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Geography IBDP > Hazards > Flashcards

Hazards Flashcards

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1
Q

What are the 5 layers of the Earth?

A
  • Crust
  • Upper Mantle
  • Lower Mantle
  • Outer Core
  • Inner Core
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2
Q

Describe how convection currents can lead to plate movements

A

The structure of the Earth contains 5 layers: the crust, the upper and lower mantle, the inner core and outer core. The mantle is full of magma and this is where convection currents occur. The cool, more dense magma sinks to the warmer, outer core. This heats up the magma which causes it to rise towards the crust. This magma is less dense so it rises up and cools as it is further away from the outer core. As it cools again, the magma becomes more dense and sinks. This cycle is repeated and these convection currents cause the tectonic plates in the earths crust to move.

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3
Q

What is Advection?

A

Advection is the transfer of heat by the flow of a fluid, especially horizontally.

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4
Q

Properties of Composite Volcanoes

A
  • Also known as Stratovolcanoes
  • Steep sided cones formed from alternating ash and lava flows
  • Pyroclastic flows rather than lava flows
  • Explosive upon eruption
  • -> Explosive due to thick, viscous lava
  • -> viscous lava can’t run as far, increasing the cone shape over time
  • Parasitic cones may grow on the side of the volcano
  • Can have several vents
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5
Q

Properties of Shield Volcanoes

A
  • Low, gently sloping sides
  • Formed from layers of lava
  • Typically non-explosive eruptions
  • Fast flowing lava
  • Frequent but gentle eruptions
  • Shallow crater
  • Larger circumference
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6
Q

Properties of Cinder Cone Volcanoes

A
  • Formerd from fragmets of solid material which accumulates as a steep conical hill around a vent, forming a cone
  • The shape usually depends on the nature of the material
  • Usually concave and the material spreads out near the base
  • Steep angle of 30º-40º
  • Violent eruptions with lava breaking up into cinders, ash and other fragments
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7
Q

Volcanic Hazards:

- Pyroclastic Flows and surges

A
  • Gravity driven
  • Can travel at speeds greater than 80km/h and can reach speeds of 400km/h
  • Mixture of rock fragments, ash and hot gasses
  • Can be at temperatures of up to 700ºC

Pyroclastic flows

  • Higher Density
  • confined to valleys

Pyroclastic surges:

  • lower density
  • can expand over hills and valleys
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8
Q

Volcanic Hazards:

- Lahars

A

A flow of debris consisting of pyroclastic material, water, rocks etc.

A more violent mudflow that flows down the sides of the volcano typically along a river valley

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9
Q

Volcanic Hazards:

- Tephra and Ballistic Projectiles

A

Fragmental material that are produced from the volcano upon eruption. They can be various sizes

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10
Q

Volcanic Hazards:

- Volcanic Gas

A
  • Water vapour
  • Carbon dioxide
  • Carbon monoxide
  • Sulfur oxides
  • Hydrogen sulfide
  • Chlorine
  • Fluorine
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11
Q

Volcanic Hazards:

- Tsunamis

A

Relatively infrequent but volcanic eruptions represent impulsive disturbances which can displace a great volume of water and generate destructive tsunami waves.

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12
Q

How are volcanoes formed?

A
  • Magma within the Earth’s upper mantle reaches the surface through a vent or fault in the tectonic plates
  • At the surface, it erupts to form lava flows and ash deposits
  • Lava solidifies
  • Over time the volcano continues to erupt, causing more lava to solidify, increasing the size of the volcano
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13
Q

Types of Lava Eruptions

A

Hawaiian:

  • Infrequent but violent eruptions
  • Lava in areas where oceanic and continental plates meet features silica-rich sediments. this causes the lava to become move viscous and block vents until enough pressure has built up to break them open

Icelandic:

  • Persistent fissure eruption
  • Large quantities of basaltic lava may build up on horizontal plains
  • occasional pyroclastic material occurs
  • runny lava and volcanic gases escape easily
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14
Q

Types of Pyroclastic Eruptions:

A

Strombolian:

  • explosive
  • pyroclastic rock
  • commonly marked by a white cloud of steam emitted form the crater

Vulcanian:

  • more violent
  • occur when the pressure of trapped gasses in viscous lava becomes sufficient to blow off the overlaying crust of solidified lava

Vesuvian:

  • powerful blasts of gas pushing ash clouds high into the sky
  • lava flow may occur

Plinian:

  • violent eruptions characterised by pulverised rock and ash clouds several km thick
  • gas clouds and lava can oc cur
  • part of the volcano may be blasted away during the eruption
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15
Q

Montserrat Volcano Case Study

- Mt Soufriere Hills

A
  • 18th July 1995
  • North & South American plate subduct under Caribbean plate

Primary Hazards:

  • 23 deaths
  • Over 100 people injured
  • Plymouth (capital) covered in ash and evacuated
  • High % of homes, businesses, infrastructure lost/destroyed
  • Main airport & port closed
  • 75% of the island was covered in Ash

Secondary Hazards:

  • Long time taken to rebuild homes & vital infrastructure
  • Ongoing respiratory problems & disease
  • Environmental damage to beaches, forests, wildlife and coral reefs
  • Population fell from 12,000 to 1,500 (1995-2001)
  • Skills shortage due to emigration
  • Fear of over-dependence on UK ‘handouts’

Impact on Wellbeing:

  • loss of loved ones
  • pressures on housing
  • loss of employment as businesses were forced to shut
  • skills shortage due to emigration

Varying levels of vulnerability:
Spatial variations in hazard perception:
- 75% of the island was covered in ash, forced migration to the North of the island
- People were given £2500 to relocate to the UK permanently

Personal Knowledge:

  • previous eruptions but deadliest in 1997
  • ongoing minor hazards such as lahars and tephra

Preparedness:

  • were not prepared for the eruption but now have permanents warning systems such as
  • -> seismic monitoring
  • -> deformation monitoring
  • -> environmental monitoring
  • -> volcano-logical monitoring
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16
Q

Indonesia Volcano Case Study

- Mt Sinnabung

A
  • 28th August 2010
  • Indo-Australian plate subducts under Eurasian plate

Primary Hazards:

  • 30,000 villagers evacuated from their homes
  • 2010 has 1 death, 2014 killed 16 and 2016 killed 7

Secondary Hazards:

  • 2013 has crops failing to grow due to ashfall
  • area around the volcano was extremely fertile

Impacts on Wellbeing:

  • people not allowed to move back into their homes
  • loss of loved ones
  • loss of jobs due to closed businesses

Varying levels of vulnerability:
Spatial variations:
- 2014 eruption occurred 5km away from a village who were just allowed t move back into their homes following previous eruptions

Personal Knowledge:
- 2014 was deadliest eruption but others still caused harm

Preparedness:
- Not prepared

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17
Q

What is an Earthquake?

A

A series of seismic vibrations or shock waves that originate from the focus

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18
Q

What is the Focus?

A

The point at which plates release tension or compression suddenly.

  • Shallow focus earthquakes occur relatively close to the ground surface
  • Deep focus earthquakes occur at considerable depth under the ground
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19
Q

What is the Epicentre?

A

The epicentre marks the point on the surface of the earth directly above the focus of the earthquake

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20
Q

Seismic Waves

- Description and Types

A

Seismic waves can travel along the surface of the earth and also through the body of the earth

There are body and surface waves.

  • Body waves are transmitted upwards and towards the surface from the focus of the earthquake.
  • Surface waves are produced in the ground by the transformation of some body waves once they reach the surface.

Body:

  • Primary (P) waves / pressure waves
  • Secondary (S) waves / shear waves

Surface:

  • Love waves
  • Rayleigh waves
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21
Q

Features of Seismic Waves

A 
Body Waves
P waves: 
- Fastest - 6.1km/s
- Travels through solids and liquids 
- Vertical shaking

S waves:

  • Slower - 4.1km/sec
  • Travels through solids
  • Horizontal shaking
Surface Waves
Love waves: 
- Slow
- Travels through solids - on the crust 
- Horizontal shaking 
Rayleigh waves: 
- Slow 
- Travels through solids - on the crust 
- Vertical shaking
22
Q

Properties of Primary and Secondary Waves (Body Waves)

A

Primary waves moves faster than secondary waves because they are compressional like sound waves. Compressing and expanding rock and liquid in the same direction in which they move. Once it reaches the surface it can also compress air which makes the explosion sound.

Secondary waves are more destructive than primary waves because buildings can not withstand much horizontal stress.
Surface waves cause the most amount of damage

23
Q

Human causes of earthquakes

A

Construction of large dams:

  • water pressure created in the micro-cracks in the ground near a reservoir
  • water pressure in rocks increases, lubricating faults

Mining

Hydraulic fracturing:
- rock is fractured by pressurised liquid injected into deep rock formations to fracture rocks

Testing on Nuclear Weapons:
- underground nuclear weapon testing has triggered earthquakes

24
Q

The Richter scale

A
  • Measures the magnitude of an earthquake
  • Logarithmic scale from 1-10 with 5 being 10 times more powerful than 4
  • Magnitudes of above 7 are less frequent but very powerful and destructive
25
Q

Earthquake primary hazards

A
  • shaking
  • grond ruptures
  • landslides
  • collapsed buildings
  • burst water and gas lines
  • fissures in roads and pavements
26
Q

Earthquake secondary hazards

A
  • aftershocks
  • fires
  • disease from water contamination
  • blocked roads
  • dam disturbances
  • floods
  • tsunamis
  • soil liquefaction
27
Q

Earthquake warning signs

A
  • Observing unusual changes in animal behaviour
  • Possible foreshocks
  • Investigate the seismic cycle of any faults in the area
  • Check an earthquake tracking website
  • rising levels of groundwater
  • increased amounts of radon in water sources
28
Q

Haiti Earthquake case study

- Port-au-Prince

A
  • 12th January 2010 16:53
  • 13km deep focus
  • Epicentre 25km west of Port-Au-Prince
  • 7.0 magnitude
  • 1/3 of the population impacted

Primary Hazards:

  • 230,000 people killed
  • 300,000 injuries
  • Several hospitals collapsed
  • Main airport, most ports and infrastructure damaged
  • 294,383 homes damaged
  • Damaged communication infrastructure

Secondary Hazards:

  • Businesses destroyed
  • Job losses
  • Rebuilding infrastructure has taken many years
  • people still living in temporary accommodation
  • increase in diseases eg cholera

Impact on wellbeing:

  • loss of homes and loved ones
  • unemployment and isolated people due to damage

Varying levels of Vulnerability:
Spatial variations:
- People in Port-Au-Prince affected due to dense population and poor building codes on housing
- people living on steeper terrains vulnerable due to unstable ground

Personal knowledge:
- knowledge hindered as its an LIC & people are less educated

Preparedness:

  • many of the 2 million people living in Port-Au-Prince had moves of tin roofed shacks on unstable, steep ravines.
  • 60% of the buildings were unstable under normal conditions
29
Q

New Zealand Earthquake case study

- Christchurch

A
  • 22nd Feb 2011 12:51
  • 5km deep focus
  • Epicentre 10km South East of Christchurch
  • 6.3 magnitude
  • aftershock of 2010 e-quake

Primary Hazards:

  • 183 people killed
  • 2000 people injured
  • 50% of city’s buildings damaged
  • 80% of city had no electricity
  • Part of the largest glacier broke apart (Franz Josef glacier)

Secondary Hazards:

  • loss of jobs and income due to closed businesses
  • damaged to roads from liquefaction, making it hard for emergency services to get through
  • Loss of tourism

Impact on Wellbeing:

  • unemployed people due to business closures
  • loss of loved ones and homes

Varying levels of vulnerability
Spatial variations:
- occurred at noon so people were out
- close to centre of Christchurch

Personal Knowledge:

  • more than 10,000 e-quakes have hit Christchurch prior to 2011 so people are used to them
  • larger recurrence interval

Preparedness:

  • most residents live in securely built homes or apartments on flatter land
  • 18% of households met basic preparations involving 3 days of food & water supply for household
  • better preparation by securing tall and heavy furniture down
30
Q

Mass Movements

- Characteristics of rockfall

A
  • Rock falls in chunks but acts like a liquid

- Occur in dry or semi-arid climates and are common when drought is broken by heavy rainfall

31
Q

Mass Movements

- Characteristics of mudflow

A
  • high level of acting like a liquid in comparison to rockfall
  • soils rich in clay, little rain and not much vegetation to hold the soil in place along with high precipitation will create a mudflow
  • they usually occur during times of rainfall or volcanic eruptions
32
Q

Mass Movements

- Soil Creep

A
  • generally occurs after rainfall
  • slow movement that happens over a long period of time
  • seasonal
  • progressive, slopes are reaching the point of failure as other types of mass movements
  • Usually occurs during or after rainfall

Indicated by curved tree trunks, bent fences or retaining walls

33
Q

Mass Movements

- Slumping

A
  • More of the land acts like a liquid
  • slow and long process
  • can be dangerous and lead to the destruction of houses and key infrastructure
  • slumping can move from meters per second to meters per year
34
Q

Constructive (Divergent) Plate Boundary

A
  • Both earthquakes and volcanoes can occur
  • convection currents in the mantle push the plates apart/away from each other
  • this exposes magma to the surface and cools, forming rock
  • an example is the Mid Atlantic Ridge and it has also led to the formation of Iceland (middle of North American and Eurasian plate boundary)
35
Q

Destructive (Convergent) Plate Boundary

A
  • Both earthquakes and volcanoes can occur
  • the convection currents in the mantle push the oceanic and continental plates towards each other
  • the denser, oceanic plate subducts underneath the continental plate
  • the crust melts in the mantle, pushing the magma up to the earth’s surface which erupts as magma
  • Eg Nazca plate subducting underneath the South American plate
36
Q

Collision (Convergent) Plate Boundary:

A
  • Earthquakes occur but volcanoes do not
  • The convection currents in the mantle push 2 continental plates together
  • one plate subducts under the other
  • fold mountains are created by 2 plates being pushed together
  • Eg Himalayas formed from Indo-Australian and Eurasian plate
37
Q

Conservative (Passive) Plate Boundary

A
  • Earthquakes occur
  • one plate moves faster than the other plate
  • pressure build up and causes earthquakes to occur
  • Eg San Andreas Fault involving North American Plate and Juan De Fuca plate
38
Q

Hotspots

A
  • it happens mid-plate
  • a plume of magma finds a weakness and can erupt and form land
  • as the plate moves, new land is created as more magma reaches the surface
  • Eg Hawaii
39
Q

What is a recurrence interval/period?

A

the expected frequency of occurrence in years for an event of a particular size

40
Q

What does the Moment Magnitude Scale measure?

A

The amount of energy released from an earthquake.

41
Q

What is the Volcanic Explosive Index

A

The strength of a volcano is measured by the Volcanic Explosive Index. This is based on the amount of material ejected in the explosion, the height of the cloud it creates and the amount of damage caused.

42
Q

Environmental Hazards

- What is a behavioural school of thought

A
  • It considers that environmental hazards are the result of natural events. People put themselves at risk by (eg). living on or at the foot of steep slopes. People are more at risk because they are close to the hazard event
43
Q

Environmental Hazards

- What is a structuralist school of thought

A
  • It stresses the constraints placed upon poor people by the prevailing social and political system of the country. Poor people live in unsafe areas such as on steep slopes or floodplains because they are preventing from living in better areas
44
Q

How can economic factors make people more vulnerable to hazards?

A
  • Countries with a higher GDP should be able to afford to construct buildings that can withstand natural hazards
  • Countries with a higher GDP can afford warning systems so the population can evacuate if necessary
45
Q

How can demographic factors increase vulnerability to hazards?

A

If a country has an ageing population and are in a vulnerable area, this can be a large risk which leads to making people more vulnerable as it is more difficult to get them to safety.

46
Q

Factors Affecting the Impact of Hazards

A
  • Magnitude
  • Frequency
  • Distance from the event
  • Time of day
  • Population Density
  • Economic Development
  • Building type
  • Type of rock and sediments
  • Secondary Hazards
47
Q

What is a supervolcano?

A

A large volcano that has the potential to erupt which then affects the global climate and ecosystem

48
Q

What is Vulnerability?

A

Vulnerability is the characteristics and circumstances of community, system or asset that make it susceptible to the impacts of a hazard

Is the factors that affect the susceptibility of a community to the effects of hazard events

49
Q

Factors affecting vulnerability

A

Physical Factors:

  • poor design and construction of buildings
  • unregulated land use

Social Factors:

  • poverty and inequality
  • social discrimination by gender, social status, disability and age

Economic Factors:

  • areas that are dependent on a single industry
  • people working in the informal sector

Environmental Factors:

  • poor environment management
  • over-consumption of natural resources
50
Q

What is Risk?

A

Risk is the consequence of the interaction between a hazard and the characteristics that make people vulnerable

51
Q

Sectors that can manage the risk

A

The Insurance Sector
- Insurance firms may be able to recover disaster losses

The Construction Sector
- Buildings are built according to building codes and regulations

The Land-Use and Urban Planning Sector
- location of new developments take into account the likelihood of a hazard event

At Community Level
- an understanding of hazard events can influence decisions on preparedness, including evacuation procedures

Disaster risk management can reduce risk reduction , conducted by doing:

  • Prevention - the avoidance of adverse impacts
  • Mitigation - the reduction of advert impacts of hazards
  • Preparedness - the knowledge and capacities of interested parties
52
Q

Mass Movements Case Study

- Kalimpong, West Bengal, India

A

Event Profile: Landslide

  • Occurred at the end of the dry season
  • Kalimpong is at a height of 1250m
  • Water was discharged down the dry gullies and the flanks of the channel were unstable

Primary Hazards

  • construction of terraced houses on the slopes increased the steepness behind the house, making the slope more unstable
  • slopes become extremely hazardous every monsoon system however they cannot blast the slopes to be rid of the instability due to

Geography IBDP (8 decks)

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