A Leak at the Bottom of the Sea May Be a Harbinger of Doom

University of Washington
University of Washington

The Cascadia Subduction Zone (CSZ) is a massive fault line stretching from Vancouver Island to Northern California—and it’s the source of the vast majority of earthquakes and tsunamis in the region. In fact, scientists believe that the fault line will likely be the source of the next Big One, an anticipated megathrust earthquake so powerful it’ll wreak death and destruction the likes of which we’ve never seen before from a geological event.

So, it goes without saying that researchers have a special interest in studying the CSZ—and they may have uncovered something that could clue us in on what’s going on with the incredibly powerful ticking time bomb.

Researchers at the University of Washington found a warm liquid seeping out of the ocean floor near the zone roughly 50 miles off the coast of Newport, Oregon. The team suspects that the underwater spring, called Pythia’s Oasis, might be connected to the CSZ—and causing the fault line to take on more stress as it leaks. They published their findings on Jan. 25 in the journal Science Advances.

“Pythias Oasis provides a rare window into processes acting deep in the seafloor, and its chemistry suggests this fluid comes from near the plate boundary,” Deborah Kelley, a professor of oceanography at UW and a co-author of the new paper, said in a statement. “This suggests that the nearby faults regulate fluid pressure and megathrust slip behavior along the central Cascadia Subduction Zone.”

The team discovered the leak after spotting plumes of methane bubbles nearly a mile below the surface of the ocean. After sending an underwater drone to investigate, they discovered that water with a different chemical composition from the surrounding seawater was seeping into the ocean from a hole in the ground “like a firehose,” Evan Soloman, a fellow UW oceanographer and a co-author of the paper, said in a statement. “That’s something that I’ve never seen and to my knowledge has not been observed before.”

Further analysis found that the water was 16 degrees Fahrenheit warmer than the seawater around it. The authors suspect that the fluid’s source is roughly 2 miles below the ocean floor at the CSZ fault line where temperatures sit around 300 to 500 degrees Fahrenheit.

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Why is that a big deal? The researchers say that the fluid might be acting as a kind of pressure regulator between the continental plate and the ocean plate. The more fluid that is in the cracks of the faults, the less pressure there is between the two plates as they smash into each other.

So less fluid means there’s more pressure building between the two plates. This can create a lot of stress on the region and a whole lot more potential energy that could unleash itself as a devastating earthquake.

“The megathrust fault zone is like an air hockey table,” Solomon explained. “If the fluid pressure is high, it’s like the air is turned on, meaning there’s less friction and the two plates can slip. If the fluid pressure is lower, the two plates will lock. That’s when stress can build up.”

The authors wrote that they don’t know whether or not Pythia’s Oasis is the “only seep of its kind,” and suggest that there could be similar seeps in that region of the CSZ. As such, seismologists should consider these seeps in future models of the CSZ.

So while there’s no telling when the next Big One is going to happen, it’s at least somewhat comforting to know that we’re still learning all we can about the CSZ to make sure we’re prepared for it when it does come.

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