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Lecture 17

Lecture 17. Tectonic-scale Climate Change. Greenhouse / Icehouse Earth (Part II, p. 84-85; Ch. 4, p. 86-91). Geologic Time Scale. No ice sheets on land. Ice sheets on land. *. *. *. *. *. *. Ice House. Tectonic-scale Climate Change (Ch. 5, p. 103-112). Hundreds of millions of years.

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Lecture 17

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  1. Lecture 17 Tectonic-scale Climate Change

  2. Greenhouse/Icehouse Earth (Part II, p. 84-85; Ch. 4, p. 86-91) Geologic Time Scale No ice sheets on land Ice sheets on land * * * * * * Ice House

  3. Tectonic-scale Climate Change (Ch. 5, p. 103-112) Hundreds of millions of years Plate tectonics and drift concentrated continents at higher latitudes allowed for more ice cover, which reflected more sunlight and created a positive feedback to cause greater cooling.

  4. Tectonic-scale Carbon Dioxide Fluctuations (p. 91-99; p. 103-121) Seafloor spreading leads to increased periods of volcanic degassing of CO2, which causes warming. Higher temperatures leads to increased weathering, which will remove CO2 from the atmosphere and reverse warming in a negative feedback loop.

  5. Earth’s Climate History in the Last 550 Myr • Over the past 550 Myr, three Icehouse periods (430, 325-240, 35-0 Myr ago). 2. For most of the last 550 Myr or the earth’s entire history, the climate was much warmer than today. 3. Tectonic-scale climate change is caused by plate tectonics Land/ocean positions and sizes Ocean floor spreading/CO2 increase Mountain building (uplift) & weathering / CO2 decrease 4. Other causes. Part II p. 82-83; Ch. 4, 5, 6, 7

  6. Chemical weathering (chemical breakdown of minerals or rocks) Carbonic acid Examples: (Calcite) (calcium ions) Limestone + carbon dioxide + water  dissolved ions + bicarbonate CaCO3 + CO2 + H2O  Ca2+ + 2HCO3-

  7. The World 100 Myr Ago (p. 129-137) Flooding of The Continents

  8. Cretaceous  Greenhouse Earth Warm period of dinosaurs Evidence No record of glaciers or polar ice caps Faunal/floral zone latitudinal shift Isotopes  warmer oceans Environments shift with near tropics to the poles Oceans/Atmosphere/Land Features Sea level 100-200 m higher because of no polar ice caps Intense storms (hurricanes) because of warmer waters Stronger hydrologic cycle Less wind because lower T and P gradients globally More plants, more flowers; extent of dry land reduced by flooding Causes Sun-Earth relationship Land-sea configuration More oceans in low latitudeslower albedo More land in high latitudesmore plants More CO2 in atmosphere (4-8 x)

  9. 1. The last time atmospheric CO2 concentrations and temperatures were much higher than today was in the age of dinosaurs.2. Agriculture revolution began 10,000 years ago.3. Human population explosion in the past 100 years. Today: 6 billion 55 million years 6 5 million years 10million years 3.5 Million years 18,000 years 1 Million years 10,000 years 230,000 years 1,000 years PRESENT 100,000 years

  10. The only mammals living at this time were small rodents.

  11. Sea levels were much higher than today, and Texas was mostly under water What about Texas?

  12. Climate change was one important reason that the dinosaurs disappeared.

  13. Global Cooling Trend in the Last 55 Myr Ch. 7 Causes:decrease in ocean floor spreading rate; uplift weathering; ocean heat transport through gateways; ice-albedo feedbacks Cooling from leaf outline Cooling from ocean isotopes Decrease in spreading rate

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