Researchers from the University of Washington have discovered a unique underwater spring called Pythia's Oasis located approximately 50 miles off Newport, Oregon. According to a study published in Science Advances, the spring is a source of warm and chemically distinct liquid that emerges from water 2.5 miles beneath the seafloor at the plate boundary, regulating stress on the offshore fault. The researchers made the discovery while exploring the seafloor using sonar during a weather-related delay for a cruise aboard the RV Thomas G. Thompson. The observation showed that the fluid leaving the seafloor is 9 degrees Celsius warmer than the surrounding seawater, and it comes straight from the Cascadia megathrust, where temperatures are estimated to be between 150 to 250 degrees Celsius.

The discovery is significant since the Cascadia Subduction Zone is an offshore fault that has the potential to unleash a magnitude-9 earthquake in the Pacific Northwest. The researchers believe that the feature they discovered could provide vital clues to earthquake hazards. The fault zone is like an air hockey table where fluid pressure plays a vital role. High fluid pressure means there's less friction, and the two plates can slip, leading to a quake. In contrast, lower fluid pressure means that the two plates will lock, creating stress that can build up and create a damaging earthquake.

The Pythias Oasis provides a rare window into processes occurring deep in the seafloor, and its chemistry suggests that the fluid comes from near the plate boundary. Co-author Deborah Kelley, a UW professor of oceanography, said that the nearby faults regulate fluid pressure and megathrust slip behavior along the central Cascadia Subduction Zone. The researchers believe that this is the first-known site of its kind, and similar fluid seep sites may exist nearby, although they are hard to detect from the ocean's surface.