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Geography A-Level > Tectonic Hazards > Flashcards

Tectonic Hazards Flashcards

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1
Q

How old is Earth?

A

4.6 billion years old

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2
Q

Where do tectonic hazards occur?

A

plate boundaries

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3
Q

Continental Drift theory/Pangaea was proposed by and when?

A

Alfred Wegener in 1912

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4
Q

Asthenosphere

A
  • bottom half of mantle
  • solid
  • highly viscous
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5
Q

Lithosphere

A
  • top half of mantle
  • more molten liquid
  • crust
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6
Q

4 theories for plate movement:

A
  • mantle convection
  • slab pull
  • subduction zone movement
  • sea floor spreading
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7
Q

Slab pull

A

sinking oceanic crust

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8
Q

Subduction zone movement

A

destroyed crust

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9
Q

Sea floor spreading

A

mid-ocean ridges

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10
Q

Types of plate boundaries

A
  • divergent
  • convergent
  • conservative
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11
Q

Divergent

A
  • drift apart

- most commonly found at mid-ocean ridges so sea-floor spreading occurs

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12
Q

Convergent

A
  • connect

- lighter oceanic crust is subducted underneath continental crust

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13
Q

Conservative

A
  • consists of transform faults
  • two plates sliding past each other at different directions or same direction but different speeds, creating friction which releases energy = earthquake
  • the San Andreas fault
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14
Q

Formation of volcanic hotspots/intra-plate activity

A

Hotspots are formed when the outer core heats up the mantle, causing its density to change, becoming magma.

The magma then rises from the asthenosphere to the lithosphere through a conduit, as a result of density change, and spreads out in a bulbous shape in the upper mantle due to plate movement, thus creating the plume, which is an area of high level heat in the mantle.

The magma escapes onto the sea floor through weaknesses or burns through the crust which cools and hardens as it reaches sea, forming new land.

Over time, this process repeats and eventually the build of land rises above sea level, resulting in an active volcanic island.

The volcano remains active until movement of the crust shifts it away from the mantle plume, forming a chain of islands such as the Hawaiian Islands.

The main type of volcano created by this process is a shield volcano.

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15
Q

Evidence supporting Pangaea

A
  • dovetailing
  • paleomagnetism
  • mid-atlantic ridge
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16
Q

Formation of an earthquake

A
  • earthquakes are caused by sudden movements near the Earth’s surface along a fault
  • plate movement creates a build up of tectonic strain, creating a store of energy
  • when the pressure exceeds the strength of the fault, the crust fractures
  • this sudden release of energy creates seismic waves which radiate outwards
  • the crust rebounds near the fracture which causes the ground shaking felt on the surface
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17
Q

3 types of waves

A
  • p-waves
  • s-waves
  • l-waves
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18
Q

P-Waves

A
  • primary waves
  • pressure on rock
  • push and pull rock
  • caused by compression
  • spread quickly from focus
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19
Q

S-Waves

A
  • secondary waves
  • slower then p
  • vibrate at right angles
  • cannot travel through liquids
  • more destructive than p
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20
Q

L-Waves

A
  • love waves
  • high amplitude
  • cause damage on surface
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21
Q

What factors increase severity of an earthquake in terms of waves?

A
  • amplitude

- frequency

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22
Q

Which 2 waves are most destructive and why?

A
  • S and L

- larger amplitude and frequency

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23
Q

Primary earthquake impacts

A

ground shaking

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24
Q

Secondary earthquake impacts

A
  • liquefaction
  • landslides/avalanches
  • aftershocks
  • crustal fracturing
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25
Q

Composite/Strato volcano

A
  • steep sided
  • thick, viscous lava
  • explosive
  • rare
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26
Q

Shield volcano

A
  • gently-sloped
  • low viscosity
  • gentle, non-explosive eruptions
  • frequent (Hawaii)
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27
Q

Primary volcano impacts

A
  • pyroclastic flow
  • lava flows
  • tephra and ash cloud
  • gas eruptions
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28
Q

Secondary volcano impacts

A
  • lahars

- jokulhlaups

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29
Q

Factors which intensify volcanic eruptions

A
  • magma viscosity
  • plate margins
  • explosiveness of eruption
  • ejected materials
  • proximity to population
  • frequency of eruptions
  • prediction, forecasts + reaction
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30
Q

Factors affecting viscosity of magma

A
  • temperature
  • dissolved gases
  • chemistry/content = silica
31
Q

Types of magma

A
  • basic = high temp + proportion of dissolved gases + low silica content
  • acid = low temp + proportion of dissolved gases + high silica content = higher viscosity
32
Q

Pyroclastic flow

A

fast-moving current of clouds of incandescent gas, ash and rocks

33
Q

Lava flow - What? Characteristic?

A
  • a mass of flowing or solidified lava

- slow-paced so people are able to out-run them, however, lava flows damage/incinerate everything in their way

34
Q

Tephra and ash fall

A

tephra defines all piece of all fragments of rock ejected int the air by an erupting volcano

35
Q

Lahars

A

fast cement-like mudflows consisting of volcanic and water

36
Q

Jokulhlaups

A

glacial run or glacial outburst flood

37
Q

Pyroclastic flow examples/figures

A
  • 1900s: Mount Pelée killed all but 2 of its 29,000 residents in Saint-Pierre
38
Q

Lava flow examples/figures

A
  • 2014-2015: Fogo volcano in Cape Verde engulfed 75% of buildings within 3 villages
39
Q

Lahar examples/figures

A
  • since 1991 Pinatubo eruption in the Philippines, more than 100,000 homes
    have been destroyed
40
Q

Tephra and ash fall/cloud examples/figures

A

2010: Ejyafjallajökul
- 100 000 commercial flights canceled
- European economy lost $5 billion
- Kenya laid off 5 000 workers after flowers and vegetables were left rotting in airports so industry lost $1.3 million a day
- a no-fly zone imposed so airlines lost £130 million a day

41
Q

How is a tsunami formed?

A

Tsunamis can be caused by sub-marine earthquakes at subduction zones as a result of sea-bed and water column displacement

42
Q

Why are tsunamis hard to detect far away from shore?

A

They don’t gain height until they reach shallow water

43
Q

Why do tsunamis grow in height as they go closer to shore?

A

Tsunami waves become compressed near the coast, shortening the wave length, which directs the wave energy upward, hence increasing height

44
Q

Risk of tsunami

A
  • hard to detect out at sea
  • grows in height in shallow water
  • series of waves/wave train
  • first wave not necessarily the largest or most destructive
  • long wavelength can lengthen the duration between the waves
  • extreme risk if people return thinking the tsunami is over
45
Q

2011 Japanese Tsunami impacts

A
  • 15-20 000 deaths which 65% were over 60 years old
  • over £300 billion economic cost
  • destroyed 95% of all vegetation
  • over 400 aftershocks greater than 5.0 magnitude after 5 weeks
  • over 70% of all structures in the port city of Ishinomaki were destroyed
  • Fukushima nuclear power plant evacuation and nuclear meltdown
46
Q

2011 Japanese Tsunami factors affecting hazard risk

A
  • magnitude 9.0 on Richter Scale

root causes:

  • false sense of security on sea wall which fell by a meter due to a plate shift
  • protection systems could only cope up to an 8.0 magnitude
  • nuclear power plant on coast in Fukushima = exposure to radiation

dynamic pressures:

  • population density: Tokyo has 37 million inhabitants
  • ageing population, 65% of nearly 20 000 deaths were over 60 years old

unsafe conditions in PAR model:

  • 70% of Japan is mountainous
  • soft reclaimed land is susceptible to ground shaking, causing landslides
  • Japan sits on a plate boundary
  • most tectonically active: 30% of earthquakes annually are in Japan
47
Q

2004 Boxing Day Tsunami factors affecting hazard risk

A
  • high magnitude of 9.0 on the Richter scale
  • impacted 14 countries directly
  • infrequent events in countries in the Indian Ocean meant a lack of experience in coping with such hazards
  • political instability in Sri Lanka and Indonesia meant that aid and relief was slow
  • flat and low-lying islands like the Maldives and Phuket
  • no warning system in the Indian Ocean
  • LICs/NEEs
  • densely populated tourist areas on the coast
48
Q

2004 Boxing Day Tsunami social impacts

A

Primary:

  • nearly 300 000 people died or went missing
  • half died in Indonesia and 80% of the province was destroyed
  • 4 million people fell into poverty

Secondary:

  • spreading of malaria and cholera
  • lack of safe water and sanitation lead to many deaths among the very young due to water-borne diseases
49
Q

2004 Boxing Day Tsunami economic impacts

A
  • over £9 billion cost of damage
  • 60% of Sri Lanka’s fishing fleet destroyed
  • Phuket dropped 80% of their foreign visitors in 2005
50
Q

2004 Boxing Day Tsunami environmental impacts

A
  • mangrove forests along the coast were destroyed
51
Q

2008 Sichuan Earthquake social impact

A
  • over 80 000 deaths , 10 000 were students
52
Q

2008 Sichuan Earthquake economic impact

A
  • over £100 billion economic cost nearly £200 billion
53
Q

2008 Sichuan Earthquake factors affecting hazard risk

A

root causes:

  • mud-brick houses
  • poor infrastructure
  • poor governance

dynamic pressures:

  • rapid birth rate: 1950s - large population = power
  • rapid urbanization
54
Q

2002 Nyiragongo volcanic eruption social impacts

A
  • 400 000 evacuated
  • over 10 000 homes destroyed by ash and lava
  • over 100 000 homeless
  • 150 pharmacies buried under 2 meters of lava
  • 2/4 hospitals buried under 2 meters of lava
  • food strain as poisonous gases caused acid rain which affected farmland and cattle
55
Q

2002 Nyiragongo volcanic eruption economic impacts

A
  • over 300 000 depended on on aid

- aviation fuel stores exploded as lava flow damaged Goma airport, stopping trade and aid

56
Q

2010 Haiti earthquake root causes

A
  • heavily in debt to banks like the US: used little available money for debt repayments, rather than improving the country’s infrastructure
  • 80% of population lived below poverty line: less than €2 a day
  • 30-40% of government budget came from foreign aid
57
Q

2010 Haiti earthquake dynamic pressures

A
  • lack of urban planning
  • lack of disaster management systems
  • rapid urbanization = slum-housing
  • high-population density of 3 million inhabitants in Port-au-Prince
58
Q

2010 Haiti unsafe conditions

A
  • slum housing

- low GDP per capita

59
Q

2015 Nepal earthquake human factors increasing risk

A
  • multi-story buildings in Kathmandu = landslides and avalanches in the Himalaya mountains = blocking roads, slowing down aids
  • old, religious, historic buildings
60
Q

2015 Nepal earthquake physical factors increasing risk

A
  • 75% of country is mountainous
61
Q

4 ways of measuring the magnitude and intensity of tectonic hazards

A
  • Richter scale for earthquake
  • Mercalli scale for earthquake
  • Moment Magnitude scale for earthquake
  • Volcanic Explosivity Index for volcanoes
62
Q

Richter scale pros n cons

A

+ easier comparison
+ popular, well-known = well understood globally

  • inaccurate estimates for large magnitude
  • outdated, old (1935)
63
Q

Mercalli scale pros n cons

A
  • subjective

- considered unscientific as it relies on eyewitness accounts

64
Q

Moment Magnitude scale pros n cons

A

+ better at measuring larger earthquakes = more reliable

  • poor for measuring small earthquakes: becomes inaccurate below 3.5
65
Q

VEI pros n cons

A
  • Volcanic Explosivity Index

+ easy to compare eruptions

  • doesn’t take into account radius of ejected materials
  • doesn’t take into account density and amount of gases
66
Q

What is measured in a hazard profile?

A
  • magnitude
  • speed of onset
  • duration
  • areal extent
  • spatial predictability
  • frequency
67
Q

DRC (Nyiragongo) social indicator facts

A

HDI: 0.5
Life expectancy: 60
GNI: $900

68
Q

UK social indicators to compare w other countries

A

HDI: 0.9
Life expectancy: 80
GNI: $43k

69
Q

2010 Haiti earthquake impacts

A
  • over 300 000 died

- over 1 million homeless

70
Q

Factors affecting vulnerability and resilience in Haiti

A

Asset inequality: 80% of population live below poverty line of $2 a day

Inequality of entitlements: over 1 000 murders in 2012

Political inequality: government annual budget $1 billion compared to £802 billion in the UK

Social status: 61% literacy rate

  • life expectancy 62 years
  • low level preparedness: destruction of transport, communications, civil centers and loss of personnel = loss of connectivity
  • least developed country in the Western Hemisphere
71
Q

Japan’s characteristics decreasing its vulnerability and increasing its resilience

A

Asset inequality:

  • 75% of buildings are built with earthquake resistant design
  • GNI per capita over $45 000

Inequality of entitlements:
- less than 1 murder per 100 000 of population

Political inequality:
- over $60 billion spent on infrastructure

Social status:
- 98% literacy rate

72
Q

Haiti impacts due to being poor

A
  • manually lifting rubble: only 5% cleared after a year
  • performing amputations w basic equipment
  • World Bank suspending all debt and an intention to cancel it altogether
73
Q

Earthquake management

A
  1. Modify the event
    - 87% of Tokyo buildings are earthquake resistant
    - bullet trains equipped w earthquake sensors that triggers all moving trains to freeze = 2011 no deaths and injuries
  2. Modify vulnerability
    - technology: phones - emergency alert - TVs - earthquake coverage on where to seek protection and if tsunamis are approaching
    - education: children in earthquake simulators
  3. Modify losses
    - Earthquake insurance
    - disaster relief
  4. Modify causes
    - landslides: prevented by constructing gutters and altering the slope gradient

Geography A-Level (4 decks)

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