Earth's Crust is Tearing Apart Off the Pacific Northwest—and That's Not Necessarily Bad News

janrinok writes:

https://phys.org/news/2025-10-earth-crust-pacific-northwest-necessarily.html

With unprecedented clarity, scientists have directly observed a subduction zone-the collision point where one tectonic plate dives beneath another-actively breaking apart. The discovery, reported in Science Advances, sheds new light on how Earth's surface evolves and raises fresh questions about future earthquake risks in the Pacific Northwest.

Subduction zones are the sites of Earth's most powerful tectonic events. They drive continents across the globe, unleash devastating earthquakes and volcanic eruptions, and recycle the planet's crust deep into the mantle.

But they don't last forever. If they did, continents would endlessly collide and stack up, erasing oceans and wiping out the record of Earth's past. The big question geologists have wrestled with is: how exactly do these mighty systems finally shut down?

"Getting a subduction zone started is like trying to push a train uphill-it takes a huge effort," said Brandon Shuck, an assistant professor at Louisiana State University and lead author of the study. "But once it's moving, it's like the train is racing downhill, impossible to stop. Ending it requires something dramatic-basically, a train wreck."

[...] Off the coast of Vancouver Island, in a region of Cascadia where the Juan de Fuca and Explorer plates slowly move beneath the North American plate, scientists have found the answer. Using a combination of seismic reflection imaging-essentially an ultrasound of Earth's subsurface-and detailed earthquake records, the team has captured a subduction zone in the process of tearing itself apart.

[...] The researchers sent sound waves from the ship into the seafloor and recorded the echoes using a 15-kilometer-long streamer of underwater listening devices. This produced high-resolution images of faults and fractures deep beneath the ocean floor, revealing places where the plate is snapping.

"This is the first time we have a clear picture of a subduction zone caught in the act of dying," said Shuck. "Rather than shutting down all at once, the plate is ripping apart piece by piece, creating smaller microplates and new boundaries. So instead of a big train wreck, it's like watching a train slowly derail, one car at a time."

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