Through the camera eyes of the undersea vehicle Jason, scientists were investigating a quietly bubbling pit on the side of a large volcano on the seafloor south of Japan in April. Then the volcano erupted.
Jason’s cameras captured the pit, 50 feet (15 meters) in diameter, spewing huge billowing clouds of gas and spitting rocks and red lava. A seafloor hydrophone deployed nearby captured the eruption’s throaty roar. It was the closest scientists have been to an erupting submarine volcano and the first time they had made concurrent visual and audio observations of a deep-sea volcano in action.
“There were some scary moments,” said Will Sellers, an expedition leader from Woods Hole Oceanographic Institution, who guided the robotic vehicle Jason via a fiber-optic cable tethered to a research ship 1,800 feet (550 meters) above. “There was a significant amount of gas coming up out of the pit. You could only imagine what it would have been like at the surface, if it wasn’t under that kind of pressure (from the tons of seawater above). It would have been huge. You wouldn’t have been able to stand anywhere near it.”
“The common reaction was, ‘Are you sure we should be here?’ ” he said. “It’s sitting there violently erupting away, and really, you got the impression that this thing is so unpredictable.”
‘Pushing the envelope of exploration’
Sellers recalled that several times the vehicle was “chased away” by enormous white and yellow clouds of gas.
“There were lava bombs as big as your head,” he said, describing globs of semi-molten sulfur. “We came up with several (stuck) in the frame of the vehicle. Fortunately they cooled enough by the time they got up to us.”
“I don’t think any one of us suspected the full magnitude of the discoveries we were to make,” Robert Embley, chief scientist on the research cruise, wrote in an online summary of the spring expedition.
“We really pushed the envelope of exploration in one of Earth’s most extreme environments,” said Embley, who is a geophysicist with the National Oceanic and Atmospheric Administration’s Pacific Marine Environmental Laboratory. “It is unlikely that a similar eruption on a volcano above sea level could have been observed and sampled as thoroughly as we were able to do.”
Because they had visited the volcano twice before and because the gas was venting and not building up pressure, scientists knew that it was a viable place to safely observe and sample an active submarine volcano, Embley said.Volcanic gases were clearly visible under water in streams of bubbles and multicolored plumes.
Most of the time, “Jason could hover about 10 feet away and watch for hours,” said Oregon State University geologist Bill Chadwick, who took part in the expedition. “You could never do that on land.”
And then … the stench
During one of four days spent at the volcano, scientists used Jason to explore a boiling sulfur lake with a temperature measuring 387°F (197°C). As they maneuvered Jason away from the edge, the vehicle broke through a wafer-thin crust into a molten pool of sulfur, dipping Jason’sback end inside. The dip caused the 4-ton vehicle to immediately gain about 80 pounds (36 kilograms) in solidified sulfur that clung to the vehicle’s rear like yellow cement.
“We were struggling to fly around because the vehicle had picked up so much weight,” Sellers said. “We did some spins trying to wash it off. It was kind of wishful thinking, a ‘Hail Mary’ maneuver, … but there’s no manual for this. So we just kind of made it up as we went along.”
They recovered the vehicle but then faced a new challenge: the stench of fresh sulfur. Months after the cruise, WHOI engineer Bob Elder still wrinkles his nose recalling the rotten egg odor that “made the whole ship smell like a cesspool.”
“The smell almost knocked everybody on the deck,” Sellers said. “As you can imagine, it got into Jason’s every nook and cranny.” Elder said. Graduate students, scientists, and members of the Jason team volunteered to chip and power-wash pounds of the smelly stuff from the vehicle.
“The eruption certainly was the frosting on the cake for the cruise, and one of the coolest, most dramatic things I’ve seen on the bottom of any ocean,” said Elder, who has participated in 81 research expeditions in his 19-year career.
Funding for Robert Embley’s research was provided by the NOAA Ocean Exploration Program.