lecture2 systems
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 Which object best approximates the approximates the
shape of the Earth?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
150
Aswan
Alexandria
7.2°
Circ. = 2 π r
Circumference = 805 km ∙ 50
805 km
Circ. = 40,250 km
r = 6400 km
r = Circ.2π
= 7.2°360°
805 kmCircumference
= 150
7.2°
6378.16 km6378.16 km
6378.16 km6378.16 km6356
.8 k
m63
56.8
km
The 4 Spheres of Geography
Lithosphere
HydrosphereAtmosphere
Biosphere
Lithosphere
HydrosphereAtmosphere
Biosphere
Lithosp
here
Hydro
spher
eAtmosphere
Biosphere
Soil
Systems
An ordered, interrelated set of “things” & their “attributes”
linked by “flows” of energy and/or matter
thing 1thing 1
thing 2thing 2
flowflow
Systems
Systems thinking is vital for all the observational sciences...We can’t run experiments big enough!
Examples of Systems:EcosystemRiver ChannelWeatherPlate 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 SystemsSystems can be in
equilibrium (inputs = outputs)
or disequilibrium (inputs ≠ outputs)
Input Output
e.g., Crim Dell
Open SystemsIf 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 SystemsIf 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 SystemsWhether 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 SystemsException:
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
2nd 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