Tectonic Processes and Hazards Flashcards

1
Q

How do the plates move at a conservative margin?

A

Plates move parallel to each-other

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2
Q

How do plates move at a divergent margin?

A

Move apart

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3
Q

How do plates move at a constructive margin?

A

Move apart

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4
Q

How do plates move at a convergent margin?

A

Move towards each-other

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5
Q

Which plate is denser: oceanic or continental?

A

Oceanic plate

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6
Q

What happens at a convergent margin between an oceanic and continental plate?

A

The oceanic plate subducts underneath the continental plate. This forms a deep ocean trench

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7
Q

What happens to the oceanic plate after subduction?

A

It melts in the asthenosphere. This causes slab pull

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8
Q

What happens to the continental plate after the oceanic plate subducts?

A

The continental crust is squashed together and forced upwards, forming fold mountains

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9
Q

What is the Benioff zone?

A

The part of a subducted oceanic plate at which the friction with the continental plate causes deep earthquakes

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10
Q

Describe the traditional theory of tectonic plate movement?

A

Mantle convection; convection currents in the magma causes the plates above the mantle to move

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11
Q

What is the seafloor-spreading theory?

A

Hot magma forced out of the asthenosphere hardens to form mid-ocean ridges, forming new oceanic crust

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12
Q

What is the modern theory of tectonic plate movement?

A

Slab pull

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13
Q

What is slab pull?

A

Subducting crust is denser than the mantle around it because it is cooler; it sinks and pulls the rest of the plate with it

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14
Q

Who proposed the theory of continental drift, and when?

A

Wegener, 1912

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15
Q

Who proposed the movement of plates by convection current, and when?

A

Holmes (1930)

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16
Q

When was paleomagnetism introduced?

A

1960s

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17
Q

How did paleomagnetism advance plate tectonic theory?

A

Polar shifts show the age of the rocks; getting older the further away they are from mid-ocean ridges

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18
Q

What type of volcano is formed at fold mountains?

A

Composite volcano

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19
Q

What is the other name for hotspots?

A

Mantle plume

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20
Q

What type of volcano is formed at constructive margins?

A

Shield volcano

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21
Q

What type of waves are P-Waves?

A

Longitudinal

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22
Q

What type of wave are S-Waves?

A

Transverse

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23
Q

How do L-Waves move?

A

Transverse; oscillate parallel to the surface

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24
Q

How fast does an S-wave move?

A

60% the speed of a P-Wave

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25
Q

Which is faster - S-Wave or L-Wave?

A

S-Wave

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26
Q

What is jökulhlaup?

A

Glacial flooding caused by a volcanic eruption

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27
Q

What is a Lahar?

A

A hot mudflow moving down a volcano’s river valley.

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28
Q

What is pyroclastic flow?

A

Hot gas and tephra moving at 700km/h

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29
Q

What is tephra?

A

Volcanic matter

30
Q

What is Degg’s disaster model?

A

Venn diagram with Hazard and Vulnerable population, intersecting to cause a disaster

31
Q

What is the Disaster Risk Equation?

A

(Hazard x Vulnerability) ÷ Capacity to Cope

32
Q

What are the criteria for a disaster?

A

10+ deaths
100+ affected
£1m

33
Q

What are the factors of the Pressure and Release model?

A

Root Causes
Dynamic Pressures
Unsafe Conditions
(Hazard Event)

34
Q

What are the components of a Hazard profile?

A

Magnitude, Speed of Onset, Duration, Areal Extent, Spatial Predictability, Frequency

35
Q

What is liquefaction?

A

Surface rocks lose strength and become almost liquid. They can’t support foundations

36
Q

What is a mantle plume?

A

A rising convection current in the mantle pushes up through the crust. Can be in middle of plate (Hawaii) or on a boundary (Iceland)

37
Q

How do plates move at a collision margin?

A

Move towards each-other

38
Q

What kind of plates are involved at a collision margin?

A

Two continental plates

39
Q

Give an example of a collision margin

A

Himalayas

40
Q

What kind of mountains are formed at a collision margin?

A

Fold mountains

41
Q

Which kind of earthquake wave causes the most damage?

A

Love waves

42
Q

How fast does a tsunami move at deep sea?

A

800 km/h

43
Q

How large is a tsunami at deep sea?

A

1m high, 100km wide

44
Q

How have the number of people affected by disasters changed over time?

A

Increased

45
Q

How have the number of reported disaster events changed over time?

A

Increased

46
Q

How have the cost of disasters changed over time?

A

Increased

47
Q

How have the number of people killed by disasters changed over time?

A

Decreased

48
Q

How can you predict a volcanic eruption?

A

Changes in the types of gas emitted

Magma moves nearer to the surface; can cause small earthquakes

49
Q

What is the drawback to volcanic eruption prediction?

A

Not an exact science - 3 evacuations before Mt St Helens

50
Q

What are the stages of the hazard management cycle?

A

Hazard Event, Response, Recovery, Mitigation, Preparedness

51
Q

How are poorer countries limited in terms of the hazard management cycle?

A

They can only perform the response stage with the help of aid

52
Q

What is the Park model?

A

A graph of Quality of Life against Time for a hazard event

53
Q

How does the Park model suggest Quality of Life changes after a hazard event?

A

Sharp decline, gradual return to normality

54
Q

How can wealthy countries use the Park model?

A

To improve their situation compared to normality

55
Q

How are poorer countries affected by the Park model?

A

Slower return to normality; lower Quality of Life

56
Q

What are the three stages of the Park model?

A

Response (weeks)
Reconstruction (months)
Mitigation (years)

57
Q

What methods are there for modifying a hazard event?

A

Land-use zoning, tsunami defences (walls), lava flow diversion, cross bracing (aseismic buildings)

58
Q

What methods are there for modifying the vulnerability of the population?

A

Education (community preparedness), high-tech monitoring, earthquake survival kits

59
Q

What factors affect the impact of a hazard event?

A

Population Growth, Urbanisation, Ageing Population, HDI, Loss of Community Memory, Corrupt Governance, Technology

60
Q

How effective is international aid in the short-term after a hazard event?

A

A lot of money/support provided; good organisation

61
Q

How effective is international aid in the long-term after a hazard event?

A

The world “forgets” because of less media coverage

62
Q

How does the effect of insurance differ between countries?

A

People in poorer countries can’t afford it

It is a luxury for richer nations

63
Q

What theory of plate movement is related to seafloor-spreading?

A

Ridge push

It is now proven to provide negligible force

64
Q

When was ridge push shown to provide negligible driving force for tectonic plate movement?

A

1983

65
Q

Where is an earthquake’s epicentre?

A

The point on the surface directly above the focus

66
Q

Where is an earthquake’s focus?

A

The origin of the earthquake

67
Q

What physical damage do earthquake waves cause?

A

Crustal fracturing

68
Q

What are the criteria for a disaster?

A

10 people dead
100 people affected
£1 million damage

69
Q

How often does a VEI 4 eruption occur?

A

18 months

70
Q

How often does a VEI 6 eruption occur?

A

50 - 100 years