A gaping hole in a dying tectonic plate beneath the ocean along the West Coast of the United States may be wreaking havoc at Earth’s surface, but not in a way most people might expect.

This gash is so big it may trigger earthquakes off the coast of Northern California and could explain why central Oregon has volcanoes, a new study found.

The researchers in the new study aren’t the first to suggest that the Michigan-size Juan de Fuca (pronounced “wahn de fyoo-kuh”) plate has a tear. But thanks to a new, detailed dataset, they’re the first to say so with certainty.

“Where other people had debated whether or not it [the tear] was there, we can pretty confidently say that it’s real,” study lead researcher William Hawley, a doctoral student in the Earth and Planetary Science Department at the University of California, Berkeley, told Live Science.

Read more: live science