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Abstract:
Life has significantly altered the Earth’s atmosphere,
oceans and crust. To what extent has it also affected
interior geological processes? To address this question,
three models of geological processes are formulated:
mantle convection, continental crust uplift and erosion and
oceanic crust recycling. These processes are characterised
as non-equilibrium thermodynamic systems. Their states of
disequilibrium are maintained by the power generated from
the dissipation of energy from the interior of the Earth. Altering
the thickness of continental crust via weathering and
erosion affects the upper mantle temperature which leads to
changes in rates of oceanic crust recycling and consequently
rates of outgassing of carbon dioxide into the atmosphere.
Estimates for the power generated by various elements in the
Earth system are shown. This includes, inter alia, surface
life generation of 264TW of power, much greater than those
of geological processes such as mantle convection at 12TW.
This high power results from life’s ability to harvest energy
directly from the sun. Life need only utilise a small fraction
of the generated free chemical energy for geochemical transformations
at the surface, such as affecting rates of weathering
and erosion of continental rocks, in order to affect interior,
geological processes. Consequently when assessing the
effects of life on Earth, and potentially any planet with a significant
biosphere, dynamical models may be required that
better capture the coupled nature of biologically-mediated
surface and interior processes.
