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# Lecture2 systems

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• 1. Announcements Please turn in Quiz #1 Math review, Mon. & Weds. 4-4:45 pm, in McG-S 230
• 2. The Tools of Geography
• maps
• GIS
• remote sensing
• statistics
• numerical models
• LOGIC!
Which object best approximates the shape of the Earth? Frisbee Beachball
• 3.
• 4.
• 5.
• 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.
• 6.
• 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
• 8. 6378.16 km
• 9. 6378.16 km 6356.8 km
• 10. The 4 Spheres of Geography
• 11. Lithosphere Hydrosphere Atmosphere Biosphere
• 12. Lithosphere Hydrosphere Atmosphere Biosphere
• 13. Lithosphere Hydrosphere Atmosphere Biosphere Soil
• 14. Systems
• An ordered, interrelated set of “ things ” & their “ attributes ”
• linked by “ flows ” of energy and/or matter
thing 1 thing 2 flow
• 15. 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
• 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?
• 17. Open Systems
• Matter or energy flows in and out
Input Output e.g., Crim Dell
• 18.
• 19. Open Systems
• Systems can be in
• equilibrium (inputs = outputs)
• or disequilibrium (inputs ≠ outputs)
Input Output e.g., Crim Dell
• 20. 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
• 21. 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
• 22.
• 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
• 23. 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?
• 24. 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!)
• 25. Closed Systems
• Exception:
Solar Inputs Radiation output to space Energy
• 26. 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.
• 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