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A Level Geography > Tectonic Hazards > Flashcards

Tectonic Hazards Flashcards

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1
Q

What are the 2 types of tectonic plate?

A

Continental

Oceanic

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2
Q

What is the asthenosphere?

A

Part of the mantle below the lithosphere where the rock is semi molten.

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3
Q

What are the different processes that affect plate movement?

A

Mantle convection.

Slab pull

Subduction

Sea floor spreading

Paleomagnetism.

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4
Q

What is mantle convection?

A

Heat produced by the decay of radioactive elements in Earths core heat the lower mantle and creates convection currents.

Hot liquid magna currents thought too be in circles in the asthenosphere thus causing the plates to move - now less accepted.

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5
Q

What is slab pull?

A

Newly formed oceanic crust at mid ocean ridges become denser and thicker as it cools.
This causes it to sink into the mantle underneath its own weight pulling the rest of the plate down with it.
Increasingly seen as a major factor in plate movement.

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6
Q

What is subduction?

A

Plate destruction.
As two oceanic plates or an oceanic and continental plate move towards eachother one slides under the other into the mantle where it melts into the subduction zone.

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7
Q

What is sea floor spreading?

A

Process of new crust pushing tectonic plates apart. In middle of oceans there are mid ocean ridges or underwater mountain ranges which form when hot magma is forced up from the asthenosphere and gardens forming new oceanic crust.

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8
Q

What is paleomagnetism?

A

Confirmed sea floor spreading. Every 400,000 years the earths magnetic fields change direction. When lava cools and becomes rock, minerals inside the rock line up with the Earths magnetic direction (polarity) at the time.

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9
Q

What is a plate boundary?

A

Where 2 tectonic plates meet.

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10
Q

What are the 3 types of plate boundary?

A

Convergent
Divergent
Conservative

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11
Q

What is a convergent plate boundary also known as?

A

Destructive margins

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12
Q

What is a divergent plate boundary also known as?

A

Constructive margin

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13
Q

What is a conservative boundary also known as?

A

Transform margin.

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14
Q

Explain divergent plate boundaries.

A

Two plates are moving apart (diverging) leading to formation of new crust.
In oceans this divergence forms mid ocean ridges and on continents it forms rift valleys.

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15
Q

Name example of mode ocean ridge

A

Mid Atlantic ridge

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16
Q

Describe the tectonic hazards at mid ocean ridges?

A

Earthquakes are shallow focus and occur frequently, pose little threat to humans as they are small and underwater.

Volcanoes, submarine volcanoes can occur some one which can be above sea level to form new islands, eg Iceland on mid Atlantic ridge. Generally less explosive and more effusive:

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17
Q

What does effusive mean?

A

A type of eruption where lava steadily flows out of a volcano.

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18
Q

How does a Rift Valley form?

A

Continental plates move apart the crust stretches and breaks into sets of parallel cracks (faults). The land between these faults then collapses forming steep sided rift valleys

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19
Q

Name example of Rift Valley?

A

East African Rift Valley.

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20
Q

Describe tectonic hazards at rift valleys?

A

Earthquakes, similar to mid ocean ridges, shallow and low magnitude

Volcanoes- don’t occur here as magma never reaches the surface.

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21
Q

What is the subduction zone?

A

Broad areas where two plate are moving together. Often thinner more dense oceanic plate descends beneath the continental plate.

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22
Q

What is a locked fault?

A

In a subduction zone as plates move together they can get stuck due to frictional resistance. These faults may store strain for extended periods, eventually released in a large magnitude earthquake.

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23
Q

What is the Benioff zone?

A

An area of seismicity corresponding with the slab bearing thrust downwards into a subduction zone where the pressure is released form locked fault.

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24
Q

Explain how an earthquake occurs at subduction zone?

A

Two plates collide, heaviest plate sinks (oceanic) at the subduction zone. Plates do not slide smoothly over eachother, they create friction. Frictional resistance causes a locked fault to form where the plates get stuck. Energy is stored here and builds up, finally in the Benioff zone, the frictional pressure is released causing an earthquake.

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25
Q

What forms when the oceanic plate subducts?

A

The continental plate folds and is pushed upwards forming fold mountains. Caused by melting of oceanic plate in asthenosphere, molten rocks rise to the surface of mantle and release out of fold mountains.

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26
Q

Which plate subducts where oceanic meets oceanic?

A

Either the faster moving one

Ore the one with the largest crust.

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27
Q

Explain what happens when oceanic meets oceanic?

A

Subducts plate melts and magma rises to form under water volcanoes. Over millions of years these grow above sea level to form island volcanoes called island arcs.

Earthquakes often occur, often shallow to deep and can be very powerful

Tsunamis also occur.

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28
Q

What forms when continental meets continental?

A

A collision margin forms.

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29
Q

Explain what happens when a continental plate meets a continental plate?

A

Both plates have same density and these plates are less dense than the asthenosphere, neither plate is subducted. Instead these plates collide and the sediments between them are crumpled and forced up to form high fold mountains.

Any earthquakes that occur here are shallow.

Eg Himalayas.

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30
Q

What happens at conservative plate margin?

A

Two plates are sliding past eachother resulting in major breaks in the crust between them as they move.

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31
Q

What are earthquakes like at conservative plate margins?

A

Big and powerful earthquakes as there is no subduction, no Benioff zone. The earthquakes are shallow and result from friction between the two plates.

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32
Q

Example of conservative plate margin?

A

San Andreas Fault

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33
Q

What is the focus / hypocentre?

A

The point inside the crust from which the pressure is released.

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34
Q

What is the epicentre?

A

The point on Earths surface that is directly above the focus / hypocentre.

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35
Q

What are the 3 types of seismic wave?

A

Primary P waves

Secondary S waves

Love L waves

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36
Q

Describe primary P waves

A

Body waves - travel through earths body

Fastest and first to reach the surface (8km/sec)

Travel through solids and liquids

Move backwards and forwards (left to right)

Only damaging in most powerful earthquakes

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37
Q

Describe secondary S waves?

A

Also body waves - travel through earths body

Slower than P waves (4km / sec)

Only travel through solids.

Move up and down in motion perpendicular to direction of travel

Do more damage than P waves.

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38
Q

Describe Love L waves?

A

Surface waves only travel on earths surface

Slowest if 3 waves, last to arrive

Move side to side motion, perpendicular to direction of travel.

Larger and do the most damage

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39
Q

What does the overall severity of an earthquake depend on?

A

Links to the amplitude and the frequency of the wave types.

Ground surface may be displaced horizontally, vertically or obliquely (slanted) during an earthquake

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40
Q

How can you predict earthquakes?

A

Cannot be predicted.
Can us epilate boundary knowledge to forecast where an earthquake is likely to happen, eg areas that have had large earthquakes before

Research focuses on precursors which may indicate an earthquake is going to happen eg Foreshocks

41
Q

What physical factors affect the impact of an earthquake?

A

Magnitude

Depth

Distance from epicentre

Geology (soft rocks amplify shaking)

42
Q

What human factors impact effect of earthquakes?

A

Level of development

Population

Levels of preparation

Effectiveness of emergency response

Impact of secondary hazards

43
Q

What are primary effects of earthquakes?

A

Ground shaking causing buildings etc to collapse

Crustal fracturing - when Earths crust cracks due to the energy that is released.

44
Q

What are secondary effects of earthquakes?

A

Landslides or avalanches

Tsunamis

Liquefaction : where surface rocks lose strength and become more liquid than solid. Buildings sink into the ‘soil’

45
Q

What are the primary hazards from volcanic eruptions?

A

Lava flows

Pyroclastic flows

Tephra and Ash Falls

Gas Eruptions

46
Q

What are lava flows?

A

Streams of lava flowing across earths surface
Can reach 1170 degrees C and take years to cool fully, destiny everything in their path.

Generally not the eating as they move slowly so people can move out of the way.

47
Q

What are pyroclastic flows?

A

Mix of dense hot rock ash lava and gases ejected from volcano. Can each 700 degrees C

Move up to 100mk/h

Destroy everything in path

48
Q

What is tephra and Ash falls?

A

Tephra are pieces of volcanic rock that blast into the air during eruptions.

Large pieces fall near to volcano where they cause injury / death as well as structural damage; and ash can travel for thousands of kilometres.

Ash fall causes disruption through poor visibility, slippery roads. Roots can collapse under weight a d engines can get clogged up with Ash

49
Q

What are gas eruptions?

A

Magna contains dissolved gases that are released into the air during eruptions.
Gases include water vapour, carbon dioxide and sulphur dioxide.
Once gases are in the air they can travel for thousands of kilometres.
Gases can be harmful and hazardous to people animals and structures

50
Q

What are the secondary hazards of volcanic eruptions?

A

Lahars

Jökulhlaup

51
Q

What are Lahars?

A

Masses of rock mud and water that travel quickly down the sides of volcano and they vary in size and speed.

Caused when eruptions quickly melts snow or ice or when heavy rainfall has occurred either during or after an eruption.

52
Q

What are jökulhlaup?

A

Glacial outburst floods.
Occur when heat of volcano melts the snow and ice of a glacier causing heavy and sudden floods.

These occur suddenly and release large amounts of water rocks and ice that can be very dangerous as they flood and damage land and structures.

53
Q

Can you predict volcanic eruptions?

A

Use gps and satellite based radar placed in and around volcanoes to monitor the signs

Monitoring of small earthquakes, changes to the surface of volcano and changes to the tilt of a volcano can indicate that an eruption is about to occur.

54
Q

How are most tsunamis caused?

A

Underwater earthquakes, some caused by underwater landslides.
Energy released during the earthquake causes the sea floor to uplift, displacing the water columns.

55
Q

Explain how a tsunami occurs?

A

Tsunami forms in deep ocean, difficult to detect, long wavelength and short in height.

Water column rises as the ocean gets shallower (towards land)

The nature / size of the wave depends on the cause, distance travelled from source, water depth on route and the topography of the shoreline.

The depth and destruction of the tsunami depends on the land use, population, and the level of warnings given.

56
Q

How to predict tsunamis?

A

Very hard to predict.

Early warning can be possible due to signals and DART monitoring etc

57
Q

How are tsunamis monitored?

A

Early warning systems in place.
Use seismic detectors to detect submarine earthquakes, and additional equipment also used eg

DART used sea bed detectors and surface buoys to monitor changes in sea level and pressure.

When waves detected the into is sent to scientists via satellite where the data can be analysed and the correct people can be informed if necessary.

58
Q

Pros and cons of computer modelling for monitoring tsunamis?

A

Can save lives

Info can reviewed regularly due to multiple sensors / buoys

Cons:
Faulty equipment can result in inaccurate data
Shallow earthquakes can damage equipment

59
Q

What is hazard?

A

A percieved natural / geophysical event that had the potential to threaten both life and property

60
Q

What is a disaster?

A

The realisation of a hazard when it causes a significant impact on the vulnerable population,

61
Q

When does a hazard become a disaster according to CRED?

A

When 10 or more people are killed

100 or more people are affected.

62
Q

What is the formular for Hazard Risk?

A

Risk(R) = Hazard (H) x Vulnerability(V)
———————————————-
Capacity to Cope

63
Q

What is resilience?

A

The ability to protect lives, livelihoods and infrastructure from destruction and to restore areas after a natural hazard has occurred.

64
Q

How can you increases resilience?

A

Improving infrastructure

Monitoring systems

Warning systems

65
Q

What political factors effect vulnerability to hazards?

A

Existence and enforcement of building codes and regs

Efficiency of emergency services and response teams

Existence of public education and practices hazard responses

Corruption levels

Existence of disaster preparedness plans

Quality of infrastructure

66
Q

What social factors impact vulnerability?

A

People without access to education

Poor quality housing

Communities with poor health and healthcare

Age of a population

67
Q

What environmental factors impact levels of vulnerability?

A

Accessibility of an area

Rapid urbanisation increases demand for housing

Areas with high population density have poorer quality housing

68
Q

What does the pressure and release model show?

A

The progression of vulnerability through the root causes which lead up to unsafe conditions in the event of a hazard or disaster

69
Q

How can you measure tectonic hazards?

A

Richter Scale

Mércalli Scale

Moment Magnitude Scale (MMS)

Volcanic Explosivity Index

70
Q

What does the Richter scale measure?

A

Measures the amplitude of the waves produced by an earthquake.

71
Q

What does the MMS measure?

A

Describes the event in terms of the energy released. Based on the seismic moment which is calculated from the amount of slip of the fault, the area affected and and Earth rigidity factor.

72
Q

What does the Mercalli Scale Measure?

A

Measures the experienced impacts of an earthquake on a scale of I - XII (Roman numerals)

Relative scale, not fact based.

73
Q

What does the volcanic explosivity index measure?

A

A relative measure of explosiveness of a volcanic eruption which is calculated from the volume of the products, height of the eruption cloud and also qualitative observations.

74
Q

Advantages of hazard profiling?

A

Can be used to compare hazards

Simple

Easy to compare / make comparisons

Help governments to develop disaster plans

Can show multiple hazards.

75
Q

Disadvantages of hazard profiling?

A

Non specific

Subjective = lost reliability

76
Q

What is a multiple hazard zone?

A

Places where a number of physical hazards combine to create an increased level of risk for the country and its population.

77
Q

Example of MHZ?

A

The Philippines

78
Q

What is the hazard management cycle?

A

Covers 4 areas; mitigation, preparedness, response and recovery, which can be used by governments to protect people from natural hazards that threaten their communities.

Useful as cycle involves all key players, and all key factors that can reduce impact so effective use SHOULD manage the impact.

79
Q

What does parks model show?

A

Shows how a country or region may respond after a hazard event.

Can be used to compare how areas at different levels of development mug he recover from a hazard event.

Analyses the response to a disaster with a time scale
Shows responses - improvements or not
Shows how time can change quality of life.

Can compare different events in different countries and the differing impacts of the event and can help governments to plan for the future.

80
Q

What are theoretical frameworks?

A

Models that governments and organisations can use to predict, reduce the impact and manage situations in the event of a natural disaster.

81
Q

Examples of theoretical frameworks?

A

Predictions of tectonic hazards using DART or sensory equipment etc

Hazard response curve - Parks Model

Hazard Management cycle

82
Q

What are hazard mitigation strategies?

A

Meant to avoid, delay or prevent hazard events

83
Q

What are hazard adaption strategies?

A

Strategies designed to reduce the impact of hazard events

84
Q

Give examples of hazard mitigation strategies for tectonic events?

A

Land Use Zoning

Diverting Lava Flows

GIS Mapping

Hazard Resistant Design and Engineering Defences

85
Q

How can land use zoning reduce, delay or prevent impacts of disaster?

A

Protects people and property

Land divided into zones dependent on risks. Areas at high risk will be under strict regulations. Settlements limited if allowed at all, communities may be resettled in a safer place, certain building types / structure prohibited as they may pose danger in event.

86
Q

How do diverting lava flows work?

A

Building barriers and digging channels to divert lava flows in directions away from causing harm.

Fairly ineffective because path taken by lava difficult to predict.

Terrain has to be suitable

Saving one community may put others in danger.

87
Q

How does GIS mapping work to mitigate risk?

A

Identifies where evacuation routes should be placed.

Can show areas worst affected by hazards

The locations of airports and airstrips etc

Locations and rough population sizes of major towns / cities

Helps direct aid where it’s needed most and find nearest drop off locations etc

88
Q

How is hazard resistant design useful at mitigation?

A

New buildings can be built to resist ground shaking and therefore will not collapse

Roofs build near volcanoes can be sloped so ash slides off them rather then building up in the roof

Buildings at risk from tsunami can be built well above sea level.

Existing buildings can be modified.

Protective structures like sea walls can be built

Generally expensive but work well and there are cheaper alternatives that work similarly.

89
Q

Name some examples of hazard adaption strategies?

A

High tech monitoring

Crisis mapping

Modelling hazard impact

Public education.

90
Q

Explain high tech monitoring

A

Early warning systems

Satellite communication technologies

Mobile phone warnings technology - eg in Japan

91
Q

How does crisis mapping work?

A

Uses crowd sourced information as well as setllite technology and maps to accurately map areas struck by disaster

Pre mapping the vulnerable areas helps to get aid responses there rapidly in the event of disaster.

92
Q

Modelling hazard impacts what is it?

A

Computer modelling allows scientists to predict the impact of hazard events on communities. Info is fed into computer systems and then model the effects of a disaster and preparation plans can be put into place.

93
Q

What does public education involve?

A

Teaching evacuation routes
What to do in event of earthquakes etc
Creation of emergency preparedness kits in schools and workplaces

Regularly practicing emergency procedures.

94
Q

Who are the key players in the response to natural disasters?

A

Aid donors

NGO’s

Insurance Companies

Communities

95
Q

What role does aid play in the response to natural disasters?

A

Emergency aid
Short term aid
Long term aid

Provided as cash personnel or services
Reconstruction or providing food or temporary shelters

+ helps massively

  • prone to corruption
  • can create dependency in long term
96
Q

What role do NGO’a play?

A

Important to disasters where local governments find it difficult to respond - no money or funds

Providing shelters food helping with reconstruction
Re-establishing water supplies etc

Providing funds and co-ordinate search and rescue efforts and also help to develop reconstruction plans

  • lead to dependency
  • doesn’t always reach the most rural areas
97
Q

What role does insurance play in responses to hazards?

A

Insurance coverage can help communities to recover from disasters providing individuals and businesses with the money they need to rebuild their lives
Costs can be covered by groupings of insurance companies.

  • not everyone has insurance
  • insurance very rare in developing countries
  • government and bank partnerships do not occur in developing countries so there is little support.
98
Q

What role do communities play in the response to a disaster?

A

Crucial to search and rescue efforts

In remote or isolated communities aid may not reach them for days/weeks so villagers undertake the responsibilities themselves, saving lives etc

First in the scene

Community groups heavily involved in long term strategies for rebuilding

  • little financial backing
  • less impact than aid etc
  • requires support from others.

A Level Geography (12 decks)

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