Tectonic motion reshapes Earth’s long-term carbon balance, study argues

Researchers used plate-motion reconstructions combined with carbon-transport models to reassess how carbon moves between the ocean, crust and atmosphere over the last half-billion years. The analysis attributes greater long-term control of atmospheric CO2 to spreading centers and rift systems because they govern how carbon-rich sediments are produced and later returned to the mantle at subduction zones. In warm intervals the balance favored net carbon release, while cold intervals were marked by stronger sequestration into marine sediments — a switching mechanism tied to plate-driven sediment pathways rather than volcanic arcs alone. The team demonstrates that the proliferation of calcifying plankton altered where much carbon was locked into seafloor deposits, amplifying the role of arc volcanism only after those organisms spread widely. Before that biological shift, mid-ocean ridges and rifts were comparatively more important sources of CO2 at geological timescales. By explicitly tracing sediment production, transport and subduction through plate reconstructions, the work produces a mechanistic link between tectonics and long-term greenhouse–icehouse cycles. This approach narrows a key uncertainty in paleoclimate drivers by shifting emphasis from surface volcanism as a lone culprit to the conveyor-belt behavior of ocean basins. For climate-modelers, the finding means that realistic boundary conditions over millions of years require accounting for sediment routing and changes in seafloor carbon burial rates tied to plate geometry. The conclusions do not undermine anthropogenic warming today but provide context: natural tectonic processes operate on far longer timescales and have modulated background CO2 over epochs. Incorporating these tectono-sedimentary controls can improve simulations of ancient climates and strengthen confidence in projections of Earth system sensitivity. The study therefore offers a recalibrated narrative of how solid-Earth processes and marine biology combined to set atmospheric carbon on geological timescales, and it supplies concrete inputs that can be tested in coupled geochemical–tectonic models.