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What is a hazard


A hazard is a potential threat to human life and property

A natural hazard can be either hydro-meteorological (Caused by Climate processes of Geophysical (Caused by Land processes)

Geophysical hazards occur near plate boundaries. These plates move at different speeds and directions which can cause collisions, earthquakes and volcanic activity.


What can the earths crust be divided into

  • The earths structure can be divided into four sections: Inner core, outer
    core, mantle and the crust
  • The earth’s crust then can then further divided into a series of plates: Oceanic (Thin and very dense) or Continental (thick and less dense)

Explain the three differences between plate boundaries

  • Conservative – plates move past each other but at different speeds, causing
    friction and collisions
  • Constructive – plates moving apart from one another, most clearly displayed
    at ocean ridges
  • Destructive - plates move towards each other, colliding head on if both are
    continental. If one is oceanic and the other oceanic, subduction will occur
    where the oceanic plate is thrust under the continental plate as it is denser.
    If there are two oceanic plates the heavier plate will be forced under the

Explain Plate Tectonic Theory


Plate Tectonic Theory is believed to be correct due to evidence from Wegner’s Continental Drift Theory which states that the shapes of South Africa seem to fit together so they were once part of a supercontinent. This is supported by similar rock types and fossils found on the east coast of South America and west coast of Africa.


What is a mid ocean ridge


An underwater mountain range, formed by the process of subduction where oceanic plates are pushed under continental as oceanic plates are heavier.


What is sea floor spreading


New crust rides formed when two oceanic plates move away from each other, allowing magma from the mantle to rise


What is Palaeomagnetism and explain the significance of


Palaeomagnetism is the magnetic patterns of cooled magma. A study of this phenomenon discovered that magnetic patters were arranged in the direction of the earth’s magnetic field which flipped every few million years. This was fundamental as it helps identify the age of the oceanic crust, by studying the youngest rocks at ridges and proves that the earth did once fit together.


What is the Benioff Zone


an area of seismicity corresponding with the slab being thrust downwards in a subduction zone. The different speeds and movement of rock at this point produce numerous earthquakes. It is the site of intermediate/deep-focused earthquakes


How do volcanoes form at constructive plate boundaries


At constructive margins, magma is less dense than the plate so rises above it, forming a volcano, such as those within the Rift valleys


How do volcanoes form at destructive plate boundaries


At destructive margins, subduction causes the melting of the oceanic plate, allowing for magma to rise on the crust to form a volcano. This produces explosive volcanos such as Mt St Helens.


Give the primary impacts of volcanic hazards

  • Pyroclastic flows - hot gasses and ash ejected as the shaft of a volcano
    collapses during an eruption – moves extremely fast
  • Tephra- volcanoes eject material such as rock fragments
  • Lava flows- extremely hot liquid that is ejected from certain volcanoes during
    an eruption – moves slow yet causes huge damage
  • Volcanic gasses - explosive eruptions - co2-carbon monoxide etc - most
    deaths from this - colourless and odourless

Give the secondary impacts of volcanic hazards


Lahars - volcanic mudflows generally composed of relatively fine sand and silt material. The degree of the hazard varies depending on the steepness of slopes, the volume of material and particle size. As a secondary hazard, they are associated with heavy rainfall as trigger as old tephra deposits on steep slopes can be re-mobilised into mudflows

Jokulhlaups – type of catastrophic glacial outburst flood. They are a hazard to people and infrastructure and can cause widespread landform modification through erosion and deposition. These floods occur very suddenly with rapid discharge of large volumes of water, ice and debris from glacial source.


Explain how an earthquake occurs


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


What is the hypocentre


is the ‘focus’ point within the ground where the strain energy of the earthquake stored in the rock is first released. The distance between this and the epicentre is called the focal length


Explain the differences between the three different types of seismic waves produced by an earthquake


Primary waves: vibrations caused by compression, these waves can travel through fluids and solids and are longitudinal. This also means that they transfer energy parallel to the direction of the wave, so if a wave is travelling north to south, the energy will be transferred in this direction.

Secondary waves: S-waves cannot travel through air or water, only through solids, but they have a larger amplitude (this is the height of a wave, measured from the highest point to the middle line) so are more destructive in the case of an earthquake. They are transverse waves, meaning they transfer energy perpendicular

Love waves: The final type of seismic wave occurs along the boundary between two different substances (e.g. rock and air). They can be either longitudinal or transverse. These waves travel slower than both S and P waves but have a higher amplitude and so can be the most destructive of all the seismic waves.


Give the primary impacts on an earthquake

  • Violent ground shaking
  • Building collapse
  • Ground splitting

Give and explain the secondary impacts on earthquakes


Soil liquification – This is the process by which water-saturated material can temporarily lose normal strength and behave like a liquid as a result of extreme shaking from an earthquake. The earthquake causes the water pressure to increase to the point where the soil particles can move easily, especially in poorly compacted sand and silt.

Landslides: Another important secondary hazard from earthquakes: where slopes weaken and fail. As many destructive earthquakes occur in mountainous areas, landslides can be a major secondary impact.


How are tsunamis formed


-Tsunamis are produced by sub-marine earthquakes at subduction zones, water
displacement and deep trough waves
- The movement of plates under the ocean causes an uplift of ocean water,
disrupting the sea bed


What physical and human factors does the impact of a tsunami depend on


 The duration of the event
 The wave amplitude, water column displacement and distance travelled
 The physical geography of the coast
 Timing of the event – quality of early warning systems
 The degree of coastal development and its proximity from the coast

  • However, the most serious events occur when the physical and human factors interact with each other to produce a disaster

What is a hazard


A perceived natural/geophysical event that has the potential to threaten both life and property.


What is a disaster


The realisation of a hazard, when it ‘causes a significant impact on a vulnerable population’. When 10 or more people are killed; when a 100 or more people are affected


Explain the complex relationship between risks, hazards and people.


 Unpredictability - Many hazards are not predictable; people may be caught
out by either timing or magnitude of an event

 lack of alternatives - People may stay in a hazardous area due to a lack of
options. This may be due to economic reasons, lack of space to move or a
lack of skills/knowledge

 Dynamic hazards - The threat from hazards is not constant, it may increase
or decrease over time.

 Cost-benefit - The benefits of a hazardous location may outweigh the risks
involved in staying there. Perception of a risk is also important here.


What is the hazard risk equation and what is the importance of it - giving examples

  • The hazard risk equation helps explain why similar hazards cause disasters
    at different degrees
  • For instance, both Izmit (Turkey) and Kashmir (Pakistan) had a similar size
    earthquake in 1999 and 2005. However, Kashmir had 75,000 deaths whilst Izmit
    had 18,000. This was because Kashmir is situated in a remote mountainous
    location with poor access to services/infrastructure which hinder capacity to
  • Thus, impacts of disasters vary according to levels of development.
  • For richer countries, there are high financial losses whilst poorer countries
    are left with severe shocks to community wellbeing and infrastructure – the
    poor are also vulnerable to secondary hazards, such as diseases, which may
    arise from the inability to receive international aid quickly
  • For the emerging world, such as India and China, disasters can slow growth and
    potentially destroy economic systems

What are the three scales used to measure earthquakes and explain their properties


Richter Scale - A measurement of the height and amplitude of the waves produced by an earthquake, it will measure the same on the Richter scale

Mercalli Scale - Measures the experienced impacts of an earthquake. It Is a relative scale, because people experience different amounts of shaking in different places. It is based on a series of key responses, such as people awakening, the movement of furniture and damage to structures

Moment Magnitude Scale (MMS) - A modern measure used by seismologists to describe earthquakes in terms of energy released. The magnitude is based on the ‘seismic moment’ of the earthquake, which is calculated from: the amount of slip in a fault, the area affected and the Earth-rigidity factor.


What scale is used to measure the size of a volcanic eruption


A relative measure of the explosiveness of a volcanic eruption, which is calculated from the volume of products, height of the eruption cloud and qualitative observations.


What is a tectonic hazard profile

  • A technique used to try to understand the physical characteristics of different
    types of hazards, for example earthquakes, tsunamis and volcanoes.
  • Hazard profiles can be used to analyse and assess the same hazards which
    take place in contrasting locations or at different times.
  • Hazard profiles are developed for each natural hazard and are based on
    criteria such as frequency, duration and speed of onset.

Giving examples explain how tectonic hazard profiles can be used to compare tectonic disaster

  • Earthquakes, volcanoes and tsunamis have different characteristics on terms of magnitude, speed of onset, duration, frequency and special probability.
  • Each disaster also varies in the destruction it causes. Impacts can either be social, economic or environmental as well as being direct/indirect, primary/secondary and long-term/short-term
  • Generally, the less developed a country, the more likely it is to face more sever social and economic impacts of a tectonic hazard

For example, both California and the Philippines are disaster hotspots but whereas 40 to 60% lie below the poverty line in the Philippines, only 20% do in California. This means, in the case of a disaster, the Philippines will have greater social impacts (as most of the poorly built infrastructure will be damaged) whilst California will face larger economic losses


How can development be negative in causing the disaster risk


Development can be a cause of a disaster risk

• Unsustainable development practices that create
unsafe working conditions
and reduce environment quality
• Development paths generating inequality,
promoting social isolation or
political exclusion


How can development be positive in reducing the disaster risk


• Access to safe drinking water, food and secure
dwelling places increase community resilience
• Development can build communities and broaden the
provision of opportunities for participation and
involvement in decision making, recognising excluded
groups such as women, and enhancing education,
health and well-being


How can inequality drive the disaster risk nexus

  • The social progress and power dynamics that drive
    the disaster risk-poverty nexus is strongly linked with
  • In the context of tectonics, inequality has a number of
    Impacts on disaster risk levels
  • Low income households are often forced to occupy
    hazard-exposed areas where there are low land
  • Such places have poor infrastructure and social
    protection; they are also likely to have high levels of
    environmental degradation
  • People in such areas often have low resilience as they
    have little voice in terms of political debate and
    influence, as well as being socially excluded and

What are the four different types of inequality that can effect the disaster risk nexus


o Asset inequality: relates to housing and security of tenure, as well as agricultural productivity (in farming communities) or goods and savings in trading communities

o Inequality of entitlements: refers to the unequal access to public services and welfare systems, as well as inequalities in the application of the rule of law

o Political inequality: unequal capacities for political agencies possessed by different groups and individuals in any society

o Social status inequality: is 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 to services.


How can disasters create development opportunities


Disasters create development opportunities

• Favourable environment for advocacy for disaster-risk
reduction measures
• Decision makers are more willing to allocate
resources in the wake of a disaster
• Rehabilitation and reconstruction activities create
opportunities for integrating disaster-risk measures


How can disasters limit or destroy development


• Destruction of physical assets and loss of production capacity, market
access and input materials
• Damage to infrastructure and erosion of
livelihoods and savings
• Destruction of health or education infrastructure
• Deaths, disablement and migration


How can Governance be a factor in contributing to a vulnerable population in terms of disaster risk


Economic Governance
Includes the decision-making processes that affect a country’s economic activities and its relationship with other economies. This has major implications for equity, poverty and people’s quality of life

Political Governance
Is the process of decision making to create policies, including national disaster reduction and planning. The nature of this process and the way it brings together the state, non-state and private-sector players/stakeholders determines the quality of the policy outcomes

Administrative Governance

Is the system of policy implementation and requires good governance at central and local levels. In the case of disaster risk reduction, it requires functioning enforcement of building codes, land use planning, environmental risk and human vulnerability monitoring and safety standards.


Evaluate what happened in the Icelandic Volcanic Ash Hazard of 2010


Why is Iceland a hotspot for Volcanic activity?

  • Iceland is located in a tectonically active area
  • The island is bisected by the northern part of the Mid-
    Atlantic Ridge, a constructive plate margin which
    diverging by about 23 mm per year.
  • Magma periodically rises between the plates at the
    surface as basaltic lava flows.

What happened in Spring 2010?

  • Volcano under the Eyjafjallajökull ice cap in south east
    Iceland erupted
  • The strata-volcano is a cone composed of alternating
    layers of ash and lava
  • There were two eruptions (March and April), with the
    second eruption occurring under the icecap which
    increased the explosivity of the event – 9km into

Primary Impacts of the eruption

  • Flooding: heat from the eruption melted vast amounts
    of ice under the ice cap - meltwater subsequently
    emerged from the edge of the ice cap as a glacial
  • Airport closure: Ash-fall closed Reykjavik airport for
    several days
  • Mudslides (lahars): ash mixed with meltwater and rain
    created mudslides or lahars

Secondary Impacts of the eruption

  • Overtime the ash spread onto Europe – causing
    widespread disruption to the European and North
    American Airspace
  • Entire UK airway system had to be closed
  • 100,000 flights cancelled
  • 10 million people stranded
  • 1.7 billion in losses for airlines – 5 billion to the
    European economy
  • Airports across Europe lost over 250 million


  • Further research into the effects on ash on aircraft.
  • Reconstruction of roads, local flood defences needed

Evaluate the Nyirangongo volcanic eruption in 2002


The volcano
- Mount Nyriragongo is an active stratovolcano with an
elevation of 3,470m in the Virunga Mountains
associated with the Albertine Rift.
- It is located inside Virunga National Park, In the
Democratic Republic of Congo

What happened in 2002?

  • After several months of increased seismic and
    fumarolic activity. A 13 km fissure opened in the south
    flank of the volcano, spreading in a few hours from
    2800 m to 1550 m elevation and reaching the
    outskirts of the city of Goma
  • Lava streamed from three spatter cones at the end
    of the fissure and flowed in a stream 200 to 1000 m
    wide and up to 2 m deep through Goma.


  • 147 people killed, 45 of which in the first 24 hours of
    the eruption killed by roofs crashing down due to the
    heavy ash, lava flows, and toxic gas
  • 14 villages were destroyed - Goma split in half by lava
  • 4500 buildings destroyed, making up 40% of Goma
  • Very large number lost their workplace, their
    employment and their income, as well as assets and
    savings (increase vulnerability no income)
  • 20,000 people left homeless – 300,000 evacuated

Secondary Impacts of the eruption

  • The volcano still emits gases which have reportedly killed children

Evaluate the Nepal Earthquake of 2015

  • Nepal is a developing country with a population of
    about 26.5 million people.
  • On 25 April 2015 a magnitude 7.8 earthquake struck
  • Nepal is a multiple hazard zone, with a steep
    mountainous landscape

Primary impacts

  • Approximately 9000 people lost their lives
  • More than 22,000 people were injured
  • More than half a million houses collapsed
  • Kathmandu airport shut

Secondary effects

  • Violence against women soared
  • Thousands of refugees
  • Starvation due to the limited supplies
  • Small outbreaks of cholera


  • The low level of development means that much of the
    local science is out of date
  • Nepal’s population is vulnerable. Poor and socially
    excluded groups are less able to absorb shocks than
    well-positioned and better-off households
  • Because of poverty, many people build their own
    houses, which are often built without the correct
    building codes

Evaluate the New Zealand earthquake of 2010

  • Magnitude 7.1 earthquake
  • Epicentre 40km from Christchurch
  • Lasted 40 seconds

Primary impacts

  • 1 person died
  • Sewers damaged
  • Electrical grid disrupted
  • Rail lines buckled
  • Soil liquification caused flooding

Secondary effects

  • Disruption to industrial production, goods exports and
    activity – however, this was relatively short lived as
    the region’s manufacturing hub escaped significant
  • Tourism industry suffered badly. The city of
    Christchurch had been the hub of tourist activity and
    many of its attractions were demolished


  • Indicators suggest that business activity had been
    quite resilient. Although business confidence dropped
    nationwide in the immediate aftermath of the 2011
    quake, they recovered quickly
  • Financial markets largely ignored he earthquake
  • Agricultural sector was largely unaffected

Evaluate the Indian ocean tsunami of 2004



  • Subduction caused by indo-Australian plate under
    Eurasian plate
  • 9.1 mag caused 20metre uplift in sea bed

Primary impacts

  • 14 countries affected
  • 250,000 killed
  • In Sumatra alone 130,000 were killed and 30,000 still
  • Thousands of villages destroyed

Secondary impacts

  • Diseases such as cholera spread quickly, especially in
    refugee camps


  • No early warning systems in place – as it occurred in
    a relatively impoverished area
  • Huge amounts of poverty – very few structures could
    withstand the tsunami

Explain the trends in Tectonic disasters

  • At a global scale, deaths have decreased whilst
    economic losses have risen. This is because the
    global economy and wealth is greater than what it was
  • The use of international aid and preparedness means
    that less people are affected by disasters now than in
  • The number of tectonic hazards has fluctuated having
    peaked in 1997 and 200, reaching an all-time low in
    the early 1980s and 2012

What are Hydro-meteorological Hazards


‘a process or phenomenon of atmospheric, hydrological or oceanographic nature that may cause loss of life, injury or other health impacts, property damage, loss of livelihoods and services, social and economic disruption, or environmental damage

(includes tropical cyclones, thunderstorms, hailstorms, tornados, blizzards, heavy snowfall, avalanches, coastal storm surges, floods including flash floods, drought, heatwaves and cold spells).’


What are multiple hazard zones

  • Multi-hazard zones are where a number of physical
    hazards combine to create an increased level of risk
    for the country and its population
  • For the Philippine’s, there is a complex mix of
    geophysical and hydro-meteorological hazards as the
    plate boundaries intersect a major storm belt in an
    area of high population density - The Philippine’s
    faces explosive volcanic threats, landslides,
    earthquakes, typhoons, tsunamis, drought and
  • These locations are often seen as disaster hotspots

Explain why earthquakes are difficult to predict

  • Prediction accuracy depends on the type of tectonic
    hazard; a volcano can be monitored for likely eruptions,
    but tectonic plates move randomly so earthquakes
    cannot be predicted accurately

Evaluate the importance of a communities resilience to a natural hazard - include Parks model


The United Nations Office for Disaster Risk Reduction stresses on the importance of improving a community’s resilience to natural hazards. They highlight the vitality of adopting multiple management techniques to prevent hazards from becoming disasters (these include preventing flooding by utilising sandbags on coasts, whilst improving warning systems)

  • Parks disaster response curve can be used as a
    framework to better understand the time dimensions
    of resilience
  • 4 stages: Pre-disaster, Relief, Rehabilitation and
  • In the event of a tectonic disaster these four factors will
    define a communities future resilience
  • It takes into account that different hazard events have
    different impacts so vary in their duration, speed and
    destruction of quality of life.
  • The less developed a country, the greater the impacts
    and destruction of quality of life – the disaster onset is
    slower as secondary hazards worsen the death tolls.

What are micro and macro hazard management approaches


 Micro: strengthening individual buildings and structures against hazardous stress
 Macro: large-scale protective measures designed to protect whole communities


Give methods of hazard management approaches for earthquakes


o Hard resistant designs: Hospitals, police stations, pipelines, schools and factories have been strengthened with improvements such as cross-bracing, deep foundations and resistant materials
o Land-Use Zoning: Create policies on where it is the safest to build infrastructure


Give methods of hazard management approaches for volcanos


o Diversion flows: Lava can be diverted by spraying sea water to cool and solidify the flow – this was achieved in Iceland in 1973, saving the fishing port and harbour that were the economic lifelines of the populations


Give methods of hazard management approaches for tsunamis


o Tsunami walls: work for a given amplitude or threshold of the wave
o Mangrove restoration: slow the speed of the wave. 70,000 trees were planted after the 2004 tsunami


What strategies can be used in terms of modification of a hazard in terms of vulnerability

  • Modification of a hazard can involve a number of
    approaches and adaptions including:

 Prediction, forecasting warnings
 Improvements in community preparedness
 Working with groups and individuals to change

  • High-Tech Monitoring: international satellites and aircraft monitor changes in the earth, for instance GNS Science in New Zealand use light detection and ranging to create 3D data pieces of the Earth’s surface. Changes to the surface pinpoint the likelihood of a disaster
  • Prediction: Observing changes in volcanic shapes or low magnitude earthquakes could suggest whether a disaster is likely
  • Education: Teaching communities about hazards and protection enables the community to gain strength and withstand shock better
  • Community preparedness: Earthquakes drills and alarms prepare communities for how best to protect themselves in a disaster

How can loss as a result of a tectonic disaster be modified


Disaster aid

  • Aid flows to countries and victims via governments,
    NGOs and private donors. In the longer-term aid is used
    for relief, rehabilitation and reconstruction.
  • This type of aid is often appropriate to middle- and lower-
    income countries

Internal governmental aid

  • This is typically used in emerging and developing
    countries where the disaster mitigation is achieved by
    spreading the financial load throughout the tax payers of
    the country.
  • This may include a national disaster fund and release of
    funds may require a political declaration.

What is the equation for a hazard


Risk=hazard × exposure × vulnerability/(manageability )


Philippines 1991 (lahars impact case study)

  • Annual rainfall at Mount Pinatubo ranges from 80 inches
    (2,000 millimeters) on the volcano’s northeast flank to
    more than 160 inches (4,000 millimeters) on its summit
    and southwest flank.
  • Ash and other deposits from Mount Pinatubo’s 1991
    eruption destroyed or buried much of the lush
    vegetation that had covered the volcano.
  • When rainfall in Pinatubo exceeded about 0.5 inches (12 millimeters) in 30 minutes, rapid runoff down the still
    bare slopes quickly grew into torrents that became lahars by eroding these deposits.
  • When the largest and fastest lahars reach the lowlands surrounding Pinatubo, they have speeds of more than
    20 miles (32 kilometers) per hour, are as much as 30 feet (10 meters) thick and 300 feet (100 meters) wide, and
    can transport more than 35,000 cubic feet (1,000 cubic meters) of debris and mud per second.
  • Since the 1991 eruption, lahars from Pinatubo have destroyed the homes of more than 100,000 people. With
    most old stream channels filled, lahars can now spread widely on the gentle slopes and lowlands surrounding
    Mount Pinatubo, threatening successors to the early dams and levee

How prepared is Japan for an earthquake


Japan’s P-wave system includes more than 1,000 seismometers, which are instruments designed to detect and record earthquakes.

At the mouth of Kamaishi Bay on the northeast coast stands the a 20-metre-thick barrier, which is 2 km long. It rises to 8 metres above the water and is anchored to the sea floor 63 metres down and Completed in 2008 after 30 years, it cost of more than US$ 1.4 billion.


How much of Tokyos buildings are earthquake proof


In Tokyo, 87% of buildings are reportedly built to withstand earthquakes.


1906 San Fran Cisco earthwyake


The 1906 San Francisco earthquake struck the coast of Northern California

Devastating fires soon broke out in the city and lasted for several days. As a result, up to 3,000 people died and over 80% of the city of San Francisco was destroyed.