Tectonics

Tectonics

plate boundaries
1. types
  1. divergent/constructive
    1. rifts, new crust, volcanoes
  2. collision
    1. mountains
  3. conservative
    1. sliding opposite ways, earthquakes
  4. convergent/destructive
    1. subduction zone, mountains, volcanoes
2. subduction zone:
  1. 2 plates moving together, ocean subducted under continent
    1. fold mountains created & volcanoes & earthquakes
Earthquakes
1. normally along plate boundaries, often convergent & conservative
2. sudden movements, near surface, pre-exisitng faults.
3. gradual pressure buildup released.
  1. vibrations (waves)
    1. L waves (love waves) : surface - horizontal on surface
    2. S waves: slow - only solids
    3. P waves: fast - solid & liquids
    4. severity of earthquake based on amplitude.
    5. S & L waves most destructive. crustal fracturing & 3 secondary hazards.
      1. Liquefaction
        loose rocks & sediment affected. ground looses load bearing capacity.Large buildings settle in the ground / collapse
        (turns ground into liquid)
      2. Tsunamis
        earthquakes out to see/secondary impact.
      3. Landslides
        slopes weakened by seismic waves. ground slides due to gravity
    6. Rayleigh wave: surface of crust, rolling motion, responsible for most shaking felt by people.
4. hypocentre/focus
  1. point where pressure is released
5. epicentre
  1. on surface above hypocentre
6. Impacts
  1. vary
    1. over time
    2. from place to place
    3. nuisance to disaster
  2. usually far worse than volcanoes
  3. 5% of population likely to be affected
  4. factors
    1. speed of recovery (resilience)
    2. total number affected
    3. level of development & per capita GDP
    4. amount of uninsured losses
    5. level of urbanisation
volcanoes
1. around 500 active now.
  1. a lot in the ring of fire
2. near plate boundaries, also hotspots
  1. hot spots: middle of plates, fedfrom underlying magma, area of thin crust
    1. e.g. Hawaii
3. primary hazards:
  1. pyroclastic flows
    1. magma at the vent bubbles & burst, hot materials & poisonous gases roll down mountain sides
  2. Tephra (ash falls)
    1. rock fragments fired into atmosphere. sizes - boulders to dust. accumulate on roofs = building collapse, start fires.
  3. lava flows
    1. flows of molten rock, fast moving & lethal
  4. volcanic gases
    1. mixed gases released in explosion. CO2 very dangerous
4. secondary hazards:
  1. lahars
    1. mud flows, caused by heavy rain on slops & fine volcanic material
  2. jokulhaups
    1. floods caused by eruptions under glaciers.
5. impacts
  1. only small area directly damaged
  2. only 1% of world likely to suffer volcanic eruption
  3. factors
    1. level of development per capita GDP
    2. number affected
    3. speed of recovery (resilience)
    4. amount of uninsured losses
    5. level of urbanisation
6. lava types:
  1. basaltic lava
    1. 1000-1200 C, thin runny, gentle, ocean hot spots, mid ocean ridges, shield.
  2. andesitic lava
    1. 800-1000 C, slow, violent, moderately explosive, composite, subduction zones.
  3. rhyolitic lava
    1. 650-800 C, thick stiff, violent, super & composite volcanoes.
Tsunami
1. submarine shock waves
  1. from earthquakes/volcanoes
2. often around pacific coast
  1. gentle sloping shelf = great heights
3. most lethal secondary earthquake hazard.
4. no threat out to sea. only as land gets shallow they grow in height.
5. impact depends on:
  1. event duration
  2. wave amplitude & distance travelled
  3. depth & gradient of offshore zone
  4. coastal barriers
    1. mangroves
    2. headlands
    3. reefs.
    4. sand banks
    5. Cliffs
  5. day/night
  6. warning systems
  7. population density/ degree of developments on coast.
6. impacts
  1. factors
    1. level of development per capita GDP
    2. numbers affected
    3. speed of recovery (resilience)
    4. amount of uninsured losses
    5. level of urbanisation
theory: surface = 2 types of plates. thin crust underlying ocean & thick underlying continents. thick crust floats (less dense)
1. crust formed at divergent boundaries on sea floor
2. convection currents = movement
paleomagnetism
1. magma locking in earth's magnetic polarity, used to reconstruct plate movement
Hazards: natural events that threatens/causes injury & deaths, damage to property
Disasters: occur when hazards have significant impact on populations. hazard becomes disaster when 100+ die/affect.
1. Risk = (hazard x exposure x vulnerability) / manageability
Risk: exposure of people to hazards. relates to probability of a hazard leading to loss of life/lively hood.
1. difficult to assess, can include:
  1. individual/community perception
  2. unpredictability of hazard.
    1. people get caught out by timing/magnitude.
  3. lack of alternatives.
    1. people still live in hazard zones, lack of options, good farming
  4. benefits of living in area can out weigh negatives
  5. acceptance of risk
Vulnerability: how likely a community/structure is to suffer from a disaster.
resilience: ability for community to resist, absor & recover from a hazard.
Hazard Profiles
1. magnitude & intensity
  1. richter scale
    1. earthquake
    2. 0-9
    3. measures height of waves, absolute scale, will measure the same anywhere. 1 on scale = 10X
  2. Mercalli scale
    1. earthquake
    2. I-XII
    3. different amounts of shaking, based on damage & movement of goods
  3. Moment magnitude scale
    1. earthquake
    2. 0-9
    3. describes earthquake in terms of energy released. based on seismic movement, calculated by amount of slip in the fault. used by US Geological Survey for large earthquakes. 1 on scale = 10X
  4. volcanic explosivity index
    1. volcanoes
    2. 0-8
    3. measured from volume of products ejected. increase in 1 on scale = 10X
2. hazard profiles used to compare
3. understand the physical characteristic of hazards
4. earthquakes, volcanoes, tsunamis
development & governance
1. often correlates to vulnerability & resilience
2. economic development
  1. access to resources, organisations, technology
  2. higher income leads to living in safe locations/hazard proof areas.
3. education access
  1. aware of hazards/what to do
4. heathcare access
  1. better health
  2. resistance to disease
5. housing
  1. poor quality
    1. cant withstand hazards
6. governance
  1. way a country, city, community, company etc is run
  2. three concepts
    1. authority
    2. decision making
    3. accountability
  3. good governance embraces principles such as rule of law, transparency, equity, participation
  4. poor governance can be corrupt, weak both increase vulnerability
    1. failing to invest in infrastructure, warning systems
    2. ill prepared
  5. stakeholders: individuals, communities, organisations. governments, businesses with interest in situation (hazard risk)
geographical factors
1. population density
2. urbanisation: people, goods, businesses at risk
3. isolation/inaccessibility: hard to get help
4. community spirit: boost moral
contrasting locations
1. high development
  1. an handle better but more financial damage
2. low development
  1. rely on others, less to loose
management of the disasters & hazards
1. mega disaster
  1. large scale (area involved & economic, human impact)
  2. huge challenges, especially at emergency stage.
  3. substantial international aid
2. no universal definition for disaster
3. small events in remote locations often under/not recorded
4. disaster, death, damage often under recorded for political reasons
5. some parts are at risk of multiple hazards, locations with 3 overlapping hazards = hazard hot spot
  1. extremely disaster prone, more than one type of natural hazard
6. predicting
  1. volcanoes have some signs
  2. harder to predict earthquakes
    1. need to detect areas of tectonic stress
7. management cycle
  1. 3. reconstruction & mitigation
  2. 2. initial recovery (rehab)
  3. 1. emergency response
  4. 5. lesson learned, implement remedial actions
  5. 4. return to normal
  6. improving preparedness
8. mitigation & preparedness
  1. preparedness: educating people about what to do & improving warning system & equipment
  2. mitigation: action taken to reduce/eliminate risk to life & property in future
    1. often outcome of stage 5 and taken in stage 3
    2. referred to as adaptation
  3. 3 basic actions to mitigate the impacts
    1. modifying the hazard event
      1. no tech yet
      2. strengthening coastal defences
        tsunami
      3. diverting/chilling lava flows
      4. increasing slope stability
    2. modifying vulnerability and resilience
      1. improving prediction
        forecasting prediction, warning systems,
        scientific research, modern tech gives better warning systems.
      2. improving community preparedness
        enforcing building codes, especially public buildings.
      3. changing behaviours, moving people away from high risk zone
    3. modifying potential financial loss
      1. insurance
        insurance need to asses:
        level of risk
        probability of certain magnitude hazard
        market value of property to be insured
        likely cost of repair & reconstruction
      2. Disaster aid
        often during the emergency/early recovery
        donations from
        voluntary organisations & charities
        e.g. Red Cross
        governments to intergovernmental organisations
        e.g. UN
        often criticised as they can be inefficient or corrupt, does not encourage self help and bottom up management
9. response
  1. factors affecting response
    1. physical
      1. type of hazard
      2. topography of area
      3. climate
      4. accessability
    2. human
      1. scientific understanding
      2. level of community preparedness
      3. technology/engineering
      4. population density/number involved
      5. education & training
      6. economic wealth
      7. infrastructure
      8. government framework
  2. Parks response curve
    1. used to analyse timeline between hazard striking and return to normality
10. Sendai Framework
  1. 1. understand the disaster risk
  2. 2. ensure government strengthening to manage hazard risk
  3. 3. invest in improving resilience and disaster preparedness
  4. 4. 'build back better' in recovery
earth structure
1. inner core
  1. 7000 C
  2. very dense
  3. 80% iron 20% nickel
  4. solid
2. mantle
  1. 870 C
  2. medium to less dense
  3. upper = olivine lower = magnesium silicate
  4. phases of solid and liquid
3. crust
  1. 400 C
  2. less dense
  3. granite (continental) basalt (oceanic)
  4. solid
4. outer core
  1. 4400-6100 C
  2. dense
  3. 88% iron 12% sulphur
  4. liquid

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