Edexcel Geography A-level Tectonic Processes and Hazards Flashcards

The Global Distribution of Hazards

• A hazard is a potential threat to human life and property.

• A natural hazard can be either hydro-meteorological (caused by climatic processes) or geophysical (caused by land processes).

• Geophysical hazards occur near plate boundaries due to varying speeds and directions of plate movement, leading to collisions, earthquakes, and volcanic activity.

• Earthquakes can also occur near the middle of plates (intra-plate) due to pre-existing weaknesses in the plates that become reactivated.

• Volcanic hotspots, like the Ring of Fire, are situated amongst the center of plates due to localized areas of high temperature in the lithosphere from upwelling of hot molten material from the core.

• Magma rises as plume (hot rock) at hotspots, such as the Hawaii hotspot.

• The most powerful earthquakes usually occur at convergent or conservative boundaries.

• OFZ (Oceanic Fracture Zone) - Belt of activity through the oceans and along mid-ocean ridges.

• CFZ (Continental Fracture Zone) - Belt of activity along mountain ranges.

Tectonics Trends since 1960

• The total number of recorded hazards has increased.

• The number of fatalities has decreased, but there are spikes during mega-disasters.

• The total number of people affected by tectonic hazards is increasing due to population growth.

• The economic costs associated with hazards and disasters have increased significantly, partly due to increases in development and insurance policies.

• Reporting disaster impacts is difficult and controversial due to:

  • Distinction between direct and indirect deaths.

  • Challenges in collecting data from rural, isolated, or densely populated areas.

  • Different methods used by different organizations leading to varying statistics.

  • Potential bias in death tolls reported by governments.

Tectonic Theory: Characteristics of the Earth’s Structure

• Earth consists of four sections:

  • Crust (Lithosphere): Uppermost, thinnest, least dense layer. Oceanic crust is 7km thick, continental crust up to 70km thick.

  • Mantle (Asthenosphere): Composed of silicate rocks rich in iron and magnesium. Semi-molten with convection currents due to a temperature gradient, contributing to plate tectonic movement. Located 700km to 2890km below the crust.

  • Outer Core: Dense, semi-molten rocks containing iron and nickel alloys. Located 2890km to 5150km below the Earth’s surface.

  • Inner Core: Similar composition to the outer core, solid due to extreme pressures. Located over 5150km below the Earth’s crust.

• The core’s high temperature is a result of:

  • Primordial heat left over from the earth’s formation

  • Radiogenic heat produced from radioactive decay

Plate Boundaries

• Different plates can move towards each other (destructive plate margin), away from each other (constructive plate margin), or parallel to each other (conservative plate margin).

• Different landforms are created in these different interactions.

Destructive Plate Boundaries

• Continental and Oceanic:

  • Denser oceanic plate subducts below the continental plate.

  • The plate subducting leaves a deep ocean trench.

  • The oceanic crust is melted as it subducts into the asthenosphere.

  • The extra magma created causes pressure to build up.

  • Pressurized magma forces through weak areas in the continental plate.

  • Explosive, high-pressure volcanoes erupt through the continental plate, known as composite volcanoes.

  • Fold mountains occur when sediment is pushed upwards during subduction.

• Oceanic and Oceanic:

  • Heavier plate subducts leaving an ocean trench. Fold mountains will also occur.

  • Built up pressure causes underwater volcanoes bursting through the oceanic plate.

  • Lava cools and creates new land called island arcs.

• Continental and Continental:

  • Both plates are not as dense as oceanic so lots of pressure builds.

  • Ancient oceanic crust is subducted slightly, but there is no subduction of continental crust.

  • Pile up of continental crust on top of the lithosphere due to pressure between plates.

  • Fold mountains formed from piles of continental crust.

Constructive Plate Boundaries

• Oceanic and Oceanic:

  • Magma rises in between the gap left by the two plates separating, forming new land when it cools.

  • Less explosive underwater volcanoes formed as magma rises.

  • New land forming on the ocean floor by lava filling the gaps is known as sea floor spreading.

  • Paleomagnetism is the study of rocks that show the magnetic fields of the Earth. As new rock is formed and cools the magnetic grains within the rock align with the magnetic poles.

  • Geologists observed that there are symmetrical bands of rock with alternating bands of magnetic polarity either side of constructive plate boundaries. This is evidence of seafloor spreading.

• Continental to Continental:

  • Any land in the middle of the separation is forced apart, causing a rift valley.

  • Volcanoes form where the magma rises.

  • Eventually the gap will most likely fill with water and separate completely from the main island.

  • The lifted areas of rocks are known as horsts whereas the valley itself is known as a graben.

• Ridge push: The slope created when plates move apart has gravity acting upon it as it is at a higher elevation. Gravity pushes the plates further away, widening the gap (as this movement is influenced by gravity, it is known as gravitational sliding).

• Slap pull: When a plate subducts, the plate sinking into the mantle pulls the rest of the plate (slab) with it, causing further subduction.

Conservative Plate Boundary

• Between any crust, the parallel plates move in different directions or at different speeds.

• No plates are destroyed so no landforms are created.

• When these plates move, a lot of pressure is built up.

• On oceanic crust, this movement can displace a lot of water.

• On continental crust, fault lines can occur where the ground is cracked by the movement.

Plate Movements

• Oceanic crust:

  • High density of rock, mainly basalt, thin, newly created.

• Continental crust:

  • Low density of rock, mainly granite, thick, old.

• Mantle Convection - Radioactive elements in the core of the Earth decay which produce a lot of thermal energy. This causes the lower mantle to heat up and rise, as the magma rises it cools down and becomes more dense and begins to sink back down to the core. These are convection currents. These convection currents push the plates.

• Slap Pull - Old oceanic crust (which is the most dense plate) will submerge into the mantle. This pulling action drags the rest of the plate with it.

• Slab Pull is the primary mechanism for plate movement; convection currents seem too weak to move massively dense plates.

Earthquakes

• Plates do not perfectly fit into each other, meaning they do not move in fluid motions. At all boundaries, plates can become stuck due to the friction between plates.

• When the plates are stuck, the convection currents in the asthenosphere continue to push, which builds the pressure. It builds so much that it cannot be sustained and the plates eventually give way.

• All of this pressure is released in a sudden movement, causing a jolting motion in the plates. This jolt is responsible for seismic movement spreading throughout the ground in the form of seismic waves (or shock waves).

• The focus (or hypocenter) is the point underground where the earthquake originates from.

• The epicenter is the area above ground that is directly above the focus.

Seismic Waves

• Primary

  • Travels through solids

  • Compressional

  • Vibrates in the direction of travel

  • Travels at 4-8 km/s

• Secondary

  • Vibrate at right angles to direction of travel

  • Travels only through solid rocks

  • Travels at 2.5 - 4 km/hr

• Love

  • Near to ground surface

  • Rolling motion producing vertical ground movement

  • Travels at 2-6 km/hr

• Rayleigh

  • Vertical and horizontal displacement

  • Travels at 1-5 km/hr

  • Compressional

• Secondary and Love waves are the most destructive as they have large amplitudes.

• Due to their different speeds, these different waves will hit a location at different times.

• Intensity of waves will decrease further from the epicenter, as waves lose energy as they travel.

Secondary Hazards of Earthquakes

• Soil Liquefaction

  • Affects poorly compacted sand and silt.

  • Water moisture within the soil separates from the soil particles and rises to the surface.

  • This can cause the soil to behave like a liquid, which can cause building subsidence or landslides.

• Landslides

  • The shaking caused by the earthquake can weaken or damage cliff faces, hills, and snow material.

  • Unconsolidated material or loose rocks can collapse.

  • Landslides can travel several miles and accumulate material on the way.

  • Risk varies with topography rainfall, soil, and land use.

• Tsunamis

  • When an oceanic crust is jolted during an earthquake, all of the water above this plate is displaced, normally upwards

  • This water is then pulled back down due to gravity. The energy is transferred into the water and travels through it like a wave.

  • The water travels fast but with a low amplitude (height).

  • As it gets closer to the coast, the sea level decreases so there is friction between the sea bed and the waves.

  • This causes the waves to slow down and gain height, creating a wall of water that is on average 10 feet high but can reach 100 feet.

• Tsunamis are generally generated in subduction zones at convergent plate margins.

• Most tsunamis are found along the Pacific ring of fire, hence the most vulnerable countries are often located in Asia or Oceania.

• The impact of a tsunami depends on various human and physical factors:

  • Population density of area hit

  • Coastal defenses

  • Duration of the event

  • Wave amplitude and distance traveled

  • Gradient of the continental shelf

  • The shape of the land - bays will funnel and concentrate tsunami waves.

  • Warning & Evacuation Systems

  • Level of economic and human development

Volcanoes

• Primary hazards, caused directly from the volcano, tend to have a fast speed of onset:

  • Lava flows: Streams of lava that have erupted onto the Earth’s surface. Fast-flowing lava can be very dangerous which depends on the lava's viscosity.

  • Pyroclastic flows: Mixture of hot dense rock, lava, ash, and gases which move very quickly along the surface of the Earth. They can cause asphyxiation.

  • Tephra and ash flows: Pieces of volcanic rock and ash are blasted into the air. This can cause serious damage to buildings.

  • Volcanic gases: Gases like sulfur dioxide and carbon monoxide are released into the atmosphere.

• Secondary hazards occur as a result of the heat produced by the volcano:

  • Lahars: Combination of rock, mud, and water which travel quickly down the sides of volcanoes.

  • Jokulhaup: Snow and ice in glaciers melt after an eruption which causes sudden floods.

  • Acid rain: Caused when gases such as sulfur dioxide are released into the atmosphere.

Classification and Theories of Tectonic Events

• Disaster: A serious disruption of the functioning of a community or society involving human, material, economic, and environmental losses which exceeds the ability of the affected community or society to cope using its own resources.

• The risk a community faces from a natural hazard can be calculated from the equation below.

• How developed a country is significantly affects how resilient its population is and its capacity to cope with a hazard.

• A place may be at high risk if:

  • Their capacity to cope is low.

  • They are quite vulnerable.

  • The hazard is large/ high intensity.

• Degg's Model: A disaster will only occur when a vulnerable population is exposed to a hazard. If the population is not vulnerable, the hazard will not have a significant effect, thus the event will not be disastrous.

• Different organizations will define a hazard and disaster differently, based on their interests and what they believe is most important.

• There are other ways to classify a tectonic hazard, each measure having different successes and downfalls in correctly representing the magnitude and impact of a disaster:

  • The volume of people affected - The International Disaster Database classifies a disaster as an event where more than 100 people are affected or more than 10 people die.

  • Economic cost of the disaster - jobs lost, cost of repairs needed, economic productivity lost. The UN Sendai Framework is an initiative to reduce economic loss due to a disaster, after the huge economic losses during the 2011 Tohoku Earthquake & Tsunami.

  • You could compare a tectonic disaster to previous events, prediction models or average statistics for that location. Some events may be more severe than the ‘average’ tectonic hazard, due to a series of factors coinciding (e.g. bad weather and recent deforestation will increase the tsunami traveling inland).

• It is important to treat average statistics carefully - rare mega-disasters could skew the statistics. For example, if you take 100 tectonic events for Iceland - 99 events cause 3 fatalities and 1 event causes 10,000 fatalities (not real data!) - would the average fatality of 103 people be representative of all tectonic events that occur in Iceland?

The Park Model

• The Park Model is a graphical representation of human responses to hazards. The model shows the steps carried out in the recovery after a hazard, giving a rough indication of time frame.

  • The steepness of the curve shows how quickly an area deteriorates and recovers.

  • The depth of the curve shows the scale of the disaster (i.e. lower the curve, lower the quality of life).

The Park Model of Human Response to Hazards

• Stage 1 - Relief (hours-days)

  • Immediate local response - medical aid, search and rescue

  • Immediate appeal for foreign aid - the beginnings of global response

• Stage 2 - Rehabilitation (days-weeks)

  • Services begin to be restored

  • Temporary shelters and hospitals set up

  • Food and water distributed

  • Coordinated foreign aid - peacekeeping forces etc.

• Stage 3 - Reconstruction (weeks-years)

  • Restoring the area to the same or better quality of life

  • Area back to normal - ecosystem restored, crops regrown

  • Infrastructure rebuilt

  • Mitigation efforts for future event

• The model also works as a control line to compare hazards. An event that is catastrophic would have a steeper curve than the average and would need more time to recover.

The Pressure and Release Model (PAR)

• The Pressure and Release Model is used to analyze factors which cause a population to be vulnerable to a hazard. On one side of the model we have the natural hazard itself, and on the other side different factors and processes which increase a population’s vulnerability to the hazard. This vulnerability is often rooted in social processes. These are dynamic and ever-changing and are often unrelated to the hazard itself e.g., poverty, poor governance.

• The PAR model is complex; no two hazards are the same and factors leading to vulnerability are interconnected and hard to measure. If we reduce the social factors affecting a population, we can reduce the pressure they face and so reduce their vulnerability and the effect of natural hazards.

• The progression of vulnerability is split into three sections. The root causes are often caused by economic, demographic, and/or political processes, often affecting large populations or entire countries. Dynamic pressures are local economic or political factors, that can affect a community or organization and unsafe conditions are the physical conditions that affect an individual (unsafe building, low income, poor health, etc.).

• Therefore, the number of people affected will increase the closer the factor is to the root cause.

• Vulnerability can be defined differently, depending on who or what is affected:

  • Physical Vulnerability - Individuals live in a hazard-prone area, with little protection naturally or through mitigation.

  • Economic Vulnerability - People risk losing their employment, wealth, or assets during a hazard. MEDCs tend to be more economically vulnerable than LEDCs.

  • Social Vulnerability - Communities are unable to support their disadvantaged or most vulnerable, leaving them at risk to hazards.

  • Knowledge Vulnerability - Individuals lack training or warning to know the risks of a hazard or how to safely evacuate. Alternatively, religion and beliefs may limit their understanding of hazards; hazards are an act of God, so individuals don’t mitigate or evacuate (known as fatalist belief).

  • Environmental Vulnerability - A community’s risk to a hazard is increased due to high population density in the area.

• The Pressure & Release Model suggests that a series of factors leads to a population’s vulnerability. For example:

  • A lack of infrastructure (such as poor sewage management or water supplies) can worsen the impacts of a hazard, since it is harder to maintain clean living conditions and avoid the spread of disease following a disaster. A lack of infrastructure would be a factor of unsafe living conditions.

  • However, the lack of infrastructure may be due to rapid urbanization, where little planning has been taken to carefully construct houses and infrastructure to cope with the rising population; Rapid urbanization would be the dynamic pressure.

  • Ultimately, planning and controlling safe population growth is the government’s responsibility. So the root cause of this disaster may be weak governance.

Common factors that affect the vulnerability of a society

• Root Cause:

  • Weak Governance

  • Mismanagement by Industry, NGOs, or IGOs

  • High reliance on products easily affected by hazards (local agriculture near to the hazard, imports by air during a volcanic eruption)

• Dynamic Pressures:

  • lack of training/knowledge in locals.

  • rapid urbanization

  • poor communication between government and locals

  • natural environment

• Unsafe Living Conditions:

  • lack of infrastructure (clean water, sewage removal, electricity)

  • dangerous location of settlements (close to nuclear stations or the natural hazard itself)

  • no warning system for locals

  • degraded (mangroves removed, rivers & channels filled with debris)

  • lack of basic services (health, education, police)

  • disease and fire can easily spread between households

Tectonic Hazard Profiles

• A hazard profile compares the physical characteristics which all hazards share. Hazard Profiles can help decision-makers when deciding where to allocate the most human and financial resources.

• It is easy to measure a single hazard like earthquakes but it is much more difficult to measure multiple hazards or events where secondary hazards are more destructive than the actual event itself.

The characteristics of a hazard profile included:

• Frequency – How often it happens

• Magnitude – How extensive an area the event could affect

• Duration – How long the event lasts

• Speed of onset – How much warning time before the event occurs

• Fatalities - Number of deaths caused

• Economic Loss - Value of assets damaged, lack of industry or economic productivity, insurance policies.

• Spatial Predictability - The predictability of where would be affected.

• Evaluating the Effectiveness of Models

• Hazard models are useful, but the unpredictability of hazards makes the models less effective at accurately representing human responses to hazards.

Evaluation Questions

• Can they be applied to every hazard? Are some hazards more complicated and require a more complex model? It may be useful to apply each of your case studies to these models and see how they compare.

• Does the model take any aspects of hazards into account such as level of development?

• Is there any timeframe? Do the models accurately lay out the time taken for a full response and how this changes due to aspects of the hazard such as intensity?

• Could the model be less vague/ include more steps that can be applied to all hazards?

• Does the model present hazards currently? Are there any alterations that could be made to account for hazards affected by climate change? Will the model eventually not represent human responses at the time (e.g., could the cycle stop because hazards will occur more frequently than the mitigation strategies will occur)?

Measuring Tectonic Events

Volcanic Explosivity Index (VEI)

• Measures the relative explosiveness of a volcanic eruption.

• Based on the height of ejected material and duration of eruption.

• Scale goes from 0-8 and is logarithmic (increase of 1 on the scale indicated a 10 times more powerful eruption).

The Modified Mercalli Scale

• Measures the destructiveness of an earthquake.

• It is a relative scale as people would feel different amounts of shaking in different places.

• It is subjective as based on if people wake up, if furniture moves, how much damaged structures receive.

• The scale varies from I to XII

• I = Generally not felt by detected on seismographs

• XII = Nearly total destruction

• It doesn’t consider economic, social, and environmental impacts.

Moment Magnitude Scale

• Measures the amount of energy released in the earthquake.

• Scale from 0-9.

• It's a simple measure, so environmental or social impacts must be inferred.

Richter Scale

• Measures the amplitude of the waves produces during an earthquake

• Most widely used scale, as it's absolute

• Must infer social or environmental impacts, which can be misleading. The highest Richter scale earthquake readings won't necessarily be the worst disasters.

• Like the VEI its scale is logarithmic.

Managing Tectonic Hazards

• Hazards can be responded to by preventing them directly, being prepared for the next hazard, mitigating the effects, or completely adapting your lifestyle to limit the hazard’s effects.

The Hazard Management Cycle

• The Hazard Management Cycle outlines the stages of responding to events, showing how the same stages take place after every hazard.

Stages

• Preparedness: Being ready for an event to occur (public awareness, education, training)

• Response: Immediate action taken after event (evacuation, medical assistance, rescue)

• Recovery: Long-term responses (restoring services, reconstruction).

• Mitigation: Strategies to lessen effects of another hazard (barriers, warning signals developed, observatories).

Monitoring and Prediction

• It is not possible for us to predict accurately when an earthquake will happen; instead, the risk of an earthquake can be forecast based on a statistical likelihood. Forecasts can be based on data and evidence gathered through global seismic monitoring networks and also from historical records.

• Scientists can sometimes predict volcanic eruptions with some degree of accuracy. Scientists can use special equipment to monitor volcanoes and detect signs of imminent eruption:

  • Small earthquakes - called tremors

  • Changes to the top surface of the volcano as it swells when magma builds up

  • Changes to the tilt as the slope angle changes when magma builds up

Approaches

• Mitigation: Identifies the characteristics of the potential hazard and what can be done to reduce their impact on people, such as:

  • Land use zoning

  • Building codes and regulation

  • Protective defenses (tsunami wall)

• Preparedness: Minimizing loss of life and property

  • Developing preparation plans

  • Developing warning systems

  • Stockpiling medicines, food, water etc.

  • Education, training, drill

• Response: Coping with a disaster, the main aims would be to rescue people and reduce economic losses:

  • Search and rescue efforts

  • Evacuating people

  • Restoring vital infrastructure like water and electricity

  • Restoring vital services like law enforcement and health care

• Local Aid and International Aid: Focuses on short-term and long-term recovery

Short-term:

• Providing aid, food, water, shelter

• Providing financial assistance so people can rebuild their livelihoods

Long term:

• Rebuilding homes

• Building and repairing infrastructure

• Reopening schools and businesses

Management Approaches

• There are three different approaches to managing a tectonic hazard and reducing their impact: Modify the Event, Modify the Vulnerability, Modify the Loss.

Modify the Event

• We cannot control seismic activity. However, we can control the design of buildings.

Micro

* Strengthening individual buildings and structures

Macro

* Large scale support and protective measures designed to protect whole communities

Strategies:

For Earthquake:
* Mainly micro approach
* Emphasis is put into public buildings like hospitals, police stations and other vital infrastructure
* Schools and factories are strengthened to help shelter people
* Some improvements to private houses
For Tsunamis:
* Tsunami walls work for a given amplitude and threshold of wave
* Replanting coasts with mangroves and coastal forestry dissipates energy from waves
For Volcanoes:
* Diverting flows of lava
* Reinforcing house roofs to withstand large deposits of ash

Modification Types:

Land use zoning

• Preventing building on low-lying areas and areas of high risk. Low cost. Reduces vulnerability. Stops economic development on some high-value land. Strict enforcement required.

Resistant buildings

• Buildings with deep foundations, sloped roofs so that ash doesn’t build up and create pressure can help prevent collapsing. Protects people and property. High cost for larger buildings. Low-income families cannot afford this.

Tsunami defenses

• Sea walls which stop waves traveling inland reduces damage. Provides security. Very high cost. Doesn’t look nice. Can be overtopped.

Lava diversion

• Barriers and water cooling to divert and slow down lava flowdiverts lava away, low cost. Only works for low VEI lava

Modify the Vulnerability

Hi Tech Scientific Monitoring

• Monitors volcano behavior and predict eruptions. Predicting eruption is possible in some cases, warning and evacuation can help save lives. Costly. In LDCs, volcanoes aren’t usually monitored. Doesn’t prevent property damage.

Community Preparedness and Education

• Low cost and often implemented by NGOs. Can save lives through small actions, doesn’t prevent property damage, harder to implement in isolated rural areas.

Adaptation

• Moving out of harm’s way and relocationhelps save lives and property, high population densities prevent it, disrupts people’s traditional home and traditions.

Modify the Loss

Short term aid

• Search and rescue and also food, water, aid, and shelter can help reduce the death toll by saving lives and keeping people alive until long-term aid is provided. High costs and technical difficulties in isolated areas. Emergency services are limited and are poorly equipped in LDCs.

Long term aid

• Reconstructions plants to rebuild an area and improve resilience. Reconstruction can help improve resilience through land use planning and better construction methods. Very high costs. Needs are quickly forgotten by the media shortly after the disaster.

Insurance

• Compensation to replace losses, which allows people to recover economically for paying reconstruction. Doesn’t help save lives, and not many in LDCs have insurance.

Community Role

• In remote and isolated areas, it may take a long time for aid to come, and people may begin local recovery operations; communities may clear debris from roads and set up temporary shelters.

NGOs & TNCs Role

• NGOs play a very important role from providing funds, coordinating rescue efforts, and helping to develop reconstruction plans. Occasionally, TNCs and NGOs may cooperate; Charity buckets or events may be organized by businesses to improve IGOs' ability to help.

Development and Governance

• Governments of developing countries may not prioritize investing money in hazard mitigation as they tend to focus their resources on development and economic growth. This lack of investment in hazard management often means that less developed countries and their populations are more vulnerable to hazards.

• The Risk Poverty Nexus states that poverty is both a contributing factor and consequence of a natural hazard. It suggests that a positive feedback mechanism can cause further economic loss for already poor countries.

• Low-income households and communities are generally more affected by impacts and losses. There are various types of inequalities, each affecting a community’s resilience to a hazard:

  • Asset inequality relates to housing and security of tenure and also agricultural productivity.

  • Political inequality where certain groups of people, usually the wealthy and elite, hold quite a lot of power and political influence.

  • Social status inequality often directly linked to space and has a bearing on other dimensions of inequality, including the ability of individuals and groups to secure regular income and access services.

  • Entitlement inequality refers to unequal access to public services and welfare systems as well as inequalities in the application of the rule of law.

Hazard Vulnerability

There are many factors that can contribute to a population’s vulnerability:

Unstable political governance and/or corruption

• A lack of political cohesion can impact on how prepared a country is for a hazard and can also negatively impact response and recovery efforts after the event.

Population density

• The higher the population density the more people are affected by a hazard.

Geography isolation and accessibility

• Remote, rural areas often have poor transport links which can negatively affect rescue efforts.

Level of urbanization

• Urban areas tend to be worse affected by hazards due to two factors: urban areas are densely populated (see above) and also have larger amounts of infrastructure meaning there is more economic damage.

Governance

Meeting basic needs

• When food supply, water supply, and health needs are met, the population is generally less vulnerable to secondary hazards such as diseases.

Planning

• Land-use planning can reduce risk by preventing people living in areas of high risk. Secondary hazards may be made worse by deforestation.

Preparedness

• Education and community preparation programs raise awareness and teach people how to prepare, evacuate and act when a disaster strikes.

Corruption

• If government politicians accept bribes and do unethical things, then vulnerability would increase as money would be invested in crucial areas like emergency services

Tectonic Mega-Disasters

Characteristics:

• Large-scale disaster affecting large spatial areas or large population.

• They pose problems in effective management to minimize the impacts.

• The scale of the impact may require international support and aid.

• Mega Disasters are low probability (rare).

• The globalization of production and supply chains has allowed international businesses to reduce costs and become more efficient. However, mega-disasters significantly damage globalized businesses.

Business disruption examples:

• 2011 Tohoku earthquake & tsunami

  • There was a knock-on effect for TNCs such as Toyota and BMW which operate and source products from Japan. This lost potential revenue for those TNCs and caused general economic uncertainty.

• 2011 Eyjafjallajökull eruption

  • The significant ash cloud closed European airspace, which led to the halt of goods and trade into the EU by air. This resulted in Kenyan flowers (to be imported into the EU) couldn't be transported and wilted.

EQ1: Why are some locations more at risk from tectonic hazards?

• A hazard is a potential threat to human life and property.

• A natural hazard can be either hydro-meteorological (caused by climatic processes) or geophysical (caused by land processes).

• Geophysical hazards occur near plate boundaries due to varying speeds and directions of plate movement, leading to collisions, earthquakes, and volcanic activity.

• Earthquakes can also occur near the middle of plates (intra-plate) due to pre-existing weaknesses in the plates that become reactivated.

• Volcanic hotspots, like the Ring of Fire, are situated amongst the center of plates due to localized areas of high temperature in the lithosphere from upwelling of hot molten material from the core.

• Magma rises as plume (hot rock) at hotspots, such as the Hawaii hotspot.

• The most powerful earthquakes usually occur at convergent or conservative boundaries.

• OFZ (Oceanic Fracture Zone) - Belt of activity through the oceans and along mid-ocean ridges.

• CFZ (Continental Fracture Zone) - Belt of activity along mountain ranges.

• Different plates can move towards each other (destructive plate margin), away from each other (constructive plate margin), or parallel to each other (conservative plate margin).

• Plates do not perfectly fit into each other, meaning they do not move in fluid motions. At all boundaries, plates can become stuck due to the friction between plates.

• When the plates are stuck, the convection currents in the asthenosphere continue to push, which builds the pressure. It builds so much that it cannot be sustained and the plates eventually give way.

• Tsunamis are generally generated in subduction zones at convergent plate margins.

• Most tsunamis are found along the Pacific ring of fire, hence the most vulnerable countries are often located in Asia or Oceania.

EQ2: Why do some hazards develop into disasters?

• The total number of recorded hazards has increased.

• The number of fatalities has decreased, but there are spikes during mega-disasters.

• The total number of people affected by tectonic hazards is increasing due to population growth.

• The economic costs associated with hazards and disasters have increased significantly, partly due to increases in development and insurance policies.

• Reporting disaster impacts is difficult and controversial due to:-

  • Distinction between direct and indirect deaths.

  • Challenges in collecting data from rural, isolated, or densely populated areas.

  • Different methods used by different organizations leading to varying statistics.

  • Potential bias in death tolls reported by governments.

• Disaster: A serious disruption of the functioning of a community or society involving human, material, economic, and environmental losses which exceeds the ability of the affected community or society to cope using its own resources.

• The risk a community faces from a natural hazard can be calculated from the equation below.

• A place may be at high risk if:-

  • Their capacity to cope is low.

  • They are quite vulnerable.

  • The hazard is large/ high intensity.

• Degg's Model: A disaster will only occur when a vulnerable population is exposed to a hazard. If the population is not vulnerable, the hazard will not have a significant effect, thus the event will not be disastrous.

• The Pressure and Release Model is used to analyze factors which cause a population to be vulnerable to a hazard. On one side of the model we have the natural hazard itself, and on the other side different factors and processes which increase a population’s vulnerability to the hazard. This vulnerability is often rooted in social processes. These are dynamic and ever-changing and are often unrelated to the hazard itself e.g., poverty, poor governance.

• The Pressure & Release Model suggests that a series of factors leads to a population’s vulnerability. For example:-

  • A lack of infrastructure (such as poor sewage management or water supplies) can worsen the impacts of a hazard, since it is harder to maintain clean living conditions and avoid the spread of disease following a disaster. A lack of infrastructure would be a factor of unsafe living conditions.

  • However, the lack of infrastructure may be due to rapid urbanization, where little planning has been taken to carefully construct houses and infrastructure to cope with the rising population; Rapid urbanization would be the dynamic pressure.

  • Ultimately, planning and controlling safe population growth is the government’s responsibility. So the root cause of this disaster may be weak governance.

• The Risk Poverty Nexus states that poverty is both a contributing factor and consequence of a natural hazard. It suggests that a positive feedback mechanism can cause further economic loss for already poor countries.

• There are many factors that can contribute to a population’s vulnerability:-

  • Unstable political governance and/or corruption

  • Population density

  • Geography isolation and accessibility

  • Level of urbanization

EQ3: How successful is the management of tectonic hazards and disasters?

• Hazards can be responded to by preventing them directly, being prepared for the next hazard, mitigating the effects, or completely adapting your lifestyle to limit the hazard’s effects.

• Modified Mercalli Scale- Measures the destructiveness of an earthquake.

• Moment Magnitude Scale- Measures the amount of energy released in the earthquake.

• Scientists can sometimes predict volcanic eruptions with some degree of accuracy. Scientists can use special equipment to monitor volcanoes and detect signs of imminent eruption:-

  • Small earthquakes - called tremors

  • Changes to the top surface of the volcano as it swells when magma builds up

  • Changes to the tilt as the slope angle changes when magma builds up

• There are three different approaches to managing a tectonic hazard and reducing their impact: Modify the Event, Modify the Vulnerability, Modify the Loss.

• The Hazard Management Cycle outlines the stages of responding to events, showing how the same stages take place after every hazard.

• Hazard Profiles can help decision-makers when deciding where to allocate the most human and financial resources.

• The Parks Model is a graphical representation of human responses to hazards. The model shows the steps carried out