1 / 28

Lecture 5: Plate Tectonics and Climate Last 550 Myr (chapter 4)

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.

jethro
Download Presentation

Lecture 5: Plate Tectonics and Climate Last 550 Myr (chapter 4)

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Lecture 5: Plate Tectonics and ClimateLast 550 Myr (chapter 4)

  2. Atmospheric CO2 Evolution

  3. Plate Tectonics Alfred Wegener (1914, German Meteorologist) proposed continental drift 3.2g/cm3 2.7g/cm3 >3.7g/cm3 1-10 cm/yr ==>5000km/100myr Soft acts as viscous fluid allows the tectonic plates above to move

  4. Formation of the continents Sea floor spreading • creation/destructoin of ocean crust since 175 myr Continental magnetic field • reconstruct continental positions (lat.) since 550 myr

  5. Paleomagnetic determination of past location of continentsthe position of basalt rocks on (older than 175 myr) Forming compass Molten lavas cools extruding onto the earth’s surface cools, the iron rich component aligns with the earth’s magnetic field at that time Fossil compass Further cooling forms basalts and fixes the magnetic field compasses, forming fossil compass Dating Potassium is also locked in basalts, its slow decaying rate (half time 1.3 Byr) allows us to identify the time compass pointing vertical compass pointing horizontal

  6. Paleomagnetic dating of ocean crust Magnetic reversal (over land) and magnetic lineations (in ocean)

  7. Moving Continents Gondwana and S. P. Glaciation 100 Myr ago Cretaceous Pangaea and Supermonsoon 200 Myr ago

  8. The Polar Position Hypothesis for alternative icehouse and greenhouse climate Glaciation occurs near polar position, But polar postion does NOT guarantee glaciation ? ? ? ? polar postion is NOT the only mechanism for glaciation What else?

  9. Atmospheric CO2 Evolution Why no ice sheet at S. Pole between 425-325Ma, 125-35 Ma? ? ? CO2?

  10. Tectonic Control of CO2 Removal: Uplift-Weathering Hypothesis Marueen Raymo et al., 1980s Uplifting ==> create fresh rock and mineral surfaces ==>stronger weathering ==> reduce CO2

  11. The magic of “breaking up”

  12. Quantifying 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

  13. Uplift and chemical weathering

  14. Atmospheric CO2 Evolution ? ?

  15. Tectonic control of CO2: BLAG spreading rate hypothesis (Robert Berner, Antonio Lasaga, Robert Garrels, 1983) sea floor spreading ==>volcanic activity==>CO2 input

  16. Age of sea floor

  17. CO2 Change in the last 100 myr: Hypothesis 1 BLAG hypothesis: sea floor spreading ==>volcanic activity==>CO2 increase 100 ma now

  18. Carbon cycle and stabilization of CO2 BLAG hypothesis: sea floor spreading ==>volcanic activity==>CO2 increase Further weathering effect stabilizes CO2 and climate

  19. Atmospheric CO2 Evolution and Tectonic control of CO2 hypothesis ? ?

  20. 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 References for reading

  21. Supercontinent Pangaea and Supermonsoon

  22. Extreme hotness may prevent glaciation Evidence of strong monsoon reversal: red beds Evidence of dry continents

  23. End of Chapter 5

  24. Experiments in South America: More weathering on the slopes of Andes

More Related