Plate Tectonics and Climate GEOL 1130
Jan 22, 2016
Plate Tectonics and Climate
GEOL 1130
The Chicken or the Egg
• Volcanic CO2 and chemical weathering function as Earth’s thermostat– Is there one leading the change and the other
reacting?– Is there some other factor that governs the
long-term swings in Earth’s climate?
• Let’s look at last 550 million years of Earth’s 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 Earth’s thermostat as check
Spreading Rate Hypothesis in words?
Sources of CO2
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 ofspreading, 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