Formation of global subduction networks and large-scale convection facilitated by climate-induced weakening of convergent plate boundaries.

On Earth, the long-term development of plate tectonics is often explained by the Wilson cycle, which spans hundreds of millions of years and involves the repeated opening and closing of ocean basins through lithosphere recycling and continental movement. These cycles feature alternating phases of supercontinent assembly and breakup. Their dynamics are fundamentally connected to mantle convection and to subduction. Subduction networks are essential for both supercontinent breakup and rapid plate movements. We suggest that the development and longevity of Earth's global subduction networks are affected by water-rich sediments resulting from continental erosion. These sediments can accumulate at convergent margins and reduce their frictional strength, promoting long-lasting subduction and sustained slab rollback. As individual subduction systems expand and link together, they can create a global subduction network that increases plate mobility and promotes large-scale plate reorganizations, ultimately supporting a return to continental assembly. To test this hypothesis, we use the ASPECT numerical code, combined with the Geodynamic World Builder to run a suite of three-dimensional global geodynamic models by prescribing an initial plate configuration using GPlately. We examine two end-member Earth-like scenarios: (i) models without initial prescribed subduction zones and ridges, where plume-driven regional subduction evolves into a global subduction network, and (ii) a setup with pre-defined plate boundaries and subduction zones corresponding to the GPlates-derived configuration at 1 Ga, demonstrating that sustained subduction can be maintained when friction is locally reduced. On Earth, such frictional weakening may vary over time in response to climatic conditions, such as Snowball Earth episodes, which enhance erosion, sediment flux at plate boundaries. Our results highlight the fundamental role of surface water and sediment supply in regulating the longevity of subduction systems and, ultimately, the emergence and maintenance of large-scale plate tectonics.