WOODS HOLE — As offshore wind developers run into glauconite, a mineral that presents challenges for wind turbine installation, the U.S. Geological Survey is conducting a monthslong study to identify exactly where glauconite is already known to be.
The study began in early summer, after some offshore wind developers found glauconite on parts of the seafloor they’ve leased for wind farms — a series of discoveries that The Light reported on last month. Government geologists will focus on a variety of seafloor features that might challenge renewable energy infrastructure, including shallow pockets of natural gas and underwater landslides as well as glauconite.
In the coming months, scientists will review data from the last wide-scale effort to sample the U.S. Atlantic seafloor for glauconite — which happened in the 1960s and 1970s.
“This is a study that doesn’t involve collecting new data,” said Laura Brothers, a marine geologist with the Geological Survey, in an interview with The Light. “We’re going to be combing through all the publicly available and trusted sources of data regarding things that can be hazardous for infrastructure placement and development offshore.”
The study will also examine glauconite deposits on land. “We’ll look at where glauconite is known to occur onshore and what layers of rocks are known to have it,” Brothers said, “to get the best idea we can about where it can be offshore. It’s kind of the best we can do without collecting a substantial amount of new data.”
The Geological Survey, which is the U.S. Interior Department’s science arm, will look at geological features of the continental shelf — on which more than two dozen wind projects are planned -– that may pose threats to project construction and operation.
The study will analyze the more than 20 wind farm lease sites in the Atlantic Ocean, and “characterize the geological features and physical processes that may pose hazards to infrastructure and workplace safety.”
Funding for the study comes from another Interior Department agency, the U.S. Bureau of Safety and Environmental Enforcement. A spokesperson for that agency says its agreement with the Geological Survey, signed in May, is set to conclude in November 2024. The agency declined an interview request.
At the project’s completion, the Geological Survey plans to release a report that summarizes where glauconite is found.
Developers have been collecting their own geological data, which may include discoveries of glauconite, during the survey work that precedes offshore wind turbine construction and installation. However, that data is proprietary.
The last major effort to sample the U.S. Atlantic seafloor for glauconite happened in the 1970s, after Congress in 1962 authorized the Continental Margin Program.
The study covered a range of sediments in addition to glauconite — quartz, mica, feldspar, pyrite — and was undertaken to explore the largely unexplored continental shelf. Researchers from the Geological Survey and Woods Hole Oceanographic Institution took hundreds of samples and photographs stretching from Nova Scotia to Florida.
“It was a great unknown at the time and still is to some degree,” Brothers said of the continental shelf.
In 1972, the Geological Survey published a paper on its findings.
“Very high concentrations of glauconite are found in the bight [coastal region] between New Jersey and Long Island and south of Long Island,” wrote geologist James Trumbull. “Except in the vicinity of Georges Bank, glauconite appears to be forming along the entire length of the outer continental shelf.”
In a separate paper published the same year, Woods Hole scientist John Milliman wrote Georges Bank and Nantucket Shoals are covered with “relatively stable sand containing appreciable amounts of glauconite.”
Georges Bank is farther offshore relative to where wind farms have been sited, but the Nantucket Shoals abuts planned development off the Rhode Island and Massachusetts coasts. There, two projects have confirmed the presence of glauconite.
Maps from the 1972 report provide some information about where glauconite was found.
“These areas where it is darkest, that’s the highest percentage of glauconite,” Brothers said, pointing to maps on a computer screen. “They did a suite of analysis on these samples, so this is a really important dataset at the time; it covered the whole [Atlantic] margin.”
Still, it’s a limited sampling. The researchers grabbed only the top five to eight inches of the ocean floor, and then analyzed a fraction of the sediments from those samples, said Jason Chaytor, a marine geologist who works for the Geological Survey.
Wind developers may run into glauconite feet below the seafloor’s surface. The turbine foundations will need to push through several feet of seafloor to reach required depths.
The researchers in the 1970s weren’t collecting samples to understand the geotechnical challenge caused by glauconite. “There wasn’t a thought of an offshore wind industry at that time,” Brothers said.
A paper published this year by the Bureau of Ocean Energy Management said glauconite formations are “abundant” along the continental shelf, and that wind developers will “inevitably” encounter the material during construction.
The ocean energy bureau collaborates with the safety and environmental enforcement bureau on offshore wind development, with the latter focusing on safety and environmental requirements for installation and the lifetime of the projects. Both agencies came from the splitting of one, the Minerals Management Service, in 2010 after the Deepwater Horizon oil spill.
Early this year (around the time the ocean energy bureau released its paper on glauconite), the safety bureau entertained funding a second study with the Geological Survey that would collect new data on the mineral in the Atlantic, per emails obtained by The Light through the Freedom of Information Act.
Brothers sent the agency a draft proposal for a study, called “Glauconite Hazards for Offshore Renewable Energy Installations.” One scenario in the proposal involved sampling an offshore wind lease area off the New Jersey coast owned by Attentive Energy (a developer that’s funding research into glauconite’s behavior with four other wind companies).
A spokesperson for the Bureau of Safety and Environmental Enforcement said it has not funded any other inter-agency agreements regarding glauconite. The spokesperson did not answer questions about the proposal for a second study.
Brothers said the current study is a good first step. “In general, if we were to go out to explore and find where glauconite is, I think you’d first want to do exactly what we’re doing right now, which is go through all available data,” Brothers said. “Ultimately, if you find glauconite, you’re going to need to take some samples of that seafloor.”
“Until additional data is available, that remains our best resource,” Chaytor said. “Really the only way to find it is to see it.”
The approach for mapping most sediments, he explained, involves geophysical testing and taking samples from the ocean floor.
That survey work can establish a three-dimensional view of the layers beneath. When it’s paired with physical samples like sediment cores or “grab samples,” scientists can extrapolate to a degree. If a layer that was tested contained glauconite, that layer likely contains glauconite elsewhere along the seafloor.
“We have such large outer continental shelves and they are largely unmapped by modern methods,” Brothers said. “And so it’s a tremendous opportunity to learn about all of the potential resources and uses that our shelves have. And it’s also a challenge because they are so unexplored.”
Email Anastasia E. Lennon at email@example.com.
Thank you to our sponsors
Founding benefactors: Joan and Irwin Jacobs fund of the Jewish Community Foundation, Mary and Jim Ottaway
For questions about donations, contact Chrystal Walsh, director of advancement, at firstname.lastname@example.org.
For questions about sponsoring The Light, contact Peter Andrews, director of business development and community engagement, at email@example.com.