Lecture2 systems


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Lecture2 systems

  1. 1. Announcements Please turn in Quiz #1 Math review, Mon. & Weds. 4-4:45 pm, in McG-S 230
  2. 2. The Tools of Geography <ul><li>maps </li></ul><ul><li>GIS </li></ul><ul><li>remote sensing </li></ul><ul><li>statistics </li></ul><ul><li>numerical models </li></ul><ul><li>LOGIC! </li></ul>Which object best approximates the shape of the Earth? Frisbee Beachball
  3. 5. <ul><li>Not only did the ancient Greeks know the Earth was round, Eratosthenes estimated its diameter within 1% of actual size in 200 BC! </li></ul><ul><li>Columbus wasn’t such a rebel after all. </li></ul>
  4. 7. 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
  5. 8. 6378.16 km
  6. 9. 6378.16 km 6356.8 km
  7. 10. The 4 Spheres of Geography
  8. 11. Lithosphere Hydrosphere Atmosphere Biosphere
  9. 12. Lithosphere Hydrosphere Atmosphere Biosphere
  10. 13. Lithosphere Hydrosphere Atmosphere Biosphere Soil
  11. 14. Systems <ul><li>An ordered, interrelated set of “ things ” & their “ attributes ” </li></ul><ul><li>linked by “ flows ” of energy and/or matter </li></ul>thing 1 thing 2 flow
  12. 15. Systems <ul><li>Systems thinking is vital for all the observational sciences... </li></ul><ul><li>We can’t run experiments big enough! </li></ul><ul><li>Examples of Systems: </li></ul><ul><li>Ecosystem </li></ul><ul><li>River Channel </li></ul><ul><li>Weather </li></ul><ul><li>Plate Tectonics </li></ul>
  13. 16. 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?
  14. 17. Open Systems <ul><li>Matter or energy flows in and out </li></ul>Input Output e.g., Crim Dell
  15. 19. Open Systems <ul><li>Systems can be in </li></ul><ul><li>equilibrium (inputs = outputs) </li></ul><ul><li>or disequilibrium (inputs ≠ outputs) </li></ul>Input Output e.g., Crim Dell
  16. 20. Open Systems <ul><li>If Crim Dell is in equilibrium, storage stays constant: Steady State </li></ul><ul><li>What does this mean for the water level through time? It is stable. </li></ul>Add 500 gallons per week Lose 500 gallons per week Input Output e.g., Crim Dell
  17. 21. Open Systems <ul><li>If there is a drought and inflow is reduced, what would you expect to happen? </li></ul><ul><li>To outflow? </li></ul><ul><li>To storage? </li></ul>Add 200 gallons per week Lose ??? gallons per week ??? Input Output e.g., Crim Dell
  18. 22. <ul><li>Open </li></ul>Closed input output <ul><li>inputs and/or outputs of energy or matter in a system </li></ul><ul><li>no inputs or outputs </li></ul><ul><li>matter/energy moves endlessly in series of interconnected paths </li></ul><ul><li>= CYCLES </li></ul>Closed Systems
  19. 23. Closed Systems <ul><li>Whether a system is open or closed depends on scale . </li></ul><ul><li>Scales range from: </li></ul><ul><li>local regional global universal </li></ul><ul><li>If we expand the frame of reference to a global scale , most Earth systems become closed ; we live on a finite planet </li></ul><ul><li>Examples? Exceptions? </li></ul>
  20. 24. Closed Systems <ul><li>Examples of closed systems: </li></ul><ul><li>Rock cycle </li></ul><ul><li>Water cycle </li></ul><ul><li>Food web* </li></ul><ul><li>Carbon cycle </li></ul><ul><li>* If you include death and decay… </li></ul>(Lithosphere) (Hydrosphere) (Biosphere) (All four!)
  21. 25. Closed Systems <ul><li>Exception: </li></ul>Solar Inputs Radiation output to space Energy
  22. 26. Energy as a System <ul><li>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. </li></ul>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.
  23. 27. 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