Tectonics Flashcards
1
Q
What are the characteristics of an oceanic plate?
A
- Between 5-8km thick
- Deep beneath the oceans
- Less than 200mln years old
- Consists mainly of of dense/heavy rock (basalt)
2
Q
What are the characteristics of a continental plate?
A
- 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)
3
Q
What is a convergent plate margin?
A
- Two plates moving away from each other
4
Q
What is a divergent plate margin?
A
- Two plates moving towards each other
5
Q
What is a conservative plate margin?
A
- Two plates moving in different directions at different speeds
- Two plates moving in the same direction at different speeds
6
Q
What processes influence plate movement?
A
- Slab pull
- Ridge push
- Convection currents
7
Q
What is slab pull?
A
- Tectonic plate movement
- Subduction of the plate at oceanic trenches into the mantle
8
Q
What is ridge push?
A
- 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
9
Q
What do divergent plate margins create with continental plates?
A
- Rift Valleys
10
Q
What are convection currents?
A
- Movement of warm mantle magma
11
Q
What is a hotspot?
A
- Mantle plume of rising magma
12
Q
What is a hazard profile?
A
- Compares the physical processes of hazards
- Magnitude, duration, speed at onset, spatial predictability, frequency and areal extent
13
Q
What is the Mercalli scale?
A
- Measures the effect of an earthquake through observable, subjective data
14
Q
What is the Richter scale?
A
- Quantitive measure of an earthquake’s magnitude
15
Q
What is the VEI?
A
- Volcanic explosivity index
- Describes size of explosive volcanic eruptions based on intensity and magnitude
16
Q
What are the qualities of basaltic lava?
A
- Low in silica content - low viscosity
- Fluid magma
- Effusive eruptions
17
Q
What type of volcano does basaltic lava come from?
A
- Shield volcano
18
Q
What are the qualities of andesitic lava?
A
- High in silica content - high viscosity
- Solidifies on the way up to the surface
- Very explosive due to trapped gas
19
Q
What type of lava does cinder cone and composite volcanoes produce?
A
- Andesitic lava
20
Q
What are the characteristics of a composite volcano?
A
- 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
21
Q
What are the characteristics of a shield volcano?
A
- Effusive eruptions
- Associated with mantle plumes
- Built almost entirely of fluid lava flows
- Gentle slopes of 2-10 degrees
22
Q
What are the characteristics of a cinder cone?
A
- Generally explosive
- Steep conical hill of tephra
- Commonly found on the side of a volcano
- Most are monogenetic
- Mostly <200m high
- Very little strength
23
Q
What are primary volcanic hazards?
A
- Lava
- Pyroclastic flows
- Tephra
- Volcanic gases
24
Q
What are secondary volcanic hazards?
A
- Lahars
- Jokulhaulps
25
What is a P wave?
- The fastest seismic wave
- Can move through solids, liquids, and gases
- Oscillate ground back and forth in direction of travel
26
What is a S wave?
- Shake the ground in a shearing motion, perpendicular to the direction of travel
- Can travel through solids
27
What is soil liquefaction?
- Water saturated material can temporarily behave as a liquid
28
What are landslides?
- When material on a (near) vertical surface falls
29
How deep is a deep focus?
300km - 700km
30
How deep is an intermediate focus?
70km - 300km
31
How deep is a shallow focus?
0km - 70km
32
What is the disaster risk equation?
- R = H x V / C
- R = risk
- H = hazard frequency
- V = vulnerability
- C = coping capacity
33
What are the root causes of vulnerability?
- Limited access to power, resources, structures
- Political and economic systems
34
What are the dynamic pressures of vulnerability?
- Lack of training, local investment, press freedom
- Deforestation
- Rapid population change
- Rapid urbanisation
35
What are unsafe conditions for vulnerability?
- Local economy
- Physical environment
- Social relations
- Public actions
36
How can you modify vulnerability and resilience?
- Predictions and warnings
- Community preparedness
- Land use planning
37
How can you modify the loss?
- Accepting that hazards will occur
- Responding to the loss via aid or insurance
38
How can you modify the event?
- Hazard prevention
- Hazard resistant design
39
What are some examples of hazard prevention?
- Lubricate fault lines
- Divert lava away
40
What are some examples of hazard resistant design?
- Cross bracing
- Shear walls
- Counter weights
- Shock absorbers/base isolators
41
What are the limitations of designing earthquake resistant infrastructure?
- 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
42
What are the limitations of strengthening existing structures to be more earthquake resistant?
- Seismic retrofitting is not as strong as new earthquake resistant infrastructure
