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CIRES researchers help map one million square kilometers of new U.S. seafloor in historic project

The United States has established sovereign rights over an additional one million square kilometers of seafloor, thanks to a government-led project that included a team of CU ����Vlog�ƽ�� researchers. 

The was a collaborative, multi-agency effort to map and define the boundaries of the country’s extended continental shelf (ECS)—the portion of the continental shelf beyond 200 nautical miles from the coast. 

What is a continental shelf?

In geologic terms, continental shelves are the edges of continents that are submerged under the ocean. In legal terms, the continental shelf is the extension of a country’s land territory under the sea.  

Besides adding a million square kilometers of seafloor to the U.S.—an area roughly twice the size of California—researchers discovered interesting undersea features, including a 1,400-meter-high methane plume off the California coast. They were also able to determine the precise depth of the Challenger Deep—the deepest spot in the ocean—at 10,994 meters (36,070 feet). 

Scientists at the Cooperative Institute for Research in Environmental Sciences (CIRES) at CU ����Vlog�ƽ�� took the lead in analyzing the geophysical data used to determine and document the U.S. ECS outer limits. The U.S. Department of State those outer limits in December 2023, more than 20 years after the project began.

“We’ve established the limits of the U.S. continental shelf and it’s now up to us to explore, learn new science, and then steward, manage and help preserve these areas for future generations,” said Barry Eakins, a marine geophysicist working in NOAA’s (NCEI) who led the CIRES 
ECS team.

Charting the seafloor

In the early 2000s, government officials began planning to map and define areas where they suspected the U.S. had ECS. Data collection began in 2003 and involved mapping the seafloor topography to define where the physical continental shelf and slope end and determining sediment thickness in some areas.

The National Oceanic and Atmospheric Administration (NOAA), with help from CIRES scientists, led the seafloor mapping effort. Over the course of the project, NOAA mapped more than three million square kilometers of seafloor—an area larger than Alaska, California and Texas, combined.

With expertise in marine geophysics, data management, Geographic Information System (GIS) and cartography, Barry Eakins and his CIRES team led the effort to analyze the data collected. The monumental task involved evaluating all three million square kilometers of newly mapped seafloor and interpreting the geologic features in key areas.

The ECS Project Office used CIRES scientists’ analyses of seafloor features to determine the precise boundaries of U.S. ECS in seven different regions. Eakins said what made the project so successful was the team’s careful attention to detail; they wanted to be confident that their results would be robust and defensible, he said. 

Determining the ECS limits helps scientists understand the geologic history of remote areas of the seafloor and contributes much-needed data to the to map the entirety of Earth’s seafloor by 2030.

“The United States has established the limits of the seafloor that it has sovereign rights to, and that seafloor is still largely unknown,” Eakins said. “So, this is a tremendous opportunity to go out and explore the geologic features, the sediments that are down there, but the life that is down there as well.”