Trench dynamics: Effects of dynamically migrating trench on subducting slab morphology and characteristics of subduction zones systems

Modeling the Inception of Supercontinent Breakup: Stress State and the Importance of Orogens

“…To define the position of a trench, we firstly recompute the position of the weak zone based on a given rate of subduction retreat, and then reassign a new viscosity here at every time step. In this work, the viscosity of the weak zone is either 1/30 or 1/100 of that of the oceanic lithosphere, consistent with the range of 0.01–0.1 used by previous studies (e.g., Holt et al, ; Yoshida, ; Zhong et al, ). For supercontinent with orogens, the weak zone is segmented where orogens meet the edge of the supercontinent (Figure ).…”

“…Besides the dispersal of continental blocks, the normal stress σ θθ for the above two models after a persistent 50 Myr subduction retreat are also examined (Figures 10c and 10f). Both the homogeneous and orogenembedded supercontinent models show an extensional state (~20 MPa for the former, and 5-50 MPa for the latter) at the continental margin near the subduction zone, which is consistent with the extensional continental margin observed in the present-day circum-Pacific subduction zones (except for the Andes) and predicted by previous models of subduction retreat (e.g., Dal Zillo et al, 2018;Yoshida, 2017). We also observe a significant decrease in the magnitude of σ θθ in the interiors of supercontinent approximately 50 Myr after the supercontinent breakup time (t1) and with subduction retreat: 20-50 MPa in model with homogeneous supercontinent (comparing Figures 5a and 10c) and 40-100 MPa in model with orogens (comparing Figure 10f's top and bottom panels).…”

“…These studies commonly emphasized the importance of plume‐push force during the breakup of the supercontinent. Works focusing on the stress produced by subduction retreat (Bercovici & Long, ; Dal Zilio et al, ; Holt et al, ; Lowman & Jarvis, ; Lu et al, ; Yoshida, ), on the other hand, either omitted the plume‐push force and the interaction between plumes and subduction retreat (e.g., Dal Zilio et al, ), or inserted ad‐hoc plumes beneath the continent (e.g., Lu et al, ). The capacities of these latter studies in exploring the full force of supercontinent breakup are therefore restricted by their inability of generating dynamically self‐consistent plumes (or plume cluster) beneath the supercontinent.…”

“…Understanding what drives the breakup of supercontinents is crucial for understanding the dynamic driving force of plate tectonics. Major forces being considered include the push force from uprising subcontinental mantle plumes (Buiter & Torsvik, 2014;Cande & Stegman, 2011;Gurnis, 1988;Koptev et al, 2015;Li et al, 1999Li et al, , 2008Zhang et al, 2018), the traction force of mantle convection (Morgan, 1972;Wilson, 1973), and the drag force from retreating subduction at the margin of the supercontinent (e.g., Bercovici & Long, 2014;Dal Zilio et al, 2018;Lowman & Jarvis, 1995;Yoshida, 2017). Among the three mechanisms, it has been argued that the extensional force caused by plume push is more important than that from subduction retreat at least during the early stage of the breakup (Zhang et al, 2018).…”

On mantle drag force for the formation of a next supercontinent as estimated from a numerical simulation model of global mantle convection

“…It is still a controversial issue in mantle dynamics as to whether the suction force induced by the subduction retreat and the resulting extensional stress in the continental plates exert an effective force on the supercontinental breakup (e.g. Yoshida, ). Zhang et al.…”