Researchers have captured a subduction zone off Vancouver Island in the act of breaking apart, according to a study in Science Advances. The Cascadia subduction zone, where the Juan de Fuca and Explorer plates slide beneath North America, shows large faults and fractures cutting through the sinking plate. Lead author Brandon Shuck of Louisiana State University said it is the first clear picture of a subduction zone caught in the process of dying.
The team combined earthquake records with seismic reflection data from the 2021 CASIE21 experiment, towing a 15-kilometer streamer behind a ship to image structures beneath the seafloor. They found an enormous offset where part of the slab has dropped by roughly five kilometers, and a tear stretching about 75 kilometers. Along that tear, some sections still produce earthquakes while others are quiet, suggesting those pieces have already separated.
Rather than shutting down all at once, the subduction zone appears to be dismantling piece by piece. Transform faults act like scissors, isolating fragments that become microplates. Each breakup may take millions of years, but together they can end an entire subduction zone. The researchers say this piecewise process could help explain ancient plate fragments and volcanic activity, and hidden breaks beneath Cascadia may influence future earthquakes.