Plate Tectonics and Climate GEOL 1130 The Chicken or the Egg Volcanic CO2 and chemical weathering function as Earths thermostat Is there one leading the change and the other reacting? Is there some other factor that governs the long-term swings in Earths climate? Lets look at last 550 million years of Earths history to test several hypotheses Effects of latitudinal position of continents? Polar Position Hypothesis Activity: Put Polar Position Hypothesis in words! Modeling Pangea: Boundary Conditions? Modeling Pangea: Output suggests interior aridity Modeling Pangea: Model results vs. geologic data Modeling Pangea: Output suggests extreme seasonality Modeling Pangea: Output suggests monsoons important Back to Chicken or Egg In thermostat, two possible factors that could be in drivers seat: Plate tectonics Weathering Two competing hypotheses BLAG (named after authors) or Spreading Rate Uplift-Weathering Activity: write out negative feedback loop that starts with spreading rate change and incorporates Earths thermostat as check Spreading Rate Hypothesis in words? Sources of CO 2 Does the last 550 million years of geologic history contain the record we need to test this hypothesis? Activity: Which time periods show the fastest and slowest rates of spreading, respectively? Uplift-Weathering Hypothesis Exposure of fresh rock due to uplift causes draw down of CO2 through chemical weathering Climate cools Fresh rock surfaces diminish if uplift diminishes and CO2 builds up Climate warms Uplifted areas have greater chemical (and physical) weathering Activity: Write out a negative feedback involving the uplift weathering hypothesis