PORTLAND, Ore. (KOIN) – Warm fluid is shooting “like a firehose” into the Pacific Ocean off the Oregon Coast and researchers believe it’s regulating pressure on the Cascadia Subduction Zone, the offshore fault that has the potential to cause a magnitude-9 earthquake in the Pacific Northwest.
It’s something scientists have likely never discovered before, but researchers from the University of Washington stumbled upon the underwater spring unexpectedly in 2014 while delayed aboard a boat for a different oceanography mission.
The boat of scientists was about 50 miles off the coast of Newport when the ship’s sonar showed unexpected bubbles about three-quarters of a mile beneath the ocean’s surface.
In 2015, investigators researched the source of the bubbles and found an underwater spring shooting chemically distinct water up from the seafloor. They called it Pythias Oasis.
UW believes the underwater spring is sourced from water that’s located 2.5 miles beneath the seafloor at the plate boundary and that it serves to regulate stress on the offshore fault.
“They explored in that direction and what they saw was not just methane bubbles, but water coming out of the seafloor like a firehose. That’s something that I’ve never seen, and to my knowledge has not been observed before,” said Evan Solomon, a UW associate professor of oceanography who co-authored a paper published on the spring.
Throughout their research, Solomon and first author Brendan Philip found the fluid leaving the seafloor is 16 degrees Fahrenheit and warmer than the surrounding seawater. They believe the water comes directly from the Cascadia megathrust in the subduction zone, where temperatures are estimated to be 300 to 500 degrees Fahrenheit.
They said the fluid seeping out of Pythia’s Oasis is unique for the Cascadia Subduction Zone and includes extreme enrichment of boron and lithium and depletion of chloride, potassium, and magnesium.
Soloman said the new seeps aren’t related to geologic activity but instead occur near vertical faults that crosshatch the Cascadia Subduction Zone.
Scientists say losing fluid through these faults is important because it lowers the fluid pressure between the sediment particles, therefore increasing the friction between the oceanic and continental plates – which are the two plates that meet at the Cascadia Subduction Zone.
“The megathrust fault zone is like an air hockey table,” Solomon said. “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.”
He also compared the fluid released from the fault zone to leaking lubricant, which is bad news for earthquake hazards. UW said less lubricant means stress can build to create a damaging earthquake.
Solomon said a significant fluid leak off the Central Oregon coast could explain why the northern portion of the Cascadia Subduction Zone, off the Washington coast, is believed to be more strongly locked than the southern section near Oregon.
Pythia’s Oasis is the first known seep location of its kind. Solomon said similar fluid seep sites may exist nearby, but they’re hard to detect from the ocean’s surface.
“Pythia’s Oasis provides a rare window into processes acting deep in the seafloor, and its chemistry suggests this fluid comes from near the plate boundary,” said co-author Deborah Kelley, a UW professor of oceanography.
She said this suggests the nearby faults regulate fluid pressure and megathrust slip behavior along the central Cascadia Subduction Zone.