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Natural Disasters Part 1 (Plate Tectonics (History of the Theory…

- - - - State/State Disaster
        
        U.S. Government/National Disaster.
  - - - Prevent damage by various means
      - Increase the response to disasters
      - Mitigation Approaches
        
        Controlled events like fires and avalanches
        
        Redirecting the event with dams, Dikes and levees
        
        Modifying structures to withstand damage like earthquakes
        
        Regulating hazardous areas
  - - - Good
        
        Increase Construction Jobs
        
        Able to upgrade destroed buildings
        
        Grants to stimulate growth
        
        Increase data to predict with
        
        more resources for the rest of us
      - Bad
        
        Major Relocation
        
        Loss of resources
        
        Reduces output
        
        If physical decrease, but human stays the same per capita wealth decreases.
- - - - Evidence of the reversal of the magnetic field
        
        Variations of the magnetic pull from rocks on the sea floor
        
        Paleomagnetists: scientists of the ancient magnetic field of the earth
        
        Two types of rocks
        
        Normal Polarity: same polarity of present day magnetic field
        
        Reversed Polarity: what it implies
        
        Magnetite can sync up to the magnetic field
        
        When magma cools the polarity is looked in
        
        Polarity of rock in strips parallel to the ridge
      - Discovery that the ocean floor recycles and spreads
        
        Seafloor Spreading
        
        At the ridge the rocks are young and get older the farther away you get.
        
        the youngest rocks have normal polarity
        
        the polarity has flipped several times
        
        Hess and Dietz coined the name seafloor spreading
        
        Recycle Ocean Crust
        
        New Crust at ridge. Old is eaten at the trenches
        
        Trenches along the rim of the pacific
        
        Hess: the Atlantic growing Pacific shrinking.
      - Ruggedness and youth of the ocean floor
        
        Before 19th c. the ocean was believed to be flat
        
        WWI echo-sounding device used to discover the ruggedness and tech. accelerated in WWII.
        
        mid-Atlantic ridge is the most prominent feature of earth
        
        1947 ship Atlantis found that the sediment layer was thinner than they thought, much thinner.
        
        Global Mid-ocean ridge: 50,000 kilometers long/ sometime 800km across/ sometimes 4500km above the sea floor.
      - earthquakes along sea trenches and mountains
        
        "Benioff Zones"
        
        earthquake zones parallel to trenches
        
        Subduction Zones
        
        Where there are concentrations of earthquakes
  - - - Divergent
        
        spreading Centers = sea ridges
        
        New Crust
        
        Baseltic, Non-BOOM Volcano
        
        Sallow low power earthquake
      - Convergent
        
        Reverse or thrust fault
        
        = Subduction Zone
        
        Oceanic-continental Convergence
        
        Island arc: Hawaii
        
        Continental-continental Convergence: Himalayan Mt.
        
        Shallow but wide earthquakes that make land hazardous
      - Transform
        
        They slid past eachother
        
        "Fracture Zones
        
        Connect Two similar plates mostly divergent
        
        100-1000+ long and >8 km deep
      - Unknown
        
        have complicated geological
        structures and earthquake patterns.
        
        Microplates and larger plates mashed together
        
        an indistinct, or diffuse, plate
        boundary
    - - Magnetic stripping Polarity of the ocean floor. calculate the age of the rock and you find the average time and rate the plates move at.
      - Geology Mapping?
      - Geodesy is the science of the size and shape of the Earth.
      - The three most commonly used space-geodetic techniques -- very long baseline interferometry (VLBI), satellite laser
        ranging (SLR), and the Global Positioning System (GPS)
      - By repeatedly measuring distances between specific points, geologists can determine if there has been active movement along faults or between plates.
  - - - Radioactive decay
      - Residual heat
  - - - Crust
      - Mantle
      - Core
    - - Lithosphere
        
        = Crust and the top layer
      - Asthenosphere
        
        "Plastic"