lecture 5: plate tectonics and climate last 550 myr (chapter 4)
DESCRIPTION
Lecture 5: Plate Tectonics and Climate Last 550 Myr (chapter 4). Atmospheric CO 2 Evolution. Plate Tectonics Alfred Wegener (1914, German Meteorologist ) proposed continental drift. 3.2g/cm 3. 2.7g/cm 3. >3.7g/cm 3. 1-10 cm/yr ==>5000km/100myr. - PowerPoint PPT PresentationTRANSCRIPT
![Page 1: Lecture 5: Plate Tectonics and Climate Last 550 Myr (chapter 4)](https://reader035.vdocuments.us/reader035/viewer/2022062217/56813e1d550346895da7fcd2/html5/thumbnails/1.jpg)
Lecture 5:
Plate Tectonics and Climate
Last 550 Myr
(chapter 4)
![Page 2: Lecture 5: Plate Tectonics and Climate Last 550 Myr (chapter 4)](https://reader035.vdocuments.us/reader035/viewer/2022062217/56813e1d550346895da7fcd2/html5/thumbnails/2.jpg)
Atmospheric CO2 Evolution
![Page 3: Lecture 5: Plate Tectonics and Climate Last 550 Myr (chapter 4)](https://reader035.vdocuments.us/reader035/viewer/2022062217/56813e1d550346895da7fcd2/html5/thumbnails/3.jpg)
Plate TectonicsAlfred Wegener (1914, German Meteorologist) proposed continental drift
1-10 cm/yr ==>5000km/100myr
2.7g/cm3
3.2g/cm3
>3.7g/cm3
Soft acts as viscous fluid allows the tectonic plates above to move
![Page 4: Lecture 5: Plate Tectonics and Climate Last 550 Myr (chapter 4)](https://reader035.vdocuments.us/reader035/viewer/2022062217/56813e1d550346895da7fcd2/html5/thumbnails/4.jpg)
Sea floor spreading
creation/destructoin of ocean crust
since 175 myr
Continental magnetic field
reconstruct continental positions (lat.)
since 550 myr
Formation of the continents
![Page 5: Lecture 5: Plate Tectonics and Climate Last 550 Myr (chapter 4)](https://reader035.vdocuments.us/reader035/viewer/2022062217/56813e1d550346895da7fcd2/html5/thumbnails/5.jpg)
![Page 6: Lecture 5: Plate Tectonics and Climate Last 550 Myr (chapter 4)](https://reader035.vdocuments.us/reader035/viewer/2022062217/56813e1d550346895da7fcd2/html5/thumbnails/6.jpg)
Paleomagnetic determination of past location of continents the position of basalt rocks on (older than 175 myr)
compass pointing horizontal
compass pointing vertical
Forming compassMolten lavas cools extruding onto the earth’s surface cools, the iron rich component aligns with the earth’s magnetic field at that time
Fossil compassFurther cooling forms basalts and fixes the magnetic field compasses, forming fossil compass
DatingPotassium is also locked in basalts, its slow decaying rate (half time 1.3 Byr) allows us to identify the time
![Page 7: Lecture 5: Plate Tectonics and Climate Last 550 Myr (chapter 4)](https://reader035.vdocuments.us/reader035/viewer/2022062217/56813e1d550346895da7fcd2/html5/thumbnails/7.jpg)
Magnetic reversal (over land) and magnetic lineations (in ocean)
Paleomagnetic dating of ocean crust
![Page 8: Lecture 5: Plate Tectonics and Climate Last 550 Myr (chapter 4)](https://reader035.vdocuments.us/reader035/viewer/2022062217/56813e1d550346895da7fcd2/html5/thumbnails/8.jpg)
Moving Continents
200 Myr ago
100 Myr ago
Cretaceous
Pangaea and Supermonsoon
Gondwana and S. P. Glaciation
![Page 9: Lecture 5: Plate Tectonics and Climate Last 550 Myr (chapter 4)](https://reader035.vdocuments.us/reader035/viewer/2022062217/56813e1d550346895da7fcd2/html5/thumbnails/9.jpg)
The Polar Position Hypothesis
for alternative icehouse and greenhouse climate
Glaciation occurs near polar position,
But
polar postion does NOT guarantee glaciation
What else?
![Page 10: Lecture 5: Plate Tectonics and Climate Last 550 Myr (chapter 4)](https://reader035.vdocuments.us/reader035/viewer/2022062217/56813e1d550346895da7fcd2/html5/thumbnails/10.jpg)
Atmospheric CO2 Evolution
? ?CO2?
Why no ice sheet at S. Pole between 425-325Ma, 125-35 Ma?
![Page 11: Lecture 5: Plate Tectonics and Climate Last 550 Myr (chapter 4)](https://reader035.vdocuments.us/reader035/viewer/2022062217/56813e1d550346895da7fcd2/html5/thumbnails/11.jpg)
Tectonic Control of CO2 Removal:
Uplift-Weathering HypothesisMarueen Raymo et al., 1980s
Uplifting ==> create fresh rock and mineral surfaces
==>stronger weathering ==> reduce CO2
![Page 12: Lecture 5: Plate Tectonics and Climate Last 550 Myr (chapter 4)](https://reader035.vdocuments.us/reader035/viewer/2022062217/56813e1d550346895da7fcd2/html5/thumbnails/12.jpg)
The magic of “breaking up”
![Page 13: Lecture 5: Plate Tectonics and Climate Last 550 Myr (chapter 4)](https://reader035.vdocuments.us/reader035/viewer/2022062217/56813e1d550346895da7fcd2/html5/thumbnails/13.jpg)
Quantifying weathering rate with time
Why fresh rocks has a much higher weathering rate (over 100 times…)
1)Fresh rocks has more weathering materials – fresh, unweathered silicates2)Fragmentation increases surface area
1
100
![Page 14: Lecture 5: Plate Tectonics and Climate Last 550 Myr (chapter 4)](https://reader035.vdocuments.us/reader035/viewer/2022062217/56813e1d550346895da7fcd2/html5/thumbnails/14.jpg)
Uplift and chemical weathering
![Page 15: Lecture 5: Plate Tectonics and Climate Last 550 Myr (chapter 4)](https://reader035.vdocuments.us/reader035/viewer/2022062217/56813e1d550346895da7fcd2/html5/thumbnails/15.jpg)
Atmospheric CO2 Evolution
? ?
![Page 16: Lecture 5: Plate Tectonics and Climate Last 550 Myr (chapter 4)](https://reader035.vdocuments.us/reader035/viewer/2022062217/56813e1d550346895da7fcd2/html5/thumbnails/16.jpg)
Tectonic control of CO2:
BLAG spreading rate hypothesis
(Robert Berner, Antonio Lasaga, Robert Garrels, 1983)
sea floor spreading ==>volcanic activity==>CO2 input
![Page 17: Lecture 5: Plate Tectonics and Climate Last 550 Myr (chapter 4)](https://reader035.vdocuments.us/reader035/viewer/2022062217/56813e1d550346895da7fcd2/html5/thumbnails/17.jpg)
Age of sea floor
![Page 18: Lecture 5: Plate Tectonics and Climate Last 550 Myr (chapter 4)](https://reader035.vdocuments.us/reader035/viewer/2022062217/56813e1d550346895da7fcd2/html5/thumbnails/18.jpg)
100 ma
now
BLAG hypothesis:
sea floor spreading ==>volcanic activity==>CO2 increase
CO2 Change in the last 100 myr: Hypothesis 1
![Page 19: Lecture 5: Plate Tectonics and Climate Last 550 Myr (chapter 4)](https://reader035.vdocuments.us/reader035/viewer/2022062217/56813e1d550346895da7fcd2/html5/thumbnails/19.jpg)
BLAG hypothesis:
sea floor spreading ==>volcanic activity==>CO2 increase
Further weathering effect stabilizes CO2 and climate
Carbon cycle and stabilization of CO2
![Page 20: Lecture 5: Plate Tectonics and Climate Last 550 Myr (chapter 4)](https://reader035.vdocuments.us/reader035/viewer/2022062217/56813e1d550346895da7fcd2/html5/thumbnails/20.jpg)
? ?
Atmospheric CO2 Evolution
and Tectonic control of CO2 hypothesis
![Page 21: Lecture 5: Plate Tectonics and Climate Last 550 Myr (chapter 4)](https://reader035.vdocuments.us/reader035/viewer/2022062217/56813e1d550346895da7fcd2/html5/thumbnails/21.jpg)
References 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
![Page 22: Lecture 5: Plate Tectonics and Climate Last 550 Myr (chapter 4)](https://reader035.vdocuments.us/reader035/viewer/2022062217/56813e1d550346895da7fcd2/html5/thumbnails/22.jpg)
Supercontinent Pangaea and Supermonsoon
![Page 23: Lecture 5: Plate Tectonics and Climate Last 550 Myr (chapter 4)](https://reader035.vdocuments.us/reader035/viewer/2022062217/56813e1d550346895da7fcd2/html5/thumbnails/23.jpg)
Evidence of strong monsoon reversal:
red beds
Extreme hotness may prevent glaciation
Evidence of dry continents
![Page 24: Lecture 5: Plate Tectonics and Climate Last 550 Myr (chapter 4)](https://reader035.vdocuments.us/reader035/viewer/2022062217/56813e1d550346895da7fcd2/html5/thumbnails/24.jpg)
End of Chapter 5
![Page 25: Lecture 5: Plate Tectonics and Climate Last 550 Myr (chapter 4)](https://reader035.vdocuments.us/reader035/viewer/2022062217/56813e1d550346895da7fcd2/html5/thumbnails/25.jpg)
![Page 26: Lecture 5: Plate Tectonics and Climate Last 550 Myr (chapter 4)](https://reader035.vdocuments.us/reader035/viewer/2022062217/56813e1d550346895da7fcd2/html5/thumbnails/26.jpg)
![Page 27: Lecture 5: Plate Tectonics and Climate Last 550 Myr (chapter 4)](https://reader035.vdocuments.us/reader035/viewer/2022062217/56813e1d550346895da7fcd2/html5/thumbnails/27.jpg)
![Page 28: Lecture 5: Plate Tectonics and Climate Last 550 Myr (chapter 4)](https://reader035.vdocuments.us/reader035/viewer/2022062217/56813e1d550346895da7fcd2/html5/thumbnails/28.jpg)
Experiments in South America:
More weathering on the slopes of Andes