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Tectonics > Tectonics > Flashcards

Tectonics Flashcards

1
Q

Hazard risk equation

A

Risk = Event x Vulnerability
—————————
Capacity to cope

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2
Q

Natural hazard vs disaster (events)

A

Hazard = potential threat to people / property

Disaster = losses experienced & harm caused (impact on community)

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3
Q

What’s important / needed for resilience

A

Vulnerability & community threshold (capacity to cope)

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4
Q

Types of vulnerability

A
  • physical (hazard prone area, physical barriers)
  • economic (losing jobs/incomes)
  • social (DWAGES - disadvantaged / most vulnerable)
  • knowledge (lack training & education /religion & beliefs may limit understanding)
  • environment (high population density in risky areas)
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5
Q

Resilience definition

Factors of resilience

A

How well a population can recover from a disaster

  • metabolic flows (supply/consumption chains)
  • governance networks (institutional structures / organisations)
  • social dynamics (demographics, inequity)
  • built environment (ecosystem services)
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6
Q

How to build resilience

A
  • good international relationships
  • good governance
  • thorough training / awareness
  • pre-planned conversations
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7
Q

Scales used to measure magnitude & intensity of tectonic hazards

A
  • Mercalli = measures intensity of shaking produced by earthquake
  • Moment Magnitude Scale (MMS) = measures earthquake magnitude based on seismic movement
  • Volcanic Explosivity Index (VEI) = measures explosiveness of volcanic eruptions
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8
Q

The Pressure and Release Model (PAR)

A

Used to analyse factors which cause vulnerability (inter-relationships between hazards & wider context)

  • root causes
  • dynamic pressures
  • unsafe conditions
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9
Q

Root causes

A

Economic, demographic and political processes which affect large populations or entire country

  • weak governance
  • mismanagement of industry
  • high reliance on products/industries easily affected by hazards
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10
Q

Dynamic pressures

A

Local economic or political factors that can affect a community or organisation

Due to:

  • lack of basic services (health, education, police)
  • lack of training & education for locals
  • poor communication between gov & locales
  • rapid urbanisation
  • deforestation
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11
Q

Unsafe conditions

A

Physical conditions that affect an individual

  • informal settlements
  • lack of health & safety
  • poor education
  • poor infrastructure (electricity, sewage removal)
  • unsafe building (disease/fire can spread easily)
  • low income

(Kashmir)

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12
Q

Park model disaster response curve

A

Graphical representation of human responses to hazards

  • steepness of curve shows how quickly an area deteriorates & recovers
  • depth of curve shows scale of disaster

(More developed - less steep on deterioration, more steep on recovery & less deep)

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13
Q

Stages of Park model

A

Stage 1 - pre-disaster (modify cause & event)
Stage 2 - Relief (immediate local response - medial aid, search & rescue, appeal for foreign aid)
Stage 3 - Rehabilitation (foreign aid, modify the loss - temporary housing / services, food & water distributed)
Stage 4 - reconstruction (permanent rebuilding of physical & social infrastructure, reduce vulnerability to prevent further disasters (mitigation))

(Christchurch EQ, New Zealand)

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14
Q

Earth internal structure

A
  • inner core = solid due to extreme pressures & high temp: produced by radioactive decay
  • outer core = semi-molten rocks containing iron & nickel alloys, flows to create magnetic field
  • mantle = semi-molten, temp gradient towards core creates convection currents - may contribute to lithosphere plate tectonic movement
    asthenosphere = weakest part of upper mantle, lies beneath lithosphere
  • crust (Lithosphere) = thinnest, least dense & lightest layer of earth we live on made up of tectonic plates, oceanic crust a lot thinner than continental crust
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15
Q

Mantle convection

A
  • mantle heated from below (core)
  • in areas that are hotter it rises upwards (closer to core), area that are cooler sink down (near lithosphere)
  • results in convection currents in mantle
  • produces horizontal motion of mantle material close to Earth’s surface
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16
Q

Types for plate boundaries

A
  • Destructive = move towards each other (earthquakes, volcanoes, ocean trenches)
  • Constructive = away from each other (earthquakes, volcanoes, rift valleys, ocean ridges)
  • Conservative = slide past each other in same direction at different speeds or opposite direction (friction overcome & plates slip past in sudden movement, shockwaves produce EQ)
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17
Q

What occurs at constructive plate boundaries

A
  • sea floor spreading (paleo magnetism)

- ridge push & slap pull

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18
Q

Sea-floor spreading & paleo magnetism

A

Paleo magnetism = study of past changes in earth magnetic field, reverses every 200,000 years

  • tectonic plates split apart from each other as magnetic field reverses & new rock comes from underneath
  • as a result of mantle convection (less dense material rises, forming mountain/elevated area of sea floor)
  • creates mid ocean ridges between 2 oceanic plates / rift valleys between 2 continental plates
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19
Q

Ridge push & slab pull

A
  • driving force of plate tectonics
  • mid-ocean ridges fall away under gravity, pushes plates further apart, widening the gap
  • as plate is pulled at other end by gravity fed subduction, sinks into mantle
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20
Q

Volcano primary & secondary hazards

A

Primary hazards:

  • lava flows
  • pyroclastic flows
  • ash falls
  • gas eruptions

Secondary hazards:

  • lahars
  • jokulhlaup

(Mt Nyiragorgo in republic of Congo)

21
Q

Lava flows

A
  • molten magma flows on earth surface
  • viscosity determined by amount of silicon dioxide
  • buildings burnt / covered
22
Q

Pyroclastic flows

A
  • frothing bubbles of molten magma in volcano vent
  • volcano bursts explosively to eject dense mixture of hot gases & pyroclastic material (glass shard, pumice, crystals, ash)
  • can reach up to 1000C
  • moves rapidly down volcano
  • everything destroyed
  • leaves behind volcanic deposits (up to 200m thick)
  • causes floods (secondary hazards)
23
Q

Ash falls (tephra)

A

most ash fall locally

  • roof collapse
  • choke machinery/electronics
  • ppl/animal breathing difficulties
  • bury crops & vegetation
  • disrupts flight paths of planes
24
Q

Lahars

A

Water mixed with volcanic deposits flows rapidly along existing valley
- caused by heavy rainfall from volcanic ash / volcano water vapour

25
Q

Jokulhlaup (glacial run)

A

Glacial outburst floods

  • where water accumulates in subglacial lake beneath glacier
  • breaches damn & drains
26
Q

Strategies to modify an event (reduce risks)

A
  • land use zoning (keep residential/commercial areas away)
  • engineering defences (sea walls, mangroves)
  • diversion of lava flows (use seawater to solidify lava)
  • hazard resistant designs (retrofit/aseismic buildings)
27
Q

Tsunamis

A

result of sea bed & large water column displacement

  • caused by sub-marine earthquakes at subduction zones, earthquakes movement causes seabed to thrust up = displaces water
  • volcanic eruptions eject material into sea = displaces water
  • landslides cause land to fall into sea = large quantities of water displaced

displaced water becomes tsunami waves as waves reach shallower water in coastal areas = waves become higher

Shallower water = friction between tsunami waves & seabed increases, tsunami wave slows down = decreased wavelength but increased wave height

28
Q

Subduction zone

A

Where dense oceanic crust descends under less dense crust and melts into mantle at Benioff zone
destructive plate boundary

29
Q

Shield volcanoes

A
  • at constructive plate boundary (diverging)
  • lower silicates & gas content in magma
  • continuous eruption
  • calmer eruption
  • runny basaltic lava
  • gentle slope & short volcano
30
Q

Composite volcanoes

A
  • at destructive plate boundaries (subduction)
  • higher silicates & gas content in magma
  • longer dormancy (less frequent eruptions = pressure builds up = explosive eruption)
  • viscous (thick) andesitic lava
  • steep slopes & tall
31
Q

Landslide stresses

A
  • angle of slope
  • rainwater/saturation (encourages soil movement)
  • vibration (less consolidated area)
  • cliff erosion (creates stealer slope & less stable rock)
32
Q

Landslide strengths

A
  • less lubricant layers
  • tree/vegetation roots (bind soil together)
  • more consolidated material (rock type = less likely to move)
  • porosity of soil (less permeable = more surface run off = less saturated so stronger)
33
Q

Hydrometeorological hazards

A
  • floods
  • droughts
  • hurricanes
  • tornadoes
  • landslides

Caused by extreme meteorological/climate events

34
Q

Stages of hazard management cycle

A

Response (protection, evacuation, close transport)
Recovery (insurance, political alliances, scientists)
Mitigation (land use zoning, healthcare services, rebuilding)
Preparedness (evacuation, training, land use zoning)

35
Q

Earthquake waves primary & secondary hazards

A

Primary:

  • ground shacking (infrastructure collapses)
  • crustal fracturing (energy released causes crust to crack)

Secondary:

  • liquefaction (surface rocks shake violently & become liquid, lose ability to support building foundations)
  • landslides (violent shaking creates stress)
36
Q

What influences vulnerability & resilience

Development/social

A

Inequality of access to

  • education
  • housing
  • healthcare
  • income opportunities

(DWAGES)

37
Q

What influences vulnerability & community resilience

Geographic

A

governance

geographic factors

  • population density
  • isolation
  • accessibility
  • degree of urbanisation
38
Q

Strategies to modify (change) vulnerability & resilience

A
  • education (drills, training)
  • high tech monitoring (sensors, computer models)
  • community preparedness (towns work together, prepare alert systems)
  • adaptation (EOC, seismic retrofits: pump stations, police stations)
  • models forecasting disaster impacts
  • prediction (early warning systems)
39
Q

Strategies to modify loss

A
  • emergency aid (navy, volunteers, EOC)
  • short term / long term aid (charities, insurance companies)
  • insurance (insurers/NGOs)
  • actions of affected communities
40
Q

Hot spots

A

Cause intra-plate volcanoes/earthquakes

  • mantle plumes occur at areas where heat rises
  • high heat/low pressure at base of lithosphere = rock melts
  • magma rises & volcano formed
  • volcanoes move away as tectonic plates move over hotspot which remains stationary
  • volcanic island formed
41
Q

Hazard profile (definition & aspects)

A

Compares all physical process to help decision makers identify, rank hazards & decide how to allocate resources

  • magnitude
  • speed of onset
  • duration
  • areal extent
  • spatial predictability
  • frequency
42
Q

Global distribution of volcanoes

A
  • majority at destructive plate boundaries - melting magma at subduction zones, rend to be more violent
  • pacific, dominated by subduction zones = lots of volcanoes
  • some at constructive plate boundaries, plates pull apart & magma rises - less violent
  • none at conservative plate boundaries
  • hot spots cause intra-plate volcanoes eg. Hawaii, mantle plumes create mid plate eruptions
43
Q

Earthquake waves:

A

P waves

  • short wavelength
  • travel fast through solid & liquid
  • waves push & pull in direction of travel = creates compression & extension zones

S waves

  • longer wavelength
  • slower waves
  • only moves through solid rock
  • move at 90 to direction of travel

L waves

  • longest wavelength
  • slowest waves
  • only move at surface
  • most destructive waves
  • largest amplitude
  • shake ground from side to side as travels
44
Q

Types of natural hazards

A

Geophysical hazard

  • earthquake
  • volcano
  • landslide

(Hydro)Meteorological hazard:

  • cyclones
  • hurricanes
  • typhoons

Hydrological hazard:

  • tsunami
  • drought
  • flood
  • avalanche
45
Q

Why might more powerful hazards not cause the most deaths in some regions

A
  • better transport links (aid arrives faster, decreases injuries becoming fatalities)
  • richer / more developed (better infrastructure, aseismic buildings decrease deaths)
  • lower population density (fewer people exposed to hazards, less chance of being trapped by collapsing buildings or landslides)
46
Q

Why have the no. of reported hazards increased

A
  • increased no. of recording stations = more detected in remote areas
  • higher population density = more reporting (migration)
  • more reliable & accurate detection equipment tech (smaller magnitude earthquakes detected)
  • greater variety & coverage of media
47
Q

How do insurance losses differ in developed countries

A

Developed countries have more financial vulnerability (high value of insured property)

Eg. USA = large population size (310 million) &high GDP = high value residential properties in Florida around San Andreas fault

48
Q

Why no. of people affected by tectonic disasters have increased

A
  • global population growth
  • increased urbanisation = increased density
  • many of poor live in vulnerable shanty towns unprotected from hazards
  • improved incomes = more travel for leisure / business (people go to risky locations)
  • increased economic development = gov & cities can invest in adaptation strategies (ppl live in vulnerable locations which may be damaged)

Tectonics (3 decks)

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