About the Extended Continental Shelf Project

The U.S. Extended Continental Shelf Task Force directs and coordinates the Extended Continental Shelf Project, an effort to delineate the U.S. continental shelf beyond 200 nautical miles.

The U.S. Extended Continental Shelf Task Force is an interagency body, chaired by the Department of State with co-vice chairs from the National Oceanic and Atmospheric Administration and the Department of the Interior.  Ten additional agencies participate in the Task Force:   the U.S. Geological Survey, the Executive Office of the President, the Joint Chiefs of Staff, the U.S. Navy, the U.S. Coast Guard, the Department of Energy, the National Science Foundation, the Environmental Protection Agency, BOEMRE, and the Arctic Research Commission.

  • Executive Office of the President seal
  • Department of State seal
  • NOAA seal
  • Department of Interior seal
  • USGS seal
  • Coast Guard seal
  • BOEMRE seal
  • nsf seal
  • Department of Energy seal
  • Joint Chiefs of Staff seal
  • Navy seal
  • epa seal
  • logo
Six areas where the U.S. likely has an extended continental shelf and nine areas in which the U.S. may have an extended continental shelf.

Six areas where the U.S. likely has an extended continental shelf and nine areas in which the U.S. may have an extended continental shelf. Click image for larger view.Credit: UNH/NOAA

Where does the U.S. have an ECS?

There are six areas where the U.S. likely has an extended continental shelf (ECS): the Atlantic Margin, Arctic Ocean, Bering Sea, off the west side of Guam/Northern Mariana Islands, and in two areas in the Gulf of Mexico.  There are nine areas in which the U.S. may have an extended continental shelf:  the Gulf of Alaska, the western end of the Aleutian Islands, the Northern Mariana Islands, Hawaii's Necker Island, Johnston Atoll, Kingman Reef and Palmyra Atoll, and three areas off the U.S. west coast.

Preliminary studies have indicated that the U.S. ECS likely totals at least one million square kilometers -- an area about twice the size of California or nearly half the Louisiana Purchase.  As additional data are collected and existing data analyzed, we will begin to come to a more definitive conclusion as to the extent of the U.S. ECS.

Why do it and what's there?

The U.S., like other countries, has an inherent interest in knowing, and declaring to others, the exact extent of our sovereign rights in the ocean. Specifically, a nation 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.

Defining those rights in concrete geographical terms provides the specificity and certainty necessary to protect, manage, and/or use those resources.  And international recognition is important in establishing the necessary stability for development, conservation and protection of these areas.

Because most of the ocean -- especially the deep ocean -- is unexplored, we are unsure exactly what the sea floor looks like. Given the size of the U.S. continental shelf, the resources we might find there may be worth many billions if not trillions of dollars.

 

A country may use the sediment thickness formula or the bathymetric formula to define the outer limits of its continental

A country may use the sediment thickness formula or the bathymetric formula to define the outer limits of its continental shelf. Click image for larger view.Credit: continentalshelf.gov

 

The continental shelf off Los Angeles, California

A country may use either constraint line to define the outer limits of its continental shelf: either 350 nautical miles seaward of the baseline, or 100 nautical miles seaward of the 2,500-meter depth contour (isobath).
Click image for larger view.

Credit: continentalshelf.gov

How is an ECS determined?

Determining the extent of the continental shelf is a bit different than other maritime zones, such as the territorial sea or the exclusive economic zone, because it is not simply a matter of distance from  the shoreline.

Under customary international law, as reflected in the Convention on the Law of the Sea, every country automatically has a continental shelf out to 200 nautical miles from its shore (or out to a maritime boundary with another country). In some cases, a country can have a continental shelf beyond 200 nautical miles if it meets certain criteria. Typically, the portion of continental shelf beyond 200 nautical miles is called the "extended continental shelf” or simply the ECS. Keep in mind this legal definition of the continental shelf is not the same as what a geologist would call a continental shelf.

The rules for defining the ECS are based in international law, specifically the 617 words of Article 76 in the Convention on the Law of the Sea.  A country can use one of two formulas in any combination to determine the edge of its ECS. The Convention also says there are two constraint lines that those two formulas cannot extend past. Here, too, a country can use any combination of those constraint lines to maximize its shelf.

There are two primary datasets that a country needs to collect to determine the two formula lines and the constraint lines. The first is bathymetric data that provides a three-dimensional map of the ocean floor. 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 information on the thickness of the sediments and the characteristics of the geologic layers that are stacked on top of one another.