Earth - Prof. Lloyd's Home Page
Transcript of Earth - Prof. Lloyd's Home Page
Universe 1
Astronomy 20 1
EarthThere's no place like home.
Astronomy 20 2
Earth
Earth as a planet
Largest terrestrialplanet
Magnetic field Plate tectonics Near inner edge of
Habitable Zone Uniquely placed for life
Astronomy 20 3
Earth
Internal Structure
liquid
solid
Universe 2
Astronomy 20 4
Earth
Magnetic Field
Generated by currents in outer core Field flips at irregular intervals
—about every million yrs Protects us from solar wind
Astronomy 20 5
Earth
Surface Geology
Continents vs ocean basinsOceansErosion by water and icePlate tectonics
Astronomy 20 6
Earth
Plate tectonics Continental & oceanic plates Volcanos & earthquakes on plate boundaries
Universe 3
Astronomy 20 7
Earth
Plate Boundaries
Mid-ocean ridges: sea-floorspreading
Subduction zones: destruction ofsea floor
Astronomy 20 8
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San Andreas Fault
Astronomy 20 9
Earth
Continental Drift World
continent:Pangaea
Atlantic oceanyoung
Universe 4
Astronomy 20 10
Earth
Atmosphere
Pressure = 1 bar
CompositionNitrogen 78%Oxygen 21%Argon 1%Water vapor 1-3%Carbon dioxide 0.03%
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Astronomy 20 11
Earth
History
Microscopic life
Fish
DinosaursMammals & birds
First bacteria
4500 Myr
540 Myr
250 Myr65 Myr
O2
No O2 K-T extinction
Astronomy 20 12
Earth
Faint Young Sun Paradox
Sun only 75% as bright inthe beginning.
Oceans should have beenfrozen till 2 Gyr ago.
Oldest sedimentary rocks3.8 Gyr old.
Resolution: CO2 →greenhouse effect
Universe 5
Astronomy 20 13
Earth
Continuously Habitable Zone
Problem: CO2 must have gonedown in a precise way.
Hart: CHZ very narrow0.95 AU – 1.01 AU
Implication: habitable planetsare rare.
Astronomy 20 14
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CO2 Cycle
Volcanos add CO2
Rain removes CO2
Astronomy 20 15
Earth
CO2 Thermostat
Rising temperature →More evaporation →More rainfall →Depletion of CO2 →Less greenhouse effect →Lower temperature
Universe 6
Astronomy 20 16
Earth
Continuously Habitable Zone
CO2 Thermostat → CHZ is wide
0.95 AU to 1.5 AU Habitable planets are common
Astronomy 20 17
Earth
Goldilocks & the 3 Planets
Mars: slowing of volcanic activity →loss of CO2 atmosphere
Venus: runaway greenhouse effect Earth: just right — barely!
Pika
What a close call!
Astronomy 20 18
Earth
The Far Future
Sun continues to brighten CO2 levels decline 900 Myr from now, too little CO2 for
plants →end of life on Earth 1700 Myr from now, T reaches
boiling → Earth ends up like Venus!