For the first time, scientists have observed a tectonic plate actively breaking apart in the Pacific Ocean. This rare event reveals how massive slabs of Earth's crust fragment into smaller plates.
Researchers from Louisiana State University and Columbia University's Lamont-Doherty Earth Observatory detected the initial stages of fragmentation in the Juan de Fuca and Explorer plates off the coast of Vancouver Island. These plates are subducting beneath the North American plate.
Using seismic reflection tomography, the team created detailed images of faults developing within the plates. One major fault shows a vertical slip of nearly 5 kilometers (3 miles).
Lead author Brandon Shuck compared the process to starting a heavy train rolling uphill. "It takes immense force to initiate subduction, but once it starts, it accelerates. To stop it, you need a train wreck," he explained.
The study also identified a 75-kilometer (47-mile) fault zone where seismic activity has shifted. Some areas remain prone to earthquakes, while others have gone silent—a sign that plate fragments have completely detached from the main body.
This discovery explains the origin of mysterious "relic" microplates found off California's coast. The new data will be incorporated into models predicting seismic risks.
Learn more: tectonic plates, subduction zone, earthquake.
