • CS: Hawaiian Islands
  • LANDFORMS: Volcanoes and Islands
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Shockwaves

SHOCKWAVES

  • Focus of an earthquake is where strain is released.
  • Primary waves arrive first and have a short wavelength and travel quickly through the crust, they shake the ground propagating. They expand material in same direction it travels.
  • Secondary waves arrive seconds later with a longer wavelength. They cause particles to oscillate and they can only travel through solids.
  • Surface waves move along the surface, arrive after the P and S waves.
  • Earthquake surface waves are divided into Love and Rayleigh.
  • Love waves have a particle motion and transverse to the direction of propagation. They have no vertical motion and side to side motion causes the ground to move like a snake=lot of damage. Transverse motion.
  • Rayleigh waves roll up and down. Have retrograde particle motion confined to verticle plane of motion.
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Wegners Theory

Wegners Theory

  • Wegners theory supports Continental Drift:
  • FOSSILS- Similar ones are found in other continents in similar climates.
  • GLACIERS- Not able to move as they were on land.
  • Rocks
  • Continets fit like a jigsaw [PANGEA]
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Intensity and Magnitude

Mercall:

  • Intensity
  • Arbitrary scale based on observation of damage.
  • Uses roman numerals up to 12.

Richter:

  • Magnitude
  • Recorded by a Seismograph.
  • Value in whole numbers and decimal fractions.
  • Each whole number increase shows 10 times amplitude.
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Tsunami

What causes a Tsunami?

  • A Tsunami is a large body of water that is caused by a sudden motion on the ocean floor which could be caused by: an Earthquake, Volcanic Eruption or Landslide.
  • Their Height can increase by several metres.
  • Waves slow down in shallow water and get cloer together.

What determines the impact of a tsunami?

  • Duration of event
  • Wave amplitude
  • Physical Geography of the coast, water depth and gradient.
  • Degree of coastal ecosystem buffer.
  • Timing of the event e.g. day or night.
  • Degree of coastal development 
  • Proximity from the coast,
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Japan Tsunami 2011 CASE STUDY

Japan 2011

  • 9.0 Magnitude earthquake.
  • 100 foot Tsunami.

IMPACTS:

  • 28,000 people dead and 465,000 people 'displaced'
  • Destroyed 120,000 buildings.
  • Fukushima power station damaged and the radiation contaminated the Pacific Ocean.
  • Nissan’ full year profits dropped 15% as result of shortages and production disruptions emanating from the disaster.
  • Global supply chain jobs were lost and communities were adversely affected.
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Japan Tsunami 2011 CASE STUDY

Japan Tsunami 2011

RESPONSE:

  • Operation USA began immediately working to address needs for material aid.
  • Staged disaster supplies were prepped and dispatched from OpUSA’s Port of Los Angeles warehouse—distributed through on the ground partner agencies in Japan.
  • first shipment of a $1.1 million donation of Gap brand winter clothing was distributed to tens of thousands of recipients in Miyagi, Fukushima and Iwate.

PREPAREDNESS:

  • The tsunami warning service sends signals from 180 seismic stations across Japan are monitored 24 hours a day by a computerized Earthquake and Tsunami Observation System.
  • Alerts on TVs
  • Built countless concrete breakwaters and floodgates to protect ports.
  • tightened building codes 
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Volcanic Hazards

PRIMARY:

  • Lava Flows- Molten rock that flows out of a volcano. Lava cannot be stoped or diverted.
  • Pyroclastic Density Currents- Polverized rock,ash and hot gases move at 100mph.Can be diluted as Pyroclastic surges or concetrated as in Pyrocladtic flows. Often from a collapse of lava dome.
  • Pyroclastic falls- Occurs when fragmented rock is ejected from a volcanic vent during an eruption and falls to the ground. Can block the sunlight which cools the earths surface.
  • Fumarole- Vent in the earths surface from which strem and colcanic gases are emitted

SECONDARY:.

  • Jokulhlaop- Glacial lake outburst flood where a dam containing a glacial lake fails perhaps due to lava melting the ice dam.
  • Lahars- Made up from a mud flow from volcanic debris, flows like a liquid and contains suspended materials.
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Volcanoes

PRIMARY HAZARDS:

  • Pyroclastic flows
  • Tephra 
  • Lava flows
  • Volcanic gases
  • Lahars 
  • Tsunamis

SECONDARY HAZARDS:

  • Soil Liquefaction
  • Landslides

SECONDARY IMPACTS:

  • Lahars
  • Jokulhlaups
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Haiti Earthquake 2010 CASE STUDY

Haiti Earthquake:

  • 7th January 2010
  • 7 Magnitude Earthquake
  • Slippage on the Conservative plate boundary

PRIMARY IMPACTS:

  • 220,000 people died
  • 300,000 people injured
  • 1.3 million homeless

SECONDARY IMPACTS:

  • Airport and Port damaged
  • Damage to main clothing industry
  • Cholrea outbreak

 

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Haiti Earthquake 2010 CASE STUDY

Haiti Earthquake 2010

PRIMARY RESPONSE:

  • Poor country, doesn't have the money or resources to redevelop
  • Dominican Republic provided emergency water and medical supplies.
  • Emergency rescue teams e.g. Iceland
  • United ntaion troops were distributed to give help and aid.

Secondary Response:

  • 1,300 people still in camps a year later.
  • Cash for work, are paying civillians to clear rubble.
  • Schools are being rebuilt.

PREPAREDNESS:

  • Few earthquake resistant buildings
  • Poor builidng regulations
  • Epicentre was near the centre
  • Few resources to help or aid the injured.
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Earthquakes Process

How do Earthquakes Occur?

  • Movements are preceded by a gradual build-up of tectonic strain, which stores elastic energy in crustal rocks.
  • When the pressure exceeds the strength of the fault,the rock fractures.
  • This produces a sudden release of energy, creating seismic waves that radiate away from the point of fracture.
  • The brittle crust rebounds either side of the fracture, which is the ground shaking, the earthquake felt on the surface.
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Understanding Risk

There is a complex relationship between risk, hazards and people:

  • Unpredictability-many hazards are not predictable
  • Lack of alternative-people may stay in hazardous zones due to lack of opitions e.g. work, lack of space to move or lack of skills or knowledge.
  • Dynamic hazards-the threat from haards is not a constant one and may not increase or decrease over time.
  • Russian Roulette- Optimism, turning a blind eye and hoping for the best.

The hazard rik formula capture the various components that influence the amount of risk that a hazard my produce for  community or population:

RISK= HAZARD X EXPOSURE X (VULNERABILITY/MANAGEABILITY)

DEGGS MODEL:

  • The more vulnerable the population, the higher the risk for disaster. [VENN DIAGRAM]
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Disaster Risk and Age Index

  • Ageing Populations
  • The accelaration of a risk in a world that is increasingly exposed to a range of hazard types.

Age is a significant factor in peoples resilience, with the elderly and children likely to suffer more from a hazard.

The index was developed by the UNISDR, to signal how age should be an important factor in understanding both vulnerbaility and the coping capacity of the older generation.

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The Pressure and Release Model

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Scales for different types of tectonic hazards

Richter Scale:Earthquake:0-9: A measurement of amplitude (height) of the waves produced by an earthquake.

Mercalli Scale:Earthquake: I-XII: Measures the experienced impacts of an earthquake. Based on key responses, movement of furniture and damage to structures.

Moment Magntiude Scale (MMS):Earthquake:0-9: A modern measure used by seismologists to describe earthquakes in terms of energy released.Based on the seismic moment of the earthquake, which is calculated from the amount of slip on the fault, the area affected and an Earth rigidity factor.

Volcanic Explosivity Index (VEI): Volcanic Eruption:0-8: A measure of the explosiveness of a volcanic eruption, which is calculated from the volume of products, height of the eruption cloud and qualitative observations.An increase of one index indicates an eruption that is ten times as powerful.

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Development, disaster impact and Vulnerability

There are several elements of development that relate to vulnerability and disaster risk:

  • An economic component dealing with the creation of wealth and the improvement of quality is equitably distributed.
  • social dimension in terms of health, education, housing and employment opportunities.
  • An environmental strand which has a duty of care for resource usage and distribution now and in the future.
  • political component including values such as human rights, politcal freedom and democracy.

Level of development and human activites that contribute towards disaster by increasing vulnerability+increasing new hazard risk. Development can also decrease risk.

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Tectonic mega-disasters and prediction

TECTONIC MEGA-DISASTERS

  • Usually large scale disasters on either an aerial or in terms of economic or human impact.
  • Pose serious problems for effective management to minimise the impact of the disaster

PREDICTION:PARKS MODEL

  • Stage 1: Modyfing the cause and event [pre-disaster]
  • Stage 2: Hazardous event [hours to weeks]
  • Stage 3: Search, rescue and care [hours to weeks]
  • Stage 4: Relief and Rehabilitation period, may include outside help [hours to weeks]
  • Stage 5: Nature of recovery related to: the need to reduce vulnerability and the need to restore normality as soon as possible. [weeks to years]
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Reducing impacts

Tsunami's impacts can be reduced by:

  • Mangroves, as they dissipate energy from waves whipped up by the wind 
  • Shore vegetation, as they can reduce the flow speed and height of an oncoming wave.
  • Dense coastal forest, as it will dissipate the energy from the waves.

Volcanoes impacts can be reduced by:

  • Seawater sprayed on the lava cools it down and therefore slows the movement down.
  • Satellites monitoring the temp and shape of the active volcano.
  • Sensors measure the levels of Co2 gas 
  • Seismometers record earthquakes as magma rises to fill gap.

Earthquakes impacts can be reduced by:

  • Hazard reistant buildings
  • Emergency plans
  • Evacuation routes
  • Earthquake drills.
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Benefits of living in hazardous areas

Benefits of living in a hazardous area-

  • Volcanoes produce fertile soils when the lava weathers
  • Many volcanoes have been dormant for years
  • Jobs provided in the tourist industry
  • Hot springs and baths e.g. Iceland
  • Heat produce electricity
  • Some people have the beliefs that the hazards won't happen to them.
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Modifying Vulnerability

Modifying vulnerability-

  • Prediction, forecasting and warnings.
  • Improvements in communities preparedness
  • Working with groups and individuals to change behaviours e.g. better land-use planning.
  • A tsunami warning system is used to detect tsunamis in advance and issue warnings to prevent loss of life and damage.
  • Land-use planning
  • Hazard resistant infastructure
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Modifying the loss

Modifying the loss-

Computer simulations are used to estimate the probability of damage from different earthquake events, based on:

  • Seismicity- how frequently earthquakes affect a particular location.
  • Seismic hazard- probability that a certain strength of shaking will occur.
  • Seismic risk- probability that a certain amount of risk will occur.
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Distribution of tectonic hazards

  • Global distribution of tectonic hazards is far from random.
  • Main earthquake zones are found along plate boundaries 
  • 70% of all earthquakes are found in the 'Ring of Fire' in the Pacific Ocean.
  • Most powerful earthquakes associated with convergent or conservative boundaries.
  • The oceanic fracture zone is a belt of activity through the ocean along the mid-ocean ridges, coming ashore in Africa, Red and Dead sea.
  • The continental fracture zone is a belt following the mountain ranges from Spain,via the Alps, the Himalayas and then circumscribing the Pacific.
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DEVELOPED EARTHQUAKE CASE STUDY

CASE STUDY: DEVELOPED EARTHQUAKE-JAPAN, KOBE

  • Earthquake hit at 5:46 AM on the 17th January 1995 on a Tuesday.

  • The earthquake lasted 20 seconds.

  • The epicentre was at the northern part of Awaji Island.

  • Measured 7.4 on the Richter scale.

  • Occurred as a result of plate movement along the boundary between the Philippines Plate, Pacific Plate and Eurasian Plate.

  • 6400 people dead and 35,000 people injured.

  • Buildings and bridges collapsed despite their earthquake proof design.

  • Buildings destroyed by fire when the gas mains fractured.

  • 316,000 people left homeless and refugees moved into temporary housing.

  • Many people moved away from the area permanently.

  • Jobs were created in the construction industry as part of a rebuilding programme.
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EMERGING TSUNAMI CASE STUDY

CASE STUDY: EMERGING TSUNAMI- INDIAN OCEAN

  • Occurred on 26th December 2004

  • It was the result of the Indio-Australian Plate sub ducting below the Eurasian Plate

  • Was caused by an earthquake that measured more than 9 on the magnitude

  • The earthquake caused the seafloor to uplift, displacing the seawater above

  • In open ocean the tsunami measured less than 1 metre high

  • The tsunami travelled at speeds up to 800km per hour.

  • When the Tsunami reached the shores, the height of the wave increased to 15 metres in some areas.

  • Quarter of a million people died.

  • Two million people were made homeless.

  • Short-term aid, such as water purification tablets, temporary housing and medical supplies were given from international countries.

  • Islands reliant on tourism and fishing, such as the Maldives, had to rebuild their industries.

  • An early warning system between countries surrounding the Indian Ocean has been set up.
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EMERGING EARTHQUAKE CASE STUDY

CASE STUDY: EMERGING EARTHQUAKE-INDIA, GUJARAT.

  • Both plates are continental (Collison plate boundary) , where both the plates are pushed up to form Fold Mountains. The Himalayas are the most obvious result of this collision. Along with the creation of Fold Mountains, the movement of the plates creates stress within the rocks. When the stress is suddenly released by rocks slipping past each other, we experience an earthquake.

  • Epicentre of the Gujarat earthquake was a small town called Bhuj.

  • Occurred at 08:46 local time, on Friday 26th January 2001.

  • 7.9 on the Richter scale.

  • 20,000 people confirmed as dead

  • 166,000 injured

  • 600,000 left homeless

  • 350,000 homes destroyed and another 844,000 damaged.

  • Cost of the earthquake was between $1 and $5 billion.

  • Water table rose to surface level.

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DEVELOPING VOLCANO CASE STUDY

CASE STUDY: DEVELOPING VOLCANO- NYIRAGONGO and SHIELD VOLCANO

  • Occurred on the 17th January 2002

  • Disturbed by the movement of plates along the East African Rift Valley

  • Led to lava spilling southwards in three streams

  • The lava flowed across the runway at Goma airport and through the town splitting it in half

  • Lava destroyed many homes as well as roads and water pipes, set off explosions in fuel stores and power plants and killed 45 people.

  • Nyiragongo is part of the East African Rift Valley. This is an area of many faults where the plates are being stretched as they move away from each other.

  • The unrest in the country has made it difficult to monitor the volcano and put emergency responses in place.

  • 45 people died in the first 24 hours.

  • The lava flow made it difficult to travel around Goma as it filled the roads. Aid agencies were unable to access some areas of Goma.

  • The lava took a long time to cool and it burnt people as they tried to return to their homes.

  • Cholera spread because of lack of sanitation in areas that people fled to.

  • Around 50 people were killed when fuel exploded while they were trying to siphon it off at a petrol station.

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EMERGING VOLCANO CASE STUDY

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DEVELOPED VOLCANO CASE STUDY

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DEVELOPING TSUNAMI CASE STUDY

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