Submarine canyons are massive underwater valleys that funnel sediment, nutrients, and carbon from coastal areas into the deep ocean. This natural transport system plays a vital role in Earth’s climate by helping bury carbon on the seafloor, keeping it out of the atmosphere.

For years, scientists have debated how these canyons form—whether they’re carved by sediment from rivers or shaped by deep-sea processes. To investigate canyon forming processes, we analyzed data from over 2,000 submarine canyons around the world using advanced spatial modeling. We found that canyon formation is driven mainly by tectonic forces—like seafloor uplift and deformation—not by sediment input from rivers or nearby mountains. Steeper continental slopes, shaped by tectonics, are much more likely to host canyons. In contrast, land-based factors had far less influence than previously thought.

This matters because canyons significantly boost the burial of organic carbon in the deep sea. In some regions, they raise carbon burial efficiency from typical values of 10–30% to as high as ~80%. Our findings offer new insights into how the seafloor evolves and how the deep ocean helps regulate Earth’s climate over long timescales—crucial for understanding both past and future climate change.