Life with and Life without Plate Tectonics
Friday, 19 December 2014: 1:55 PM
The long standing notion that plate tectonics is key to planetary habitability is critically evaluated. The purported necessity of plate tectonics for planetary habitability is tied to volatile cycling, atmosphere retention, and carbon burial. Plate tectonics is not unique in allowing for cycling of volatiles between the interior of a planet and its atmosphere. Volcanism can be maintained on a single plate planet over geologic time scales and several non-plate tectonic recycling mechanisms are viable on such a planet. The frequency and efficiency of these modes of volatile recycling and volcanism are critical to evaluating whether they are sufficient to stabilize climate. An episodic mode of a volcanism and subduction also has the potential to provide the level of volatile cycling needed to maintain habitability. We combine solid planet models of degassing and regassing with climate, surface processes, and carbon sequestration models to determine the level to which habitable conditions can be maintained in the absence of plate tectonics. We also review arguments that the Earth operated in a different tectonic mode over its initial 2-3 billion years of geologic evolution, a time period over which the planet was habitable. Collectively our results suggests that habitable conditions can exist independent of the tectonic mode of a planet. However, O-rich atmospheres and complex life might require continuous recycling processes and ocean floor uplift to bury carbon onto stable platforms as provided by plate tectonics.