Tectonics

Question 1

What is a hazard

Answer 1

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.

Question 2

What can the earths crust be divided into

Answer 2

• 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)

Question 3

Explain the three differences between plate boundaries

Answer 3

• 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
  other

Question 4

Explain Plate Tectonic Theory

Answer 4

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.

Question 5

What is a mid ocean ridge

Answer 5

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

Question 6

What is sea floor spreading

Answer 6

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

Question 7

What is Palaeomagnetism and explain the significance of

Answer 7

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.

Question 8

What is the Benioff Zone

Answer 8

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

Question 9

How do volcanoes form at constructive plate boundaries

Answer 9

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

Question 10

How do volcanoes form at destructive plate boundaries

Answer 10

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.

Question 11

Give the primary impacts of volcanic hazards

Answer 11

• 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

Question 12

Give the secondary impacts of volcanic hazards

Answer 12

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.

Question 13

Explain how an earthquake occurs

Answer 13

 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

Question 14

What is the hypocentre

Answer 14

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

Question 15

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

Answer 15

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.

Question 16

Give the primary impacts on an earthquake

Answer 16

• Violent ground shaking
• Building collapse
• Ground splitting

Question 17

Give and explain the secondary impacts on earthquakes

Answer 17

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.

Question 18

How are tsunamis formed

Answer 18

-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

Question 19

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

Answer 19

 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

Question 20

What is a hazard

Answer 20

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

Question 21

What is a disaster

Answer 21

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

Question 22

Explain the complex relationship between risks, hazards and people.

Answer 22

 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.

Question 23

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

Answer 23

• 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
  cope.
• 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

Question 24

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

Answer 24

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.

Question 25

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

Answer 25

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.

Question 26

What is a tectonic hazard profile

Answer 26

• 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.

Question 27

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

Answer 27

• 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

Question 28

How can development be negative in causing the disaster risk

Answer 28

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

Question 29

How can development be positive in reducing the disaster risk

Answer 29

• 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

Question 30

How can inequality drive the disaster risk nexus

Answer 30

• The social progress and power dynamics that drive
  the disaster risk-poverty nexus is strongly linked with
  inequality
• 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
  values
• 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
  marginalised

Question 31

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

Answer 31

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.

Question 32

How can disasters create development opportunities

Answer 32

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

Question 33

How can disasters limit or destroy development

Answer 33

• 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

Question 34

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

Answer 34

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.

Question 35

Evaluate what happened in the Icelandic Volcanic Ash Hazard of 2010

Answer 35

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
  atmosphere

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
  burst
• 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

Responses

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

Question 36

Evaluate the Nyirangongo volcanic eruption in 2002

Answer 36

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.

Impacts

• 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
  flows.
• 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

Question 37

Evaluate the Nepal Earthquake of 2015

Answer 37

• 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
• 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

Evaluation

• 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

Question 38

Evaluate the New Zealand earthquake of 2010

Answer 38

• 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
  damage
• Tourism industry suffered badly. The city of
  Christchurch had been the hub of tourist activity and
  many of its attractions were demolished

Evaluation

• 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
  impact
• Agricultural sector was largely unaffected

Question 39

Evaluate the Indian ocean tsunami of 2004

Answer 39

Context

• 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
  missing
• Thousands of villages destroyed

Secondary impacts

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

Evaluation

• 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

Question 40

Explain the trends in Tectonic disasters

Answer 40

• 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
  before
• The use of international aid and preparedness means
  that less people are affected by disasters now than in
  1960.
• The number of tectonic hazards has fluctuated having
  peaked in 1997 and 200, reaching an all-time low in
  the early 1980s and 2012

Question 41

What are Hydro-meteorological Hazards

Answer 41

‘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).’

Question 42

What are multiple hazard zones

Answer 42

• 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
  flooding.
• These locations are often seen as disaster hotspots

Question 43

Explain why earthquakes are difficult to predict

Answer 43

• 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

Question 44

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

Answer 44

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
  Reconstruction
• 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.

Question 45

What are micro and macro hazard management approaches

Answer 45

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

Question 46

Give methods of hazard management approaches for earthquakes

Answer 46

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

Question 47

Give methods of hazard management approaches for volcanos

Answer 47

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

Question 48

Give methods of hazard management approaches for tsunamis

Answer 48

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

Question 49

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

Answer 49

• 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
behaviours

• 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

Question 50

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

Answer 50

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.

Question 51

What is the equation for a hazard

Answer 51

Risk=hazard × exposure × vulnerability/(manageability )

Question 52

Philippines 1991 (lahars impact case study)

Answer 52

• 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

Question 53

How prepared is Japan for an earthquake

Answer 53

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.

Question 54

How much of Tokyos buildings are earthquake proof

Answer 54

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

Question 55

1906 San Fran Cisco earthwyake

Answer 55

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.