Lecture2 systems
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Lecture2 systems






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Lecture2 systems Lecture2 systems Presentation Transcript

  • Announcements Please turn in Quiz #1 Math review, Mon. & Weds. 4-4:45 pm, in McG-S 230
  • The Tools of Geography
    • maps
    • GIS
    • remote sensing
    • statistics
    • numerical models
    • LOGIC!
    Which object best approximates the shape of the Earth? Frisbee Beachball
    • Not only did the ancient Greeks know the Earth was round, Eratosthenes estimated its diameter within 1% of actual size in 200 BC!
    • Columbus wasn’t such a rebel after all.
  • Sun Aswan Alexandria 7.2 ° Circ. = 2 π r Circumference = 805 km ∙ 50 805 km Circ. = 40,250 km r = 6400 km 7.2 ° 1 50 r = Circ. 2 π = 7.2° 360° 805 km Circumference = 1 50
  • 6378.16 km
  • 6378.16 km 6356.8 km
  • The 4 Spheres of Geography
  • Lithosphere Hydrosphere Atmosphere Biosphere
  • Lithosphere Hydrosphere Atmosphere Biosphere
  • Lithosphere Hydrosphere Atmosphere Biosphere Soil
  • Systems
    • An ordered, interrelated set of “ things ” & their “ attributes ”
    • linked by “ flows ” of energy and/or matter
    thing 1 thing 2 flow
  • Systems
    • Systems thinking is vital for all the observational sciences...
    • We can’t run experiments big enough!
    • Examples of Systems:
    • Ecosystem
    • River Channel
    • Weather
    • Plate Tectonics
  • Systems A systems approach to Earth’s energy balance From: Strahler & Strahler Where and how does the energy flow in this global-scale natural system?
  • Open Systems
    • Matter or energy flows in and out
    Input Output e.g., Crim Dell
  • Open Systems
    • Systems can be in
    • equilibrium (inputs = outputs)
    • or disequilibrium (inputs ≠ outputs)
    Input Output e.g., Crim Dell
  • Open Systems
    • If Crim Dell is in equilibrium, storage stays constant: Steady State
    • What does this mean for the water level through time? It is stable.
    Add 500 gallons per week Lose 500 gallons per week Input Output e.g., Crim Dell
  • Open Systems
    • If there is a drought and inflow is reduced, what would you expect to happen?
    • To outflow?
    • To storage?
    Add 200 gallons per week Lose ??? gallons per week ??? Input Output e.g., Crim Dell
    • Open
    Closed input output
    • inputs and/or outputs of energy or matter in a system
    • no inputs or outputs
    • matter/energy moves endlessly in series of interconnected paths
    • = CYCLES
    Closed Systems
  • Closed Systems
    • Whether a system is open or closed depends on scale .
    • Scales range from:
    • local regional global universal
    • If we expand the frame of reference to a global scale , most Earth systems become closed ; we live on a finite planet
    • Examples? Exceptions?
  • Closed Systems
    • Examples of closed systems:
    • Rock cycle
    • Water cycle
    • Food web*
    • Carbon cycle
    • * If you include death and decay…
    (Lithosphere) (Hydrosphere) (Biosphere) (All four!)
  • Closed Systems
    • Exception:
    Solar Inputs Radiation output to space Energy
  • Energy as a System
    • Used by Lord Kelvin to estimate the age of the Earth in 1863 (first extra-Biblical estimate): Given an initial temperature and a present temperature, we know the rate of heat loss, so can calculate an age.
    Energy on Earth is not quite in equilibrium 2 nd Law of Thermodynamics: Heat flows from warmer bodies (Earth) to cooler bodies (Space) Led to a huge conflict with Darwin et al. His age: 20-100 million years; not enough time for evolution or some observed geological phenomena.
  • Energy as a System But a scientist’s results are only as good as the data and the assumptions. What did Kelvin not know about? Convection in the mantle Heat from the radioactive decay of atomic nuclei