“…Shear stresses on convergent plate boundaries provide resistance to plate motion and mantle convection, contribute to the support of topography above subduction zones, and influence processes such as metamorphism, dehydration, and melting that are important contributors to the global cycles of rocks and volatiles. It has been suggested that the strength of plate boundaries may control the magnitudes of earthquakes, with some authors attributing the largest earthquakes to plate boundaries with highest shear stresses (e.g., Hardebeck & Loveless, 2017;Scholz & Campos, 2012, while others contend that the reverse is the case (e.g., Gao & Wang, 2014;Wang & Bilek, 2011, 2014 or that the maximum magnitude is determined by variability, or lack thereof, in the magnitude of stress along subduction zones (e.g., Bletery et al, 2016Bletery et al, , 2017Schellart & Rawlinson, 2013;Wang & Bilek, 2011). The role of dissipative heating in metamorphism and melting at subduction zones is equally contentious; some authors regard dissipation as playing a negligible role (e.g., Abers et al, 2017;Syracuse et al, 2010), while others argue that shear stresses of order 10-100 MPa are required to explain the observations (e.g., England et al, 1992;Graham & England, 1975;Molnar & England, 1990;Peacock, 1992;Penniston-Dorland et al, 2015;Turcotte & Schubert, 1973).…”