Which geologic process is believed to have contributed to long-term climate stability enabling life to evolve?

• A. Volcanic eruptions
• B. Solar luminosity changes
• C. Plate tectonics
• D. Meteor impacts

Answer: (C)

Long-term climate stability enabling life comes from a self-regulating system built into plate tectonics. As continents move and are uplifted, silicate rocks on land react with atmospheric CO2 during weathering, removing CO2 from the air and storing it in carbonate minerals that are carried to the oceans. When these carbon-rich rocks are subducted and melt back into the mantle, CO2 is released again by volcanic activity. This ocean–continent–mantle carbon cycle links tectonics to atmospheric CO2 levels, creating a climate thermostat that keeps global temperatures within a range that allows oceans to remain liquid and life to persist and evolve over tens to hundreds of millions of years. Meteor impacts and changes in solar luminosity are external or episodic factors and don’t provide this long-term geologic regulation in the same integrated way.