Three kilometers under the sea

Dr. Patricia Gregg leads an expedition to explore underwater volcanoes.
written by Logan Weeter

In case you think the days of charting unmapped territory on Earth belong to the history books, let us introduce you to Patricia Gregg, a professor of geology who, along with several others from Illinois, recently returned from a deep sea expedition about 750 miles off the west coast of Mexico.

Professor Patricia Gregg heads up the Gregg Lab at Illinois, studying volcano geophysics & geodynamics.

Only about 10 percent of the ocean seafloor has been mapped. If that alone fails to trigger the imagination, you might consider Gregg’s videos detailing deep sea life such as tripod fish and albino octopuses, or the strangely beautiful and (literally) chilling particulars of what it’s like to sink to depths of almost three kilometers below sea level.

This past November, Gregg led a multi-institutional expedition called the Off-axis Seamount Investigations at Siqueiros, or the OASIS Expedition. The team, which included geology professor Craig Lundstrom and four graduate students from Illinois, sought to investigate a chain of underwater volcanoes located in the central east Pacific Ocean to better understand how new seafloor is created.

Alvin in the field. This is the submersible’s first ever selfie. (Underwater photos in this story taken using WHOI MISO facility deep-sea camera systems and Alvin cameras. ©Copyright WHOI.)

The month-long journey was spent on the R/V Atlantis, a research vessel owned by the U.S. Navy and operated by Woods Hole Oceanographic Institution. To explore the sea bottom, the researchers descended to the depths in Human Operated Vehicle Alvin, a unique deep-sea submarine that has been helping scientists make critical observations since the 1960s.

The team also used a high-tech autonomous vehicle, called Sentry, to produce high-resolution maps of their volcano targets.

The purpose of the successful journey—which Gregg prepared three years for—was to investigate undersea volcanoes that had never before been explored. Gregg specializes in volcano geophysics, focusing on tectonically and volcanically active mid-ocean ridges that chain together all across Earth’s sea floor. It’s a relatively new field of study, as the mid-ocean ridge systems were only discovered in the mid-20th century.

“Most of the volcanic activity on our planet is underwater,” Gregg said. “At mid-ocean ridges, we know a lot about the volcanoes that are being created on the ridge, but as soon as you traverse off the ridge, there are many other volcanoes, and we don’t have a lot of data for them.”

The team from Illinois set out with others from a variety of institutions, including Woods Hole Oceanographic Institution, the University of Florida, Boise State University, the National Science Foundation (which provided funding for the expedition), the U.S. Geological Survey, Lamont Doherty Earth Observatory at Columbia University, Sapienza University of Rome, and the Carnegie Department of Terrestrial Magnetism.

The OASIS team had three goals in mind. First, they wished to map the area of that seafloor in in detail to fill critical observational gaps. Second, they wanted to better understand how magma is moving though the Earth’s mantle to get back to the ridge where it erupts to create new oceanic crust.

Third was the desire to “combine observations of geochemistry and geophysics,” according to Gregg, to learn more about “not only the types of rocks that erupted on the seafloor, but their geochemical signature, because we can use the chemistry of those lavas to trace back where they came from, and combine that information with our geophysical observations to create a better 3D model for what’s happening.”

The researchers focused on a part of the seafloor that has never been explored—and, due to limited resources and the high demand for Alvin, may never be explored again.

“You can imagine that there are many targets that we want to utilize Alvin for,” Gregg said, “So going back to the same target requires a very specific reason. Unless there is some very compelling reason that you would go back to that exact same site, chances are that Alvin won’t go back.”

Even though the purpose of the trip was to observe submarine volcanoes, the researchers encountered a plethora of odd biology along the way, from deep-sea sponges and coral, to sea spiders and so-called dumbo octopuses. This area of the seafloor is home to many unique creatures. Some observations led Gregg and her team to conclude that the volcanoes may have been active as recently as the past decade, providing the level of heat and water chemistry that would attract the creatures that were found.