Title: Lecture 5: Plate Tectonics and Climate Last 550 Myr (chapter 4)
1Lecture 5 Plate Tectonics and ClimateLast
550 Myr (chapter 4)
2Atmospheric CO2 Evolution
3Plate Tectonics Alfred Wegener (1914, German
Meteorologist) proposed continental drift
1-10 cm/yr gt5000km/100myr
Soft? acts as viscous fluid allows the tectonic
plates above to move
4Formation of the continents
- Sea floor spreading
- creation/destructoin of ocean crust
- since 175 myr
- Continental magnetic field
- reconstruct continental positions (lat.)
- since 550 myr
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6Paleomagnetic determination of past location of
continents the position of basalt rocks on (older
than 175 myr)
compass pointing vertical
compass pointing horizontal
7Paleomagnetic dating of ocean crust
Magnetic reversal (over land) and magnetic
lineations (in ocean)
8Moving Continents
Gondwana and S. P. Glaciation
100 Myr ago Cretaceous
Pangaea and Supermonsoon
200 Myr ago
9The Polar Position Hypothesis for alternative
icehouse and greenhouse climate
Glaciation occurs near polar position, But polar
postion does NOT guarantee glaciation
What else?
10Atmospheric CO2 Evolution
11Tectonic Control of CO2 Removal
Uplift-Weathering Hypothesis Marueen
Raymo et al., 1980s
Uplifting gt create fresh rock and mineral
surfaces gtstronger weathering gt reduce CO2
12The magic of breaking up
13Quantifying weathering rate with time
100
1
- Why fresh rocks has a much higher weathering rate
(over 100 times) - Fresh rocks has more weathering materials
fresh, unweathered silicates - Fragmentation increases surface area
14Uplift and chemical weathering
15Atmospheric CO2 Evolution
16Tectonic control of CO2 BLAG spreading rate
hypothesis (Robert Berner, Antonio Lasaga, Robert
Garrels, 1983)
sea floor spreading gtvolcanic activitygtCO2
input
17Age of sea floor
18CO2 Change in the last 100 myr Hypothesis 1
BLAG hypothesis sea floor spreading gtvolcanic
activitygtCO2 increase
100 ma
now
19Carbon cycle and stabilization of CO2
BLAG hypothesis sea floor spreading gtvolcanic
activitygtCO2 increase Further weathering
effect stabilizes CO2 and climate
20Atmospheric CO2 Evolution and Tectonic control
of CO2 hypothesis
21References for reading
Indonesian seaway, East Africa climate, and human
evolution Cane M. and P. Molnar, 2001 Closing
of Indonesian seaway as a precursor to east
African aridification around 3-4 million years
ago. Nature, 411, 157- 162
22Supercontinent Pangaea and Supermonsoon
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24End of Chapter 5
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28Experiments in South America More weathering on
the slopes of Andes