Mysterious leak found on ocean floor in high seismic risk area
The earthquakes cannot yet be predicted, but scientists have on their radar the subduction zone of Cascadiaa submarine fault of more than 1,100 kilometers that stretches from the Canadian province of British Columbia to northern California on the west coast of the United States, as a high-risk seismic zone capable of causing earthquakes of magnitude 8 or greater followed by tsunamis. A study conducted by the University of Washington (UW) has discovered what scientists have named ‘Pythias Oasis’, a warm, chemically distinct liquid seepage. to the water emerging from the seafloor about 50 miles off Newport, Oregon (USA).
According to a recent UW press release, the results of the research, published in the journal at. Science Advances last January, suggest that this “unique underwater spring” comes directly from the Cascadia subduction zone, specifically from a point about four kilometers below the seafloor at the plate boundary, which “regulates tectonic stresses on the offshore fault.” This fluid emanating from the seafloor in this seismic hazard zone is “like a lubricant leak,” described Evan Solomon, UW associate professor of oceanography and co-author of the paper.
As the researchers explain, the finding came in 2015 following the weather-delayed delay of the Regional Cabled Array expedition cruise ship, whose sonar picked up some unexpected columns of bubbles about three-quarters of a mile below the ocean surface.
Further exploration with a underwater robot revealed that the bubbles were “a minor component of the warm, chemically distinct fluid that bubbles up from the seafloor sediment.”
As Evan Solomon explains, “they explored in that direction and what they saw was not just methane bubbles, but water coming out of the seafloor like a fire hose. That’s something I’ve never seen before and, to my knowledge, had never been observed before.”.
Later observations showed that the fluid leaving the seabed is. nine degrees Celsius warmer than the surrounding seawater.. Calculations suggest that the fluid comes directly from the Cascadia ‘megathrust’, where temperatures are estimated to be between 150 and 250 degrees Celsius.
As the researchers explain, fluid loss is the Cascadia fault is important because it reduces fluid pressure between sediment particles and thus increases friction between the oceanic and continental plates. In Solomon’s words, “the ‘megathrust’ zone is. like an air field hockey table“.
“If the fluid pressure is highit is as if the air is on, which means that there are less friction and the two plates can slide. Conversely, if the fluid pressure is lower, the two plates will lock; that’s when stress can build up,” he has warned. In other words, less lubricant means that stress can generate a damaging earthquake.
“This is the first known site of this type,” Solomon said. He has added that similar fluid seepage sites may exist nearby, although they are difficult to detect from the ocean surface.
Significant fluid leakage in central Oregon may explain why the northern part of the Cascadia subduction zone off the Washington coast is believed to be more tightly locked or coupled than the southern section off the Oregon coast.
“Pythias Oasis provides a strange window to the processes at work in the deep seafloor, and its chemistry suggests that this fluid comes from near the plate boundary,” said co-author Deborah Kelley, UW professor of oceanography.
