When University of Washington oceanographers visited the deep-ocean Axial Volcano in late July, parts of the seafloor were still warm.
The team knew to expect changes in the mile-deep volcano 300 miles off the Oregon coast. This spring, seafloor seismometers connected to shore by a new Internet cable showed that Axial Volcano, a 3,600-foot-tall underwater volcano, started shaking April 24 and shook continuously for several days.
The recent visit, part of a larger cruise, was scientists’ first chance to see the site and explore what happened.
“It was a very large eruption,” said Deborah Kelley, a UW professor of oceanography who led the expedition on the UW’s Thomas G. Thompson research vessel. “The eruption itself was at least 7 kilometers long. We were just looking at one small lobe of this section of new ocean crust.”
The team got to explore the scene through a deep-sea cabled robot hosting cameras and sensors, ROPOS, that is lowered from the ship. ROPOS crawled up a 295-foot-thick, 2,100-foot-wide section of newly formed basalt.
During a seven-hour dive on July 28, the robotic vehicle followed a 30-degree slope up to the top of the flow. There, it was engulfed in cloudy waters and a blizzard of white material — the so-called snowblowers of organic matter created by microbes that bloom and thrive after volcanic eruptions.
“When we got up there, it was really like driving through a snowstorm,” Kelley said.
She believes bacteria that thrive off methane and sulfur were growing inside warm fluid-filled pockets and channels in the flowing lava, where the environment is rich in chemicals and gases that the microbes use for energy. What look like snowflakes actually came from white microbial mats most common where water was seeping from the lava at temperatures as warm as 64 F (18 C), compared to the near-freezing water in the surrounding deep sea.
Life had also begun growing on the surface of the new rock. Thick, orange mats of bacteria covered vast sections of the cooling lava, surrounding the white microbes.
“We really don’t know when life starts growing on the rocks, but this is just three months old and already in some places the mats are very thick, completely masking the surface of the rock below,” Kelley said.
She studies seafloor volcanoes and the mysterious life forms that inhabit these unique environments, which some scientists think may have hosted the first life on Earth.
Slabs of lava carried up to the research vessel by the robotic vehicle showed that the rock was covered with a layer of glass up to three-quarters of an inch thick, which forms when the lava cools very quickly in frigid seawater.
A student on the cruise from Grays Harbor College in Aberdeen, Washington, will study microbes on one of the samples to better understand how life colonizes a fresh lava flow. Scientists at the UW and other institutions will further analyze the samples and data to understand relationships between underwater eruptions and other environmental shifts.
“This is the third time at this volcano that we’ve seen vast expanses of microbes colonizing the cooling lava flows within a couple months of an eruption,” Kelley said, “so that relationship is probably prevalent on many underwater volcanoes.”
The UW team recovered samples and collected observations that will complement the data streaming from more than 20 sensors that are continuously recording conditions across the caldera.
The April eruption was first detected by instruments about 10 to 25 miles south of the flow, at cabled study sites at the summit and base of the volcano. Sensors recorded the vibrations, seafloor movement and sounds during the event. UW-installed cabled sensors recorded about 8,000 small earthquakes during that time, and a seafloor drop of up to about 8 feet at the summit of the volcano, southwest of the flow. The first seafloor-mapping data and video from the research cruise confirm that the volcano erupted a significant volume of lava during the event: the third eruption since 1988.
The recent visit was part of a National Science Foundation cruise, from July 4 to August 7, to conduct the first annual maintenance of this cabled deep-sea observatory off the Pacific Northwest coast, a major component of the NSF Ocean Observatories Initiative.
Another NSF-sponsored cruise, led by Bill Chadwick of Oregon State University, will leave Aug. 14 and will focus on exploring the site of the eruption.
“We really just got a glimmer of what it was like,” Kelley said. “There are a lot of places to explore to figure out what was happening during this impressive eruption.”
Source: University of Washington