Science

OASIS Expedition Uses Sophisticated Tech to Probe the Ocean Floor

submersible being lowered into the ocean

Less than 5 percent of ocean terrain is 3D mapped, but scientists are using deep submersible vehicles, drones and more to probe the sea bed and discover what lies below the surface.

Centuries ago, explorers took to the seas, searching for new territories and hidden passages. Along the way, they discovered islands and continents, as well as new species, societies and knowledge.

All of Earth’s landmasses are already mapped, but less than 5 percent of the ocean floor has been charted. A new generation of explorers is hoping to discover the mysteries of the great blue unknown.

Trish Gregg on OASIS expedition
Trish Gregg is leading the OASIS Expedition to explore underwater volcanoes. Photo by Joyce Riha Linik.

Patricia “Trish” Gregg is one such explorer, a kind of part-time Vespucci when she’s not teaching volcanology and related subjects at the University of Illinois at Urbana-Champaign (UIUC).

Gregg recently set course for the middle of the Pacific Ocean, where she is leading a team of scientists on a five-week research expedition called OASIS (Off-Axis Seamount Investigations at Siqueiros). The goal is to explore, and three-dimensionally map, a never-before-visited underwater string of volcanoes called 8⁰ 20’N Seamount Chain.

“Volcanic melt is difficult to trace in continental studies because the crust is 30 to 60 kilometers thick,” said Gregg. She said the crust in mid-ocean ridges is much thinner – about 6 km thick – making it easier to study how magma is created in the mantle and, once it forms, how it moves through the mantle to erupt on the seafloor.

“Tracing that back to how volcanoes form on continents is important,” she said, noting that such data can help scientists better predict volcanic eruption behavior wherever it occurs on Earth.

“Plus, it has other planetary applications. Mercury, Mars, Venus. Io, one of the moons of Jupiter. They all have active volcanoes. The moon once did. If we understand how melt propagates, that can be extrapolated to other places as well.”

OASIS expedition submersible
Photo of the Sentry courtesy of Woods Hole Oceanographic Institution.

Deep Sea Science

Gregg, who developed a study on what triggers the eruptions of supervolcanoes, has spent years planning this expedition.

With 80 percent of volcanoes on Earth under water and scattered around the globe, Gregg explained why she chose this particular site.

“There was a concerted effort in the late 1990s and early 2000s to focus research expeditions on the Pacific mid-ocean ridge axis and do very detailed mapping and investigation, to get to know the site over time, and to observe the temporal evolution, Gregg said.

“Scientists recorded multiple volcanic eruptions and observed the interactions between the eruptions and the sea creatures – how the surrounding biology adapts and comes back after being decimated,” she explained.

The next step, Gregg said, is to understand the bigger picture, including the Seamount volcano chain that stretches out hundreds of miles from the mid-ocean ridge axis.

Gregg’s team includes experts in volcanology, geophysics, geochemistry and petrology. A biologist is also on call should unusual plants or animals be encountered.

The Technological Dream Team

On board the Atlantis, a highly sophisticated research vessel owned by the U.S. Navy and operated by Woods Hole Oceanographic Institution (WHOI), Gregg’s team of scientists employs a range of high-tech equipment in their underwater investigations.

Sentry is an autonomous underwater vehicle – essentially a drone – capable of explorations down to 6,000 meters. The vehicle can be pre-programmed to travel for hours at a time, creating maps of the seafloor and taking digital imagery along the way. It can navigate extreme terrain such as underwater mountains, steep slopes and volcano calderas.

the Alvin submersible
Photo of Alvin by Joyce Riha Linik.

But the rock star of this expedition – and all underwater exploration – is Alvin, the human-operated deep submergence vehicle that has racked up over 4,700 dives over the last five decades. Alvin has been instrumental in finding a misplaced hydrogen bomb, discovering deep-sea hydrothermal vents and exploring the wreck of the Titanic.

The vehicle gives two scientists at a time (along with the pilot) a front-row seat to underwater science, in depths as low as 4,500 meters and dives up to 10 hours. First commissioned in 1964, Alvin has remained state-of-the-art due to numerous upgrades and overhauls through the years.

Alvin can float in place in the water, maneuver over rugged terrain, or sit on the ocean floor. It can collect data in the water column, produce maps and collect digital photos and video. Two robotic arms can be directed to manipulate instruments and obtain samples which are placed in a basket configured for each dive.

scientists prepare for the expedition
Chief Scientist Trish Gregg (left) prepares for the expedition with WHOI scientists Adam Soule and Anna-Louise Reysenbach. Photo by Joyce Riha Linik.

For scientists jazzed about the deep ocean, it’s a dream come true to catch a ride in Alvin.

“I’m still pinching myself,” said Gregg. “I’ve been inspired by these amazing scientists who’ve used these technologies. And one day I wake up and I’m one of them.”

For Gregg, one role model was marine geophysicist Deborah K. Smith, who was chief scientist on Gregg’s first WHOI expedition as a recent college grad back in 2001.

In addition to Sentry and Alvin, the Multidisciplinary Instrumentation in Support of Oceanography (MISO) TowCam, an underwater camera lowered and towed from the ship, is an essential part of the oceanic investigation.

“TowCam is often overlooked because it is not as sexy as Alvin or Sentry,” said Gregg, “but its utility should not be underestimated.”

The TowCam can be dropped for relatively quick glimpses of what lies below to determine where to send Alvin. Similarly, Sentry can be sent out to collect imagery before Alvin’s next dive is planned.

During the OASIS expedition, Alvin will make an estimated 17 dives; Sentry, 15 to 17.

The scientists, too, work a finely orchestrated schedule. Three teams work eight-hour shifts, 24/7, to make maximum use of research time at sea.

As imagery and samples come in from Alvin, Sentry and TowCam, the science team processes the data. This includes analyzing all samples in a fully-equipped lab set up by the scientists themselves prior to their departure from Manzanillo, Mexico. Their gear — including microscopes, assays for testing lava, and more — was shipped in advance to ensure they’d have the equipment they need.

Whatever the expedition finds, it will bring scientists a step closer to understanding volcanic activity, whether in the ocean, on the Earth’s landmasses, or in the vast reaches of space.

Plus, new three-dimensional maps of this underwater mountain chain will be invaluable to researchers and oceanic travelers going forward.

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