Tectonics

Question 1

What are the characteristics of an oceanic plate?

Answer 1

• Between 5-8km thick
• Deep beneath the oceans
• Less than 200mln years old
• Consists mainly of of dense/heavy rock (basalt)

Question 2

What are the characteristics of a continental plate?

Answer 2

• Between 30-70km thick
• Beneath the earths continental land masses and under shallow seas
• As old as 4bln years
• Consists of less dense/lighter rock (granite)

Question 3

What is a convergent plate margin?

Answer 3

• Two plates moving away from each other

Question 4

What is a divergent plate margin?

Answer 4

• Two plates moving towards each other

Question 5

What is a conservative plate margin?

Answer 5

• Two plates moving in different directions at different speeds
• Two plates moving in the same direction at different speeds

Question 6

What processes influence plate movement?

Answer 6

• Slab pull
• Ridge push
• Convection currents

Question 7

What is slab pull?

Answer 7

• Tectonic plate movement
• Subduction of the plate at oceanic trenches into the mantle

Question 8

What is ridge push?

Answer 8

• Magma rising pushes the ocean floor upwards
• Earth’s gravitational pull causes the crust to sink away from the ridge, causing it to cool and become more dense

Question 9

What do divergent plate margins create with continental plates?

Answer 9

• Rift Valleys

Question 10

What are convection currents?

Answer 10

• Movement of warm mantle magma

Question 11

What is a hotspot?

Answer 11

• Mantle plume of rising magma

Question 12

What is a hazard profile?

Answer 12

• Compares the physical processes of hazards
• Magnitude, duration, speed at onset, spatial predictability, frequency and areal extent

Question 13

What is the Mercalli scale?

Answer 13

• Measures the effect of an earthquake through observable, subjective data

Question 14

What is the Richter scale?

Answer 14

• Quantitive measure of an earthquake’s magnitude

Question 15

What is the VEI?

Answer 15

• Volcanic explosivity index
• Describes size of explosive volcanic eruptions based on intensity and magnitude

Question 16

What are the qualities of basaltic lava?

Answer 16

• Low in silica content - low viscosity
• Fluid magma
• Effusive eruptions

Question 17

What type of volcano does basaltic lava come from?

Answer 17

• Shield volcano

Question 18

What are the qualities of andesitic lava?

Answer 18

• High in silica content - high viscosity
• Solidifies on the way up to the surface
• Very explosive due to trapped gas

Question 19

What type of lava does cinder cone and composite volcanoes produce?

Answer 19

• Andesitic lava

Question 20

What are the characteristics of a composite volcano?

Answer 20

• Associated with subduction at convergent plate boundaries
• Slopes ranging up to 30 degrees
• Consists of many layers of ash, lava, tephra, pumice
• Violently explosive eruptions

Question 21

What are the characteristics of a shield volcano?

Answer 21

• Effusive eruptions
• Associated with mantle plumes
• Built almost entirely of fluid lava flows
• Gentle slopes of 2-10 degrees

Question 22

What are the characteristics of a cinder cone?

Answer 22

• Generally explosive
• Steep conical hill of tephra
• Commonly found on the side of a volcano
• Most are monogenetic
• Mostly <200m high
• Very little strength

Question 23

What are primary volcanic hazards?

Answer 23

• Lava
• Pyroclastic flows
• Tephra
• Volcanic gases

Question 24

What are secondary volcanic hazards?

Answer 24

• Lahars
• Jokulhaulps

Question 25

What is a P wave?

Answer 25

• The fastest seismic wave
• Can move through solids, liquids, and gases
• Oscillate ground back and forth in direction of travel

Question 26

What is a S wave?

Answer 26

• Shake the ground in a shearing motion, perpendicular to the direction of travel
• Can travel through solids

Question 27

What is soil liquefaction?

Answer 27

• Water saturated material can temporarily behave as a liquid

Question 28

What are landslides?

Answer 28

• When material on a (near) vertical surface falls

Question 29

How deep is a deep focus?

Answer 29

300km - 700km

Question 30

How deep is an intermediate focus?

Answer 30

70km - 300km

Question 31

How deep is a shallow focus?

Answer 31

0km - 70km

Question 32

What is the disaster risk equation?

Answer 32

• R = H x V / C
• R = risk
• H = hazard frequency
• V = vulnerability
• C = coping capacity

Question 33

What are the root causes of vulnerability?

Answer 33

• Limited access to power, resources, structures
• Political and economic systems

Question 34

What are the dynamic pressures of vulnerability?

Answer 34

• Lack of training, local investment, press freedom
• Deforestation
• Rapid population change
• Rapid urbanisation

Question 35

What are unsafe conditions for vulnerability?

Answer 35

• Local economy
• Physical environment
• Social relations
• Public actions

Question 36

How can you modify vulnerability and resilience?

Answer 36

• Predictions and warnings
• Community preparedness
• Land use planning

Question 37

How can you modify the loss?

Answer 37

• Accepting that hazards will occur
• Responding to the loss via aid or insurance

Question 38

How can you modify the event?

Answer 38

• Hazard prevention
• Hazard resistant design

Question 39

What are some examples of hazard prevention?

Answer 39

• Lubricate fault lines
• Divert lava away

Question 40

What are some examples of hazard resistant design?

Answer 40

• Cross bracing
• Shear walls
• Counter weights
• Shock absorbers/base isolators

Question 41

What are the limitations of designing earthquake resistant infrastructure?

Answer 41

• Difficult/unable to test infrastructure
• Technology is rapidly developing and things can become out of date quickly
• People living in low development countries can’t afford to build earthquake resistant infrastructures

Question 42

What are the limitations of strengthening existing structures to be more earthquake resistant?

Answer 42

• Seismic retrofitting is not as strong as new earthquake resistant infrastructure