Tectonics

Question 1

What is a hazard and what causes them?

Answer 1

• 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).

Question 2

Where do geophysical hazards occur?

Answer 2

• Geophysical hazards occur near plate boundaries. These plates move at different speeds and directions which can cause collisions, earthquakes and volcanic activity as shown in the map above.

Question 3

What is an intra-plate earthquake and what causes them?

Answer 3

• Earthquakes can also occur near the middle of plates (called intra-plate). The
  causes of this are not fully understood but it is assumed that plates have pre-existing weaknesses which become reactivated, forming seismic waves. For example, an intraplate earthquake may occur if solid crust, which has weakened overtime, cracks under pressure.

Question 4

What are volcanic hotspots and what causes them?

Answer 4

• Volcanic hotspots, such as the Ring of Fire, are also situated amongst the centre of plates. This is a localised area of the lithosphere (Earth’s crust and upper mantle) which has an unusually high temperature due to the upwelling of hot molten material from the core. At hotspots, such as the Hawaii hotspot, magma rises as plume

Question 5

What are some areas of high tectonic activity?

Answer 5

• OFZ (Oceanic Fracture Zone) – This is a belt of activity through the oceans and along the mid-ocean ridges through Africa, the Red Sea, the Dead Sea
• CFZ (Continental Fracture Zone) – This is a belt of activity along the mountain ranges from Spain through the Alps to the Middle East and to the Himalayas.

Question 6

What has the trend of tectonic hazards been like since the 1960s?

Answer 6

• The total number of recorded hazards has increased.
• The number of fatalities has decreased, but there are some spikes during mega
  disasters.
• The total number of people being affected by tectonic hazards is increasing, due to population growth.
• The economic costs associated with hazards and disasters has increased significantly.
• This is partly due to increases in development as infrastructure in more developed countries costs more to repair.
• Also, increasing number of insurance policies, especially in developed countries, heightens the costs.

Question 7

Why is measuring disaster impacts hard?

Answer 7

• Depends on whether you look at the direct deaths so those killed in the disaster straight away or indirectly by looking at how many people died of diseases that spread after the disaster. Some impacts take time to become apparent.
• The location is important as rural and isolated areas are hard to reach and so it may be hard to collect data from them. Similarly, data may be difficult to collect in areas with very high population densities.
• Different methods may be used by different organisations so as a result different sources may quote different numbers of deaths and injuries
• The number of deaths quoted by a government could be subject to bias. For example, during the 2004 Indian Ocean tsunami, the Burmese government claimed there were 0 deaths Burma. This may be to try and show that the government is doing a good job in terms of aid, protection etc.

Question 8

What are the four sections of the Earth?

Answer 8

• Crust - Also known as the lithosphere. The uppermost layer of the Earth which is
  thinnest, least dense and lightest. Oceanic crust is only 7km thick, whereas continental crust can be up to 70km thick.
• Mantle - May also be called the asthenosphere. Largely composed of silicate rocks, rich in iron and magnesium. The mantle is semi-molten and a temperature gradient (towards the core) generates convection currents. This causes to the circulation of the mantle and may contribute to the lithosphere’s plate tectonic movement. The mantle is at a depth from 700km to 2890km below the crust.
• Outer Core - Dense, semi-molten rocks containing iron and nickel alloys. At a depth of 2890km to 5150km below the Earth’s surface.
• Inner Core - Similar composition to the outer core. It’s over 5150km below the
  Earth’s crust. The inner core is solid due to the extreme pressures it experiences.
  The core’s high temperature is a result of:

Question 9

What happens when a continental and oceanic plate is on a destructive plate boundary?

Answer 9

• Denser oceanic plate subducts
  below the continental.
• 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.
• Pressurised 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.

Question 10

What happens when two oceanic plates are on a destructive plate boundary?

Answer 10

• Heavier plate subducts leaving an
  ocean trench. Fold mountains will
  also occur.
• Built up pressure causes
  underwater volcanoes bursting
  through oceanic plate.
• Lava cools and creates new land
  called island arcs.

Question 11

What happens when two continental plates are on a destructive plate boundary?

Answer 11

• 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
  lithosphere due to pressure between
  plates.
• Fold mountains formed from piles
  of continental crust.

Question 12

What happens when two oceanic plates are on a constructive plate boundary?

Answer 12

-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 (as the floor
  spreads and gets wider).

Question 13

What happens when two continental plates are on a constructive plate boundary?

Answer 13

• 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.

Question 14

What are the other forces influencing how plate boundaries occur?

Answer 14

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.

Question 15

What is a conservative plate boundary?

Answer 15

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.

Question 16

What are the different types of seismic waves?

Answer 16

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

Question 17

What are the secondary hazards of an earthquake?

Answer 17

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.

Question 18

What is soil liquefaction?

Answer 18

• Secondary hazard of earthquakes
• 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.

Question 19

What are landslides?

Answer 19

• Secondary hazard of earthquakes
  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.

Question 20

What are tsunamis?

Answer 20

• Secondary hazards of earthquakes
• 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.

Question 21

What factors contribute to the impacts of a tsunami?

Answer 21

• Population density of area hit, if the population is higher than more people are likely to be affected
• Coastal defences (e.g. Tsunami waves)
• Duration of the event
• Wave amplitude and distance travelled
• 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

Question 22

What are lava flows?

Answer 22

• Primary hazard of volcanoes
• 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 (the
  explosivity and viscosity depends on silicon dioxide content)

Question 23

What are pyroclastic flows?

Answer 23

• Primary hazard of volcanoes
• Pyroclastic flows – This is a mixture of hot dense rock, lava, ash and gases which
  move very quickly along the surface of the Earth. Due to their high speeds,
  pyroclastic flows are extremely dangerous and can cause asphyxiation for anyone
  unfortunately caught by the flow.

Question 24

What are tephra and ash flows?

Answer 24

• Primary hazard of volcanoes
• When pieces of volcanic rock and ash are blasted into the air. This can cause serious damage to buildings, which can collapse under the weight of ash or tephra.

Question 25

What are volcanic gases?

Answer 25

• Primary hazard of volcanoes
• Volcanic gases – Gases like sulphur dioxide and carbon monoxide are released
  into the atmosphere. Due to their potency, volcanic gases can travel long distances.

Question 26

What are Lahars?

Answer 26

• Secondary hazard of volcanoes
  Lahars – Combination of rock, mud and water which travel quickly down the sides
  of volcanoes. These can occur when the heat of the eruption causes snow and ice to melt or alternatively when an eruption coincides with heavy rainfall.

Question 27

What are jokulhlaups?

Answer 27

• Secondary hazard of volcanoes
• Snow and ice in glaciers melt after an eruption which causes sudden
  floods that are very dangerous .

Question 28

What is acid rain?

Answer 28

• Secondary hazard of volcanoes
• caused when gases such as sulfur dioxide are released into the atmosphere.

Question 29

What is the definition of a disaster?

Answer 29

• 10 or more people are killed and/or 100 or more people are affected

Question 30

What is the Degg model?

Answer 30

• Show the relationship between a vulnerable population a hazard and when they overlap cause a disaster.

Question 31

What is the PARK model?

Answer 31

• 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).

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

Question 32

What is the pressure and release model?

Answer 32

• The Pressure and Release Model is used to analyse 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.

Root causes
+
Dynamic pressure
+ Naturalhazard=disaster
Unsafe conditions

Question 33

What are tectonic hazard profiles?

Answer 33

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 were 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 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.

Question 34

How can the effectiveness of models be evaluated?

Answer 34

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)?

Question 35

What is the Volcanic explosivity index?

Answer 35

• 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).

Question 36

What is the modified mercalli scale?

Answer 36

• Measures the destructiveness of an
  earthquake.
• It is a relative scale as people would feel different amounts of shaking in different places.
• It 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.

Question 37

What is the moment magnitude scale?

Answer 37

• Measures the amount of energy released in earthquake.
• Scale from 0-9.
• It’s a simple measure, so
  environmental or social
  impacts must be inferred.

Question 38

What is the richter scale?

Answer 38

• 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.

Question 39

How can volcanic hazards be prevented?

Answer 39

• cant be prevented, only by moving people out of range of the volcanic hazards?

Question 40

How can people become prepared for volcanic hazards?

Answer 40

• Monitoring volcano activity and giving out warnings, tremors, changes to the top surface of the volcanoes, changes to the tilt of the volcano.
• Education on volcanic eruptions so people know what to do in an event
• Planned evacuation procedures
• Response teams can be trained

Question 41

How can volcanic eruptions be mitigated?

Answer 41

• Physical blocks to stop lava flows from reaching key areas
• Strengthening buildings at risk of mudflow or ash pileup
• Evacuation and exclusion zones
• ## Planning emergency aid and rescue

Question 42

How can volcanic eruptions be adapted to?

Answer 42

• Moving away from the area
• Capitalise on benefits such as rich soil and tourism
• Change profession to become less vulnerable to hazards

Question 43

What is land use zoning and the costs and benefits?

Answer 43

Preventing building on low
lying areas and areas of
high risk

Benefits
Low cost
Reduces vulnerability

Costs
Stops economic
development on some high
value land
Strict enforcement required

Question 44

What are resistant buildings and the costs and benefits?

Answer 44

Buildings with deep
foundations, sloped roofs so
that ash doesn’t build and
create pressure

Benefits
Can help prevent collapsing
Protects people and
property

Costs
High cost for larger buildings
Low income families cannot
afford this

Question 45

What are tsunami defences and the costs and benefits?

Answer 45

Sea walls which stop waves
travelling inland

Benefits
Reduces damage
Provides security

Costs
Very high cost
Doesn’t look nice
Can be overtopped

Question 46

What is lava diversion and the costs and benefits?

Answer 46

Barriers and water cooling
to divert and slow down lava
flow

Benefits
Diverts lava away
Low cost

Costs
Only works for low VEI lava

Question 47

How can vulnerability be monitored?

Answer 47

Hi Tech Scientific Monitoring
Monitors volcano behaviour and predict eruptions

Benefits
Predicting eruption is possible in some cases
Warning and evacuation can help save lives

Costs
Costly, in LDCs, volcanoes aren’t usually monitored Doesn’t prevent property damage

Community
Preparedness and Education

Benefits
Low cost and often implemented by NGOs
Can save lives through small
actions

Costs
Doesn’t prevent property damage
Harder to implement in isolated rural areas

Adaptation
Moving out of harm’s way and relocation

Benefits
Helps save lives and property

Costs
High population densities prevent it
Disrupts people’s traditional home and traditions

Question 48

How can loss be modified?

Answer 48

Short term aid
Search and rescue and also
food, water, aid and shelter

Benefits
Can help reduce death toll
by saving lived and keeping
people alive until long term
aid is provided

Costs
High costs and technical
difficulties in isolated areas
Emergency services are
limited and are poorly
equipped in LDC

Long term aid
Reconstructions plant to
rebuild an area and improve
resilience

Benefits
Reconstruction can help
improve resilience through
land use planning and better
construction methods

Costs
Very high costs
Needs are quickly forgotten
by the media shortly are the
disaster

Insurance
Compensation to replace
losses

Benefits
Allows people to recover economically for paying reconstruction

Costs
Doesn’t help save lives
Not many in LDCs have insurance

Question 49

What is the role of local communities in reducing the impacts of an event?

Answer 49

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.

Question 50

What is the role of NGOs and TNCS in reducing the impacts of an event?

Answer 50

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

Question 51

What are the types of inequalities impacting the resilience of communities?

Answer 51

• 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 rule of law.

Question 52

What factors contribute to a populations vulnerability?

Answer 52

• 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 affected by a
  hazard.
• Geography isolation and accessibility - remote, rural areas often have poor transport links which can negatively effect rescue efforts.
• Level of urbanisation - 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.

Question 53

What is the role of governance in the impacts of an event?

Answer 53

▪ 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 programmes 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.

Question 54

What are the characteristics of a mega disaster?

Answer 54

Large scale disaster affecting a large spatial areas or large population.

▪ They pose problems in effective management to minimise the impacts.

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

▪ Mega Disasters are low probability (rare).

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