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Eduqas GCSE Geology (9-1) > 4.1 Earth Hazards and their Mitigation > Flashcards

4.1 Earth Hazards and their Mitigation Flashcards

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1
Q

What are the earth hazards you need to know about for this course?

A
  • earthquakes
  • tsunamis
  • landslides
  • volcanoes
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2
Q

What can landslides also be known as?

A

Mass movement

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3
Q

What is seismology?

A

The study of earthquakes

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4
Q

What are the different types of earthquake wave - in order of speed (most to least)?

A
  1. P waves
  2. S waves
  3. surface waves
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5
Q

Which type of earthquake wave causes the most damage?

A

Secondary

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6
Q

What is the Richter Scale measured by?

A

The ground shaking caused by the earthquake

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7
Q

What is tectonic unzipping?

A

A series of earthquakes along an active fault (over hundreds of years)

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8
Q

Why do earthquakes occur in San Francisco?

A

Due to being on the San Andreas Fault

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9
Q

Why does liquefaction occur?

A

Due to the shaking in wet sediments, which separates the grains and makes them behave like quicksand

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10
Q

What can be triggered by earthquakes?

A

Landslips and tsunamis

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11
Q

What effect will a high population density have on the death toll?

A

Increase death toll

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12
Q

How does the wealth of a country affect how disastrous an earthquake would be?

A

Wealthy country - better prepared but greater economic loss/property damage

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13
Q

What methods can be used to predict earthquakes?

A
  • seismic gaps
  • hazard maps
  • changes in ground levels
  • gas measurements
  • changes in water levels in wells
  • foreshocks
  • animal behaviour
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14
Q

How can seismic gaps help to predict earthquakes?

A
  • if area along fault has regular tremors then stress is being released - so large earthquake unlikely
  • area has few tremors - stress building - could result in big earthquake
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15
Q

How can hazard maps help to predict earthquakes?

A

Maps show places most likely to suffer from major earthquakes to focus attention on areas most in need

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16
Q

How can changes in ground levels help to predict earthquakes?

A

Area around focus of earthquake may tilt due to swelling

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17
Q

What equipment can show change in ground levels due to earthquakes?

A

Tiltmeters and lasers

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18
Q

How can gas measurements help to predict earthquakes?

A

Radon, radioactive gas, moves up through cracks and can be detected in water in wells - if it ↑ then it shows rock is cracking more than usual = earthquake

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19
Q

How can changes in water levels in wells help to predict earthquakes?

A

If rocks are cracking, groundwater will sink into cracks and water levels fall

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20
Q

How can foreshocks help to predict earthquakes?

A

Number of foreshocks increases before a major events

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21
Q

How can animal behaviour help to predict earthquakes?

A

Some animals show disturbed behaviour before events - may be due to slight changes in earth’s magnetic field

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22
Q

How can the risk from earthquakes be reduced?

A
  • planning
  • building design
  • ground or base isolation systems
  • resisting shear forces
  • absorbing sway
  • services
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23
Q

Features of a shield volcano?

A
  • basalt
  • less viscous
  • less gas within - so runny
  • 1200 *C
  • lava flow, ash, small tephra
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24
Q

Features of a composite volcano?

A
  • andesite and rhyolite
  • more viscous
  • explosive - lava and pyroclastic flow
  • huge tephra
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25
Q

Where do basaltic volcanoes form?

A

Along constructive boundaries above hot spots

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26
Q

Where do andesitic volcanoes form?

A

Above subduction zones

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27
Q

What type of volcano is more likely to cause major problems?

A

Explosive andesitic variety

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28
Q

What are some volcanic hazards?

A
  • lava flow
  • ash
  • pyroclastic flow
  • gas
  • lahar
  • lateral blast
29
Q

Description of lava flow?

A

Localised distribution, depending on viscosity, and more dangerous to property than life

30
Q

Description of ash?

A

Widespread and a health hazard to living things - cause roof collapse and destruction of farmland

31
Q

Description of pyroclastic flow?

A

Local to volcano - very destructive and extreme hazard to life, given their temps and high velocity

32
Q

Description of lahar?

A

Also known as volcanic mudflows - destructive in vicinity of volcano - particularly in tropical areas with heavy rainfall

33
Q

Description of lateral blast?

A

Dangerous locally when volcano collapses and erupts sideways → fan shape of destruction

34
Q

Why do volcanoes not warm the climate?

A
  • if anything, they cool it
  • produce ash - condensation nuclei
  • form clouds → high albeido
35
Q

What does VEI stand for?

A

Volcanic explosivity index

36
Q

What is the VEI?

A

Relative measure of the explosiveness of volcanic eruptions - measured by volume of material erupted - each VEI is 10x larger than the one below

37
Q

What methods can be used to predict volcanic eruptions?

A
  • patterns of activity
  • ground deformation
  • gas emissions
  • groundwater changes
38
Q

How can ground deformation help to predict volcanic eruptions?

A

Tiltmeters and GPR can be used to measure changes in volcano’s size/slope angle - swelling volcano suggests magma moving closer to surface

39
Q

How can gas emissions help to predict volcanic eruptions?

A

As magma nears surface and pressure ↓, gases escape - ↑ amounts of SiO2 suggest magma near surface

40
Q

How can groundwater changes help to predict volcanic eruptions?

A

↑ pressure causes water levels to rise and suddenly drop - ↑ heat flow can reduce flow in aquifers

41
Q

How can the risks of volcanic eruptions be reduced?

A

Hazards maps

42
Q

How can hazard maps help reduce risks of volcanic eruptions?

A
  • used by public officials
  • create plans for evacuation, rescue and recovery
  • future land use planning can be based on hazard maps
43
Q

What was the major tsunami in 2011?

A

Japanese tsunami, 2011

44
Q

What is a tsunami?

A

A water wave that occurs at the same time as an earthquake, but it is not a seismic wave

45
Q

What is a tsunami caused by?

A
  • the bodily displacement of a large volume of water by the movement of a large section of crust on the sea floor
  • also due to the displacement of water by large landslides
46
Q

In open water, what is the approximate amplitude of a tsunami?

A

A meter

47
Q

In open water, what is the approximate wavelength of a tsunami?

A

Several hundred km

48
Q

In open water, what is the approximate speed of a tsunami?

A

Up to 700 km/h

49
Q

What happens when a tsunami approaches the shallow waters of the coast?

A

The height of the wave increases dramatically, surging across low-lying coastal areas

50
Q

What is the result of tsunamis?

A
  • buildings swept away
  • people die - especially in low lying areas
  • contaminated groundwater supplies
  • damage to land near coast - reduce crop yield
  • natural environment suffers
51
Q

Prediction methods for which natural disaster are similar to that of tsunamis? Why is this?

A

Earthquakes as most tsunamis result from earthquakes

52
Q

How can risks from tsunamis be reduced?

A
  • good early warning system - earthquake usually arrives well before tsunami - giving several hours warning for distant epicentres
  • Indian Ocean Tsunami Warning System - set up by UNESCO
53
Q

How do raised coastal roads reduce effects of tsunamis?

A

Allows for easier evacuation

54
Q

How do embankments reduce effects of tsunamis?

A

Acts as a barrier to water moving inland

55
Q

How do buildings at right angles to the coast set on concrete piles reduce effects of tsunamis?

A

Keeps property above the height of the water

56
Q

How do development-free zones of parks and forests reduce effects of tsunamis?

A

Slows down the water without damaging property

57
Q

What are landslides?

A

Sudden movements of masses of rock and soil that may affect areas covering many square kilometers

58
Q

What are the main types of landslides?

A
  • translational
  • topple
  • creep
  • rotational
  • fall
  • flow
59
Q

What are the factors that will influence whether a landslide is likely or not?

A
  • ROCK TYPE - strength, porosity and permeability, geological structures e.g. faults, weathering
  • SLOPE ANGLE - clay unstable at 10° whereas other rocks can form vertical slopes
  • WATER - heavy rainfall = lubricant
  • PEOPLE
60
Q

What will be the final cause of a landslide?

A

Heavy rainfall

61
Q

Which human activities can increase the chance that a landslide might happen?

A
  • adding weight by building on slope
  • removing material from base of slope
  • pipes leaking water and sewage
  • removal of vegetation
  • tarmac
62
Q

What is geomorphology?

A

Nature of the landscape

63
Q

How might glacial erosion 20,000 years prior contributed to a landslide?

A

Boulder clay formed which is easily eroded

64
Q

What is used to gather landslide characteristics?

A

Before and after aerial photographs

65
Q

What are the most effective methods of reducing the risk from landslides?

A
  • planning regulations controlling location of buildings
  • building codes to stabilise slopes
  • control drainage
  • reducing the load of overlying materials
  • reducing gradients of slopes
  • planting vegetation
  • filling permeable rock with cement
  • increasing insurance premiums on property to stop building homes in high risk areas
66
Q

In general, what methods of prediction are used for natural hazards?

A
  • hazard interval patterns (seismic gaps)
  • ground deformation (tiltmeters)
  • groundwater changes
  • gas emissions
67
Q

In general, what methods of reducing risk are there for natural hazards?

A
  • building design and regulation
  • prediction
  • warning schemes and evacuation
68
Q

What is the difference between lava flow and pyroclastic flow?

A

Lava flows are molten rock; pyroclastic flows are rock fragments, dust, ash and gases

Eduqas GCSE Geology (9-1) (13 decks)

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