A Thermal Evolution Model of the Earth Including the Biosphere, Continental Growth and Mantle Hydration

Abstract:

By harvesting solar energy and converting it to chemical energy, photosynthetic life plays an important role in the energy budget of Earth [2]. This leads to alterations of chemical reservoirs eventually affecting the Earth’s interior [4]. It further has been speculated [3] that the formation of continents may be a consequence of the evolution life. A steady state model [1] suggests that the Earth without its biosphere would evolve to a steady state with a smaller continent coverage and a dryer mantle than is observed today.

We present a model including (i) parameterized thermal evolution, (ii) continental growth and destruction, and (iii) mantle water regassing and outgassing. The biosphere enhances the production rate of sediments which eventually are subducted. These sediments are assumed to (i) carry water to depth bound in stable mineral phases and (ii) have the potential to suppress shallow dewatering of the underlying sediments and crust due to their low permeability. We run a Monte Carlo simulation for various initial conditions and treat all those parameter combinations as success which result in the fraction of continental crust coverage observed for present day Earth. Finally, we simulate the evolution of an abiotic Earth using the same set of parameters but a reduced rate of continental weathering and erosion.

Our results suggest that the origin and evolution of life could have stabilized the large continental surface area of the Earth and its wet mantle, leading to the relatively low mantle viscosity we observe at present. Without photosynthetic life on our planet, the Earth would be geodynamical less active due to a dryer mantle, and would have a smaller fraction of continental coverage than observed today.

References

[1] Höning, D., Hansen-Goos, H., Airo, A., Spohn, T., 2014. Biotic vs. abiotic Earth: A model for mantle hydration and continental coverage. Planetary and Space Science 98, 5-13.
[2] Kleidon, A., 2010. Life, hierarchy, and the thermodynamic machinery of planet Earth. Phys. Life Rev. 7, 428–460.
[3] Rosing, M .T., et al., 2006. The rise of continents – an essay on the geologic consequences of photosynthesis. Paleogeogr., Paleoclimatol., Paleoecol. 232, 99–113.
[4] Sleep, N.H., Bird, D.K., Pope, E., 2012. Paleontology of Earth's mantle. Annu. Rev. Earth Planet. Sci. 40, 277–300.