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What is the U.S. ECS Project?

The work to delineate the U.S. extended continental shelf (ECS) is coordinated by the ECS Task Force, an interagency body of the U.S. Government.  The ECS Task Force is responsible for coordinating the collection and analysis of all relevant data and preparing the necessary documentation to establish the outer limits of the U.S. ECS in accordance with international law.  The U.S. ECS Project Office is located at the National Oceanic and Atmospheric Administration’s (NOAA) National Centers for Environmental Information in Boulder, Colorado.

The Department of State, U.S. Geological Survey (USGS), and NOAA are the agencies that handle the majority of the work of the ECS Project.  The Department of State chairs the Task Force, leads the ECS Project Office, and manages the project’s diplomatic and legal aspects.  USGS leads the effort to collect, process, and interpret the seismic data.  NOAA leads the effort to collect, process, and analyze the bathymetric data.

Eleven other Government agencies or offices are part of the ECS Task Force:  Executive Office of the President, Joint Chiefs of Staff, U.S. Navy, U.S. Coast Guard, Department of Energy, National Science Foundation, Environmental Protection Agency, Bureau of Ocean Energy Management, Bureau of Safety and Environmental Enforcement, Arctic Research Commission, and Marine Mammal Commission.

Why do it and what’s there?

The United States, like other countries, has an inherent interest in knowing, and declaring to others, the exact extent of its ECS and thus the sovereign rights it is entitled to exercise in this part of the ocean.  Defining those limits in concrete geographical terms provides the specificity and certainty necessary to protect, manage, and use the resources of the ECS.

Consistent with international law, as reflected in the 1982 Law of the Sea Convention, the United States has sovereign rights over the resources on and under the seabed, including petroleum resources (oil, gas, gas hydrates), “sedentary” creatures (such as clams, crabs, and corals), and mineral resources, such as manganese nodules, ferromanganese crusts, and polymetallic sulfides.

Because most of the ocean — especially the deep ocean — is unexplored, we are unsure exactly what the seafloor looks like or what resources it contains.  Given the size of the U.S. ECS, the energy, mineral, and living resources may be worth many billions if not trillions of dollars.

How big is the U.S. ECS?

The U.S. ECS is approximately one million square kilometers — an area about twice the size of California or about half the size of the Louisiana Purchase. This is a significant area over which the United States may exercise sovereign rights over seafloor and sub-seafloor resources.

The United States has ECS in the Arctic Ocean north of Alaska, the Atlantic East Coast, the Bering Sea, Pacific West Coast, the Mariana Islands, and two areas in the Gulf of Mexico (map) The United States may also have ECS in other areas, and the U.S. ECS Project continues to analyze available data and undertake analysis in a range of areas.

How is an ECS determined?

Determining the extent of the continental shelf is different from determining the extent of other maritime zones, such as the territorial sea or the exclusive economic zone.  Those maritime zones are determined based on a specified distance from the U.S. baselines, effectively the shoreline.   Determining the extent of the ECS, however, requires knowledge of the geophysical characteristics of the seabed and subsoil.

Under customary international law, as reflected in the Law of the Sea Convention, every coastal State (i.e., country with a coastline) automatically has a continental shelf extending out to 200 nautical miles from its shore, or out to a closer maritime boundary with a neighboring coastal State.  In some cases, a coastal State can have a continental shelf beyond 200 nautical miles if it meets certain criteria.

The portion of the continental shelf beyond 200 nautical miles is typically called the “extended continental shelf” or simply ECS.  ECS is a term of convenience; under the Law of the Sea Convention, the term “continental shelf” includes both continental shelf within 200 nautical miles and also ECS.  Also, the Law of the Sea Convention defines “continental shelf” in legal terms, which is not the same as what a geologist would consider continental shelf.

The legal rules for determining the ECS outer limits are reflected in Article 76 in the Convention.  A coastal State can use one of two formulas in any combination to determine the outer edge of its continental margin.  Article 76 also contains two constraint lines.  If the formula lines extend past the constraint lines, a State can use any combination of those two constraint lines to maximize its ECS.  The outer limit of the continental shelf is determined by the combined use of Article 76’s formula lines and constraint lines.  (See figures, below.)

There are two primary datasets that a country needs to collect to determine the formula lines and the constraint lines. The first is bathymetric data that provides a map of the depths of the ocean floor, an important component for both formula lines and one of the constraint lines. The second is seismic reflection data that provides a cross-section view of what’s beneath the ocean floor.  From that cross-section view, scientists can derive the thickness of the sediments under the seafloor, an important component for the second formula.

a coastal State can use the 60 M formula or the sediment thickness formula to determine the outer edge of its continental margin
there are two constraint lines, one that is 350 nautical miles from the baseline and one that is 100 nautical miles from the 2,500 meter isobaths

The Extended Continental Shelf

U.S. Department of State

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