The US Department released this past week the geographic coordinates defining the outer limits of the US continental shelf in areas beyond 200 nautical miles from the coast, known as the extended continental shelf (ECS). The continental shelf is the extension of a country’s land territory under the sea. Like other countries, the United States has rights under international law to conserve and manage the resources and vital habitats on and under its ECS.

The United States has ECS in seven offshore areas: the Arctic, Atlantic (east coast), Bering Sea, Pacific (west coast), Mariana Islands, and two areas in the Gulf of Mexico.

The US ECS area is approximately one million square kilometers—an area about twice the size of California. The Department of State led the ECS effort through the US ECS Task Force, an interagency body of the US Government composed of 14 agencies.

Determining the ECS outer limits requires data on the depth, shape, and geophysical characteristics of the seabed and subsoil. The National Oceanic and Atmospheric Administration (NOAA) and US Geological Survey (USGS) were responsible for collecting and analyzing the necessary data. Data collection began in 2003 and constitutes the largest offshore mapping effort ever conducted by the United States.

The United States says it has determined its ECS limits in accordance with customary international law, as reflected in the relevant provisions of the 1982 United Nations Convention on the Law of the Sea, and the Scientific and Technical Guidelines of the Commission on the Limits of the Continental Shelf.