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Natural Hazards Flashcards

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1
Q

What is a Natural Hazard?

A
  • A natural event that has had a huge social impact
  • (not considered hazard in a remote area where it isn’t seen as a threat)
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2
Q

What are the different examples of a Natural Hazard?

A
  • Volcanic eruption
  • Earthquake
  • Storms
  • Tsunami (huge wave caused by earthquake)
  • Landslides
  • Floods
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3
Q

What are the 3 main types of Natural Hazard?

A
  • Atmospheric hazards
  • Geological hazard
  • Flooding
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4
Q

What is Hazard Risk?

A

The chance or probability of being affected by a natural event

  • live close to river, risk of flooding
  • live close to sea, risk of tsunami
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5
Q

Why would people put themselves in risk of a hazard? (hazard risk)

A
  • weigh up advantages and disadvantages
  • events are unlikely to happen so they decide to accept small risk
  • have little choice/knowledge of the danger in their areas
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6
Q

What factors increase risk of natural hazard?

A

Poverty
Urbanisation
Climate change
Farming

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7
Q

How does Urbanisation increase hazard risk?

A
  • Over 50% of world population live in cities
    Some large global cities (Tokyo, LA, Istanbul) are at risk of earthquakes
  • Densely populated urban areas are at risk of earthquakes and cyclones.
    2010 Haiti earthquake destroyed the capital Port-au-Prince, killing 230,000 people
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8
Q

How can Poverty increase hazard risk?

A
  • may force people to live in areas at risk

Lima, Peru and Caracas, Venezuela-> lack of housing, forced to live on unstable slopes prone to flood/landslide

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9
Q

How can Climate change increase hazard risk?

A
  • atmosphere has more energy -> leads to more intense storms + hurricanes
  • cause some areas to become wetter, increase flooding risk
    cause other areas to become drier, increase drought and famine risk
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10
Q

How can Farming increase hazard risk?

A
  • When a river floods, it deposits fertile silt onto floodplain, which is good for farming, but NOT to live there.
  • River Ganges, Bangladesh. People are at risk living in floodplains in low-lying countries
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11
Q

What is an Earthquake?

A

A sudden and violent period of ground shaking

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12
Q

What is an Earthquake commonly caused by?

A

Sudden movement of rocks within the earth’s crust
- mainly at margins of tectonic plates (plates are moving, build up of pressure then released)

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13
Q

What causes Earthquakes that don’t occur at plate margins?

A
  • human activity (underground mining, oil mining)
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14
Q

How thick are tectonic plates?

A

100km

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15
Q

What are Tectonic plates?

A

Plates that the Earth’s crust is split up into

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16
Q

What are the 2 types of Tectonic plate?

A
  • Dense, thin, oceanic crust
  • Less dense, thick, continental crust
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17
Q

Why do Tectonic plates move?

A

Due to convection current from the Earth’s core
Gravitational sliding

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18
Q

What happens at a Constructive plate margin?

A

The plates move apart and new curst forms as magma rises towards the surface

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19
Q

What happens at a Destructive plate margin?

A

The plates move towards each other. The denser, oceanic plate may subduct (sink) under the less dense continental plate.
- Gravity pulls the oceanic plate into the mantle, dragging the plate away from the constructive margin

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20
Q

What does Tectonic activity at plate margins cause?

A

Earthquakes and Volcanoes

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21
Q

What is a Volcano?

A

A large and often conical-shaped landform usually formed over a long period of time by a series of eruptions

  • usually occurring in long belts along plate margins
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22
Q

How can Volcanoes form?

A
  • fed by magma (hot molten rock) from deep within the earth, rising to surface at constructive and destructive plate margins
  • at hot spots, magma can break through thin crust to surface (ie Hawaiian Islands)
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23
Q

What are the 3 types of plate margins + where can you find them?

A

Constructive- where 2 plates are moving apart
Destructive- where 2 plates are moving towards each other
Conservative (transform)- where 2 plates are sliding alongside one another

  • Found in Iceland
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24
Q

What happens at the Constructive margin in Iceland?

A

The 2 plates move apart
- Magma forces it way to the surface along mid-Atlantic Ridge, causing earthquakes as it breaks crust
- Forms volcanoes as it reaches surface
- Magma at constructive margins is hot and fluid-> erupting lava flows far before cooling. This creates broad and flat shield volcanoes

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25
Q

Where is Iceland?

A

The North Atlantic Ocean

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26
Q

What happens at a Destructive Margin in South America?

A

The 2 plates move towards each other
- Deep trench forms where the 2 plates meet-> Denser, Oceanic (Nasca) plate is subducted under the less dense, continental (South America) plate
- Friction between the 2 plates causes earthquakes
- The oceanic plate melts in the mantle, creating magma.
- This magma (less fluid than at constructive margin) breaks through the surface, forming a steep-sided composite volcano (with violent and explosive eruptions)

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27
Q

What happens when 2 continental plates meet?

A

The plates collide and the crust crumples and uplifts.
- forms fold mountains (Himalayas)
- the process causes earthquakes

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28
Q

Why does 2 continental plates meeting NOT cause volcanoes?

A

There isn’t any magma at collision margins

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29
Q

What happens at a Conservative margin in California?

A

2 plates move past each other, friction between the plates causes earthquakes
- San Andreas Fault, California: Pacific plate (faster moving) slides in same direction as North American plate (slower moving)

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30
Q

How do Earthquakes/Volcanoes happen at conservative margins?

A

Earthquakes happen as stress builds over time. Can be destructive as is close to Earth surface.
- Released when plates slip/shift
-NO volcanoes, no magma

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31
Q

What are Primary and Secondary effects?

A

Primary: caused by ground shaking. (deaths, injury, damage to roads and buildings)

Secondary: result of primary effects (tsunami, fires, landslides)

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32
Q

What are examples of Responses to Earthquakes?

A

Emergency care, support and help with long-term reconstruction

33
Q

What is the GNI of Japan and Nepal?

A

Japan- $41,690 (24th)
Nepal- $1090 (163th)

out of 192 countries
GNI= Measure of a country’s wealth

34
Q

What is the HDI of Japan and Nepal?

A

Japan- 19th
Nepal- 142nd

out of 189 countries

HDI= Measure of a country’s development

35
Q

What were the effects of the Natural Hazards in Japan?

A

March 2011
9.0 magnitude earthquake
100km off coast
slippage of destructive plate margin (North American plate + Pacific plate)
Shifted earth off axis
3-5 mins of ground shaking
giant tsunami waves, 30 mins for waves to hit
10m high waves (overtopped tsunami defence walls), surged 10km upstream

36
Q

How did Natural Hazards affect Nepal?

A

Earthquake
- 25 April 2015
- 7.9 Richter scale
- 80km NW of capital, Kathmandu
- Destructive margin, Indo-Australian plate colliding with Eurasian plate (45mm per year)-> collision + pressure formed Himalayas
- 15km below surface (shallow)
- severe ground shaking, landslides, avalanches
- caused damage in India, Tibet, Pakistan

37
Q

What were the Primary effects in Japan?

A
  • Violent ground shaking, up to 5 mins (buildings collapsed- deaths + injuries)
  • Ground shaking, destroyed 1000’s of homes
  • Roads + rail lines damaged, electricity cut off, water + sewerage disrupted
  • 4 millions in NE Japan left without electricity, 1.5 without water
  • Fukushima dam burst
  • US$235 (most expensive global natural disaster)
38
Q

What were the Secondary effects in Japan?

A
  • 10m high tsunami wave, caused most of the 18,000 deaths + 500,000 homeless attributed to the earthquake
  • Waves destroyed port facilities, infrastructure, homes
  • 1000’s left without electricity, water, sanitation, left living in temp shelters for months
  • Explosion at Fukushima nuclear power plant, led to evacuation of 100,000 (fear of radioactive leak)
39
Q

What were the Primary effects in Nepal?

A

Ground shaking
- 9000 dead, 20,000 injured, over 8 million affected (1/3 of population)
- 3 million left homeless
- Electricity, water supplies, communication affected
- 1.4 million needing food, water, shelter for days after
- 7000 schools + hospitals
- International airport congested as aid arrived
- 50% of shops destroyed (food supply + livelihood affected)
- US$5 Billion

40
Q

What were the Secondary effects in Nepal?

A

Fires, landslides
- blocked roads, stopping relief efforts
- Avalanche on Mnt Everest-> killed 19 people (greatest loss of life on the mountain)
- blocked the Kali
- Gandaki river-> evacuate area in case of flooding
- NO tsunami-> Earthquake on land

41
Q

What is the history of Continental Drift?

A

1912, Alfred Wegener used geological evidence (ie fossils) to suggest continents were once connected together (called Pangea)
- he suggested they floated apart due to continental drift
- now we know that the drift is due to plate tectonic mechanisms

42
Q

What is the Plate Tectonics theory?

A

The outermost solid layer of earth (crust) is divided into solid tectonic plates up to 100km thick

43
Q

What is Gravitational sliding?

A

The effect of gravity on plate movement

44
Q

What are the 2 mechanisms of Gravitational sliding?

A

Ridge push and Slab pull

45
Q

What is Ridge Push?

A

At Constructive plate margins
- fresh magma rises at mid-ocean ridge
- 2 plates forces apart at ridge by magma
- mid-ocean ridge elevation is higher than seabed, causes plates to slide downwards

46
Q

What is Slab Pull?

A

At Destructive plate margins
- gravity acts upon thicker, denser plate
- causing it to sink, ‘pulling’ the rest of the plate with it

47
Q

How do convection currents work?

A
  • radioactive decay occurs in earth core, generates heat, heats mantle at base
  • hot rock rises to surface + cools
  • reaches crust, forced sideways (can’t pass solid rock), cools + becomes dense and sinks back to core
  • once more in contact with core again, reheated, rises to surface
48
Q

What scale are earthquake magnitudes measured on?

A

Richter scale

49
Q

What is the name of the Iceland volcano?

A

Eyjafjallajokull

50
Q

What are the 2 types of responses to earthquakes?

A
  • Immediate responses
  • Long term responses
51
Q

What are immediate responses to earthquakes?

A
  • search + rescue
  • keeping survivors alive, providing medical care, food, water, shelter
52
Q

What are long term responses to earthquakes?

A
  • re building and reconstruction
  • aim of returning life back to normal + reducing future risk
53
Q

How do the responses from Japan and Nepal compare?

A

Earthquakes and tsunamis are common in Japan
- 1st September, country partakes in Earthquake drill
- scientific monitoring + warning systems. 2011, 15 min warning for approaching tsunami waves

Earthquakes are common in Nepal
- pattern, very large earthquakes occur every 80 years or so
- despite warnings + new building regulations-> lack of preparation for 2014 earthquake

54
Q

What were Japan’s immediate responses?

A
  • Search + Rescue teams from Japan/abroad. 100,000 members of Japanese Self Defence Force
  • 500,000 evacuated to higher ground pre tsunami. Homes destroyed, needed shelter, food, water.
  • Within few weeks some roads + railways restored, improving access to region
  • Power soon restored, intermittent supply due to Fukushima nuclear power plant explosion (tsunami)
55
Q

What were Japan’s Long-term responses?

A
  • Reconstructive Design Council built long term plan (identify zones of reconstruction etc), budget = over US$150m
  • Tax incentives promoted investment into industry + business
  • early 2015, most of debris cleared + new housing away from low lying coastal land
  • 2020, nearly 300,000 housing units complete (replace temporary homes)
  • Restored industrial production, farmland + seafood processing plants
  • 2013, upgraded tsunami warning system-> faster, accurate forecasts. 12.5m wall
56
Q

What were Nepal’s immediate responses?

A
  • International Search + Rescue teams. Water and medical support-> UK, India, China
  • 1.4 million people-> water, food, shelter. World Vision International, provided emergency food kits for 8000, shelter kits for 20,000
  • Helicopter rescue for people stuck in avalanche on MNT Everest + delivered supplies to villages cut off by landslide
  • Red Cross set up field hospitals over 500,000 tents set up
  • over 300,000 migrated from Kathmandu (seek shelter + support)
57
Q

What were Nepal’s long term responses?

A
  • 2018: new National Disaster Risk Reduction Policy
  • 2015 end, most access roads repaired, landslides cleared
  • Mnt Everest trekking restored, tourist return (country income)
  • UNESCO working with government to restore 700 temples, palaces + museums
  • Nepal Earthquake Housing Reconstruction Project: $US700 million, grants to rebuild disaster resilient homes using techniques
58
Q

Why do people live near tectonic hazards/hazardous areas?

A
  • Large earthquakes and volcanic eruptions do not happen a lot, so aren’t seen as a major threat
  • People living in poverty may focus on other daily issues (money, family, food, security)
  • Plate margins often coincide with favourable areas of settlement (ie near the coast where there are port developments)
  • Some may not be aware of the risks living near plate margins
  • Volcanoes can bring benefits of fertile soils, rocks for building, rich mineral deposits and hot water
  • Fault lines associated with earthquakes can bring water to the surface-> important in dry desert regions
  • More effective monitoring of volcanoes and tsunamis, people can be warned of danger and can evacuate before the events
  • Better building designs can withstand earthquakes-> feel less at risk
59
Q

Iceland: context

A
  • Lies on the Mid Atlantic ridge: constructive plate margin through the middle of the Atlantic ocean
  • Several active volcanoes: eruption occurs on average every 5 years
  • Earthquakes are common
  • 350,000+ population, 2 million+ tourists
60
Q

Why do people living in Iceland feel tectonic activity doesn’t pose a threat?

A
  • Effective scientific monitoring
  • Awareness of potential dangers
  • Brings benefits to the country
61
Q

What benefits does tectonic activity bring to Iceland?

A
  • Hot water from earth’s crust provides 90% of buildings with heat and hot water
  • Volcanic rocks used in road + building construction
  • Landscape: waterfalls, volcanoes, glaciers-> huge tourism draw, providing jobs (2018- 70,000 jobs)
  • Eruption of Eyjafjallajokull in 2010 led to surge in tourism
  • Geothermal energy used to generate 27% of electricity
  • Natural hot water from earth crust used to heat greenhouses + swimming pools
62
Q

What are the 4 management strategies for reducing the risk of tectonic hazards?

A

Monitoring- using scientific equipment to detect warning signs of an event
Prediction- using historical evidence and monitoring, scientists make predictions about when and where tectonic hazards may happen
Protection- designing buildings that can withstand tectonic hazards
Planning- identifying and avoiding places most at risk

63
Q

What are the warning signs of a volcanic eruption?

A
  • Rocks fracture, rising magma causes earthquakes
  • sides of volcano swell as magma rises
  • heat melts snow (mountains)
  • gases from rising magma
  • water heated by magma causes steam eruptions
64
Q

How can Monitoring be used as a management strategy for volcanoes?

A
  • Seismographs to detect and record earthquakes
  • tiltometers to monitor ground deformation
  • gravity meters to measure change in density
  • instruments to monitor gas emissions and changes in water chemistry

Warnings issued is eruption seems likely-> evacuation

65
Q

How can Monitoring be used as a management strategy for earthquakes?

A

Japan:
- network of seismometers monitor and record earthquakes
- public warnings issues through TV and media
- seek immediate shelter, trains slow, factories halt production

  • Tsunami monitoring systems (pacific + indian ocean): floating buoys detect early tsunami waves after earthquakes
  • ## warnings issued to coastal areas-> tell people to seek higher ground
66
Q

How can Prediction be used as a management strategy for volcanoes?

A
  • Based on scientific monitoring
    Iceland:
  • 2010, increase in tectonic activity beneath Eyjafjallajokull icecap-> enabled scientists to make accurate prediction of the March and April eruptions that year
67
Q

How can Prediction be used as a management strategy for earthquakes?

A

Impossible to make accurate predictions-> lack of clear warning signs
- can study historical records of earthquakes at plate margins
- identify locations believed to be at greatest risk (ie Istanbul, Turkey)

68
Q

How can Protection be used as a management strategy for volcanoes?

A

Italy- attempts to use embankments to divert lava flow
Japan- control lahars (mudflows of ash and water) by building small dams

Can design buildings to withstand effects of volcanic ash (ash mixed with water, causes roof collapse)
- steep, smooth tiled roofs prevent build up of ash
- roofs less likely to fall with strong, lateral support
- Window shutters prevent ash entering homes

69
Q

How can Protection be used as a management strategy for earthquakes?

A

Effective way to reduce risk
- buildings, bridges and highways can be designed to withstand ground shaking
- Retrofitting: existing structures modified

Japan:
After 2011 tsunami-> built 400km seawall up to 12.5m high
Tokyo, Mori tower-> reinforced steel piping, motion absorbing oil dampers (absorb shockwaves, minimise shaking)

70
Q

How can Planning be used as a management strategy for volcanoes?

A

Hazard maps
- reduce risk, help protect people in danger
- use evidence from previous explosions, plot likely extent of hazards (ie ashfalls, pyroclastic falls, lahars)
- control development, plan evacuation routes

71
Q

How can Planning be used as a management strategy for earthquakes?

A

Shakemaps show impact of groundshaking
- planning authorities use-> locate high value developments (hospitals, power stations, office blocks) AWAY FROM high risk areas

ie after 1989 earthquake in San Fransisco, many houses have been rebuilt or retrofitted to withstand earthquakes

72
Q

What is Eyjafjallajokull?

A

A composite volcano (stratovolcano) completely covered by an ice cap
100km, feeds many outlet glaciers
Erupted between March-May 2010

73
Q

How does the location of Iceland affect Eyjafjallajokull?

A
  • Lies on mid-Atlantic ridge (constructive plate margin) between the North American plate and the Eurasian plate. They are moving apart due to ridge push
  • Plates move apart, magma fills multiple magma chamber below Eyjafjallajökull (produces significant amount)
74
Q

When were the Eruptions of Eyjafjallajokull in 2010?

A

March: Evacuation of around 500 people (mainly lava eruption)
April: (10-20x more powerful) Air traffic in Europe, cancellations of 1000’s of flights from Europe and Iceland due to ash in air

75
Q

What were the primary effects of Eyjafjallajokull erupting?

A
  • Light from sun blocked out by ash, face masks worn to prevent choking
  • Homes + roads damaged, services disrupted
  • Crops destroyed by ash, roads washed away
  • April 2010: Europe airspace standstill, costing billions of euros in delays. No fly zone during eruption (loss of £130m a day)
76
Q

What were the secondary effects of Eyjafjallajokull erupting?

A
  • Sporting events affected due to cancelled flights
  • Fresh food import stopped
  • Lack of raw materials imported (affect industries)
  • Local water contaminated with fluoride
  • Flooding caused as glacier melted
77
Q

What were the international effects of Eyjafjallajokull erupting?

A

Kenya: left with rotting fruit and flowers due to inability to export products into Europe, lost $1.3m every day

78
Q

What were the opportunities created from Eyjafjallajokull erupting?

A
  • Grounding of flights: prevented 2.8 million tonnes of CO2
  • Increase of passengers on Eurostar
  • Ash deposited iron into North America, triggering plankton boom- increasing biodiversity
79
Q

What were the strategies used to reduce impacts of eruptions in Iceland?

A

European Red Cross: provide food, resources, therapy, housing
EU- air traffic management

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