Faraway tectonic forces may have accelerated the Gulf of California rifting

Faraway tectonic forces may have accelerated the Gulf of California rifting Robert Egan Senior Editor When the Baja California peninsula broke from mainland Mexico nearly 12 million years ago, it gave rise to the Gulf of California. New research suggests that this process of continental rifting was greatly accelerated due to tectonic forces on the opposite side of the Pacific Ocean. The finding comes from a study published in Science, led by researchers at The University of Texas at Austin, Czech Academy of Sciences, Helmholtz Centre for Geosciences and Roma Tre University. Two subduction zones, distant effects "What we think happened in the western Pacific is that there was once a single subduction zone, but then a second one formed," said Xiang He, a study co-author and graduate research assistant at the Jackson School of Geosciences' Department of Earth and Planetary Sciences and University of Texas Institute for Geophysics (UTIG). A subduction zone is a region where two tectonic plates collide, and one slides under the other. When two separate subduction processes happen simultaneously and interact, that's called a double subduction zone. Most of the impact happened around Japan, which is where the slabs were moving due to the double subduction. But the team's computer simulations showed that in plates near Baja California, the double subduction generated extra extensional stress, which can lead to thinning and cause fault lines. "What surprised us was how clearly the stress increase appeared near Baja California, so far from the subduction zones in the western Pacific. Other places do not have obvious stress changes—only Baja did," said He, who led the study's numerical modeling. Modeling the extra tectonic pull The researchers compared single versus double subduction zones by building a 3D physics-based model using ASPECT, open-source community software. By integrating data on current slab geometries, mantle anomalies and lithospheric structures, they calculated mantle flow, plate velocities and lithospheric stresses. They then analyzed the differences between the modeled configurations. While the Gulf of California was already opening due to regional lithosphere weaknesses, the researchers believe the double subduction near Japan may have sped up the process by approximately 30–80 million years. "It turns out that if you have two subducting slabs pulling, the trailing plate doesn't move twice as fast, but sort of 1.7 times that," said Thorsten Becker, a co-author of the study and a professor at the Department of Earth and Planetary Sciences and a senior research scientist at UTIG. Global forces and regional hazards The researchers hope their model could be used as a reference for how plates are pushed together in places that have complex geometries and are prone to earthquakes. One well-known current analog is in East Africa, which experiences earthquakes and volcanic eruptions during rifting, signs that the continent is slowly breaking apart. "What's new is that we can better model such global plate interactions, which links to the evolution of subduction," said Becker. "We have to worry about these other drivers. If Africa now were to experience additional pulls, the added oomph could reorganize this rift." Becker says the team is excited to use supercomputers and advanced modeling to capture complex global effects and then zoom in to understand regional impacts. "We're trying to do better in providing this information about global tectonic forcing, which might actually change on timescales that are relevant even for understanding plate margin evolution from a hazard's perspective," he said. Publication details Guido M. Gianni et al., Western Pacific double subduction drives Gulf of California rifting, Science (2026). DOI: 10.1126/science.aef5187 Journal information: Science Provided by University of Texas at Austin