Researchers from Section 4.5 find evidence that a critical crustal thickness of about 42 km corresponds to a stable thermodynamic equilibrium between the internal energy of the plate and tectonic forces. This critical crustal thickness corresponds approximately to the global average of today's continental crust and is also typical for stable old cratons that usually lie far from the tectonic plate boundaries. Using data-driven thermomechanical modelling of the Alpine-Himalayan collision zone, we show why deviations from this equilibrium lead to continental deformation. The decisive factor here is the radiogenic heat produced (i.e., internal heating sources) by the crust. If the crust is thicker than the critical value, because of the work done by the plate-boundary forces increasing the gravitational potential energy, the additional radiogenic heat causes the internal energy to increase and help dissipate the acquired potential energy in the form of diffuse deformation. This explains the widely distributed occurrence of seismicity in the area of the collision zone in contrast to localized deformation at plate boundaries. A dissipative thermodynamic feedback between thermal and mechanical relaxation of the increased internal energy eventually leads to equilibrium. Our results also suggest a genetic link between the thermochemical state of the crust and the tectonic evolution of silicate Earth-like planets.
Original publication: Kumar, A., Cacace, M. & Scheck-Wenderoth, M. – Thermodynamics of continental deformation. Sci Rep 13, 19920 (2023).
doi.org/10.1038/s41598-023-47054-3