Subduction network connectivity, a comparison between Earth and Venus

Earth’s size and composition make it comparable to Venus but these planets exhibit contrasting surface expressions due to their different tectonic regimes and surface recycling processes. Earth’s efficient recycling of its surface and the operation of plate tectonics are facilitated by the formation of extensive global subduction networks. During the Wilson Cycle, these networks drive periods of supercontinental breakup and active plate tectonics. We hypothesize that the formation of global subduction networks on Earth is promoted by the presence of water-rich continental sediments that reduce lithospheric friction at convergent margins. This is critical for inducing large-scale motion and reorganization of lithospheric plates, a key defining feature of modern plate tectonics. To explore this hypothesis, we developed a series of 3D global geodynamic models using the ASPECT code. These models reproduce 2 scenarios: (i) self-consistent plume-induced regional subduction and its reorganization into global subduction networks, (ii) prescribed inherited plate boundaries at 1Ga, demonstrating that sustained subduction activity is possible thanks to local frictional strength reduction. On Earth, such frictional reductions may fluctuate over time, driven by climatic events like Snowball Earth, which increase sediment flux and lubricate convergent plate boundaries. We compare these results with the results of models for Venus, where there is no liquid water at the surface, which implies higher frictional strength. We infer that without localized reduction of friction, regional subduction-like deformation on Venus’s dry surface is short-lived, failing to establish global subduction networks. However, in long-term, Venus can still experience episodic resurfacing as its lithosphere becomes unstable and collapses into the asthenosphere. Comparison of Earth’s and Venus’s tectonic styles highlights the role of surface water and water-rich sediments in sustaining large-scale and long-term subduction and in the development of a global network of subduction zones and plate boundaries, which is a characteristic of modern plate tectonics.