Tectonics

Question 1

What are the key features of the global distribution of tectonic hazards?

Answer 1

• They occur at specific points, usually associated with tectonic plate boundaries
• Distribution is uneven - some areas more at risk
• Can occur at, divergent/convergent/conservative plate boundaries
• Often generate multiple hazards where they occur
• Earthquakes also occur where the Indo Australian plate collides with the Eurasian plate - collision zone

Question 2

What are the two different types of tectonic plates?

Answer 2

• Oceanic - make up the ocean floor, high density not very thick
• Continental - thicker, make up earths landmasses, less dense

Question 3

Where are the other areas an earthquake or a volcano occur?

Answer 3

• Earthquakes can occur in mid plate settings - ancient fault lines being reactivated
• Volcanoes can occur at a hotspot where there is mantl plume - the plume remains stationary although the plate above moves slowly - over time continuing plate movement produces a chain of volcanic islands

Question 4

What are the key features of earthquakes?

Answer 4

• As the earths crust is mobile a build up of stress within the rocks can take place
• When this stress is suddenly released parts of the surface experience an earthquake
• Much of the energy released is transferred vertically to the surface and moves outwards from the epicentre as seismic waves
• At the moment of fracture rocks may regain their original shape but in a new position

Question 5

What is the depth focus of an earthquake?

Answer 5

• Shallow earthquakes cause the most damage - 75% energy released
• Deeper earthquakes have much less effect

Question 6

What are the three types of seismic waves from earthquakes?

Answer 6

• P waves - fastest but cause least damage
• S waves - shake the ground violently
• L waves - travel only across surface and have a large amplitude and cause a lot of damage

Question 7

What are some secondary hazards associated with earthquakes?

Answer 7

• Landslides - especially in mountainous areas - eg - Nepal

- Liquefaction

Question 8

What secondary hazards are associated with volcanoes?

Answer 8

• Lahars: fast mud flows

- Flooding: glacial bursts

Question 9

What are the key features of tsunamis?

Answer 9

• Most are generated by submarine earthquakes at subduction zones
• Seabed is vertically displaced
• They have very long wavelengths
• Short in amplitude, 1m in height and barely noticeable
• Travel quickly
• Closer to the land = height increase
• Hit coastline as a train of waves
• Water is drawn back and up by the approaching tsunami

Question 10

When does a hazard become a disaster?

Answer 10

• 10 or more deaths
• 100 or more affected
• $1 million economic loss

Question 11

Whats the hazard risk equation?

Answer 11

risk = hazard x vulnerability/capacity to cope

Question 12

What are some of the ways communities can increase their resilience?

Answer 12

• Emergency evacuation routes in place
• Land use planning to reduce numbers at risk
• Having hazard resistant designs

Question 13

What is the PAR model?

Answer 13

• States that risk is a function of vulnerability and hazard
• Nature of hazard is important (volcano/earthquake etc.)
• Socioeconomic context is vital - political status, investment levels, education level etc.
• Both the root causes and the hazard place pressure on a location
• Release comes with a reduction in the vulnerability of the location affected
• All these factors are dynamic and therefore makes it hard to manage safety

Question 14

What are some of the impacts of tectonic hazards?

Answer 14

• Environmental: damage to or destruction of ecosystems
• Social: deaths, injuries, psychological impacts
• Economic: loss of property, infrastructure, businesses

Question 15

Key points of earthquake magnitudes

Answer 15

• Energy released is measured by the moment magnitude scale

- Damaging effects are measured by the Mercalli scale

Question 16

Key points of volcano magnitudes

Answer 16

• Measured by the VEI - based on volume, duration and column height of ejections
• can be related back to the type of boundary the volcano is on

Question 17

Key points of comparing hazards

Answer 17

• compared using hazard profiles

- hazard profiles include; magnitude, speed of onset, duration, frequency, areal extent and spatial predictability

Question 18

What are the events that present the most risk?

Answer 18

• high magnitude + low frequency
• have large areal extents
• tend to occur at subduction zones and collision zones
• rapid speeds of onset with low spatial predictability

Question 19

Key features of inequality

Answer 19

• inequality of access to things like; education, healthcare, housing, income - affects vulnerability and resilience
• locations with low HDI = high levels of vulnerability due to things like; lack of basic needs, lack of education, healthcare is poor

Question 20

What geographical factors influence vulnerability and resilience?

Answer 20

• population density - highly populated areas are hard to evacuate
• isolation and accessibility

Question 21

Initial points about trends and patterns

Answer 21

• frequency of tectonic hazards has remained static
• number of people affected has increased
• hydro-meteorological hazards are more common (cyclones, floods, storms)

Question 22

Key features of earthquakes since 1980

Answer 22

• number of disasters have been 15 and 40 per year
• deaths have been variable in this time period
• economic losses have increased

Question 23

Key features of volcanoes since 1980

Answer 23

• Number of disasters less than earthquakes and deaths are much lower
• only 7 eruptions have killed more than 100 people
• wider impacts can be great as large scale evacuation is needed

Question 24

Key features of mega disasters

Answer 24

• some very large tectonic disasters have taken place in the collision zone of the Himilayas - Nepal (2015)
• major earthquake events - Haiti
• Japan earthquake and tsunami had worldwide economic impacts
• the Iceland eruption had a global social and economic impact

Question 25

Multiple hazard zones (California) are….

Answer 25

• geologically young with unstable mountains prone to landslide
• tectonically active and earthquakes and eruptions are common
• often on major storm tracks either in the mid latitudes or on tropical cyclone tracks
• at risk from global climate perturbations such as ENSO

Question 26

Key points on the hazard management cycle

Answer 26

• Response - immediate help
• Recovery - rebuilding infrastructures
• Preparedness - community education
• Mitigation - acting to reduce scale of next disaster

Question 27

Key points of the park disaster response model

Answer 27

• illustrates how quality of life is impacted by a hazardous event
• shows how a range of management strategies can be used over time - from before and after the event
• highlights the roles of emergency relief agencies and rehabilitation
• shows how different areas affected may have different response curves depending on their level of preparedness and economic development