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What is the continental shelf?

The continental shelf is the submerged prolongation of a coastal nation’s land territory. Under customary international law, as reflected in Article 76 of the Law of the Sea Convention, this maritime zone consists of the seabed and subsoil that extends to the outer edge of the continental margin, or to a distance of 200 nautical miles if the outer edge of the continental margin does not extend up to that distance. The continental shelf is an important maritime zone that holds many resources and vital habitats for marine life.

What is the extended continental shelf (ECS)?

The ECS is that portion of the continental shelf beyond 200 nautical miles from shore. The rules for defining the outer limits of the ECS come from of Article 76 of the Law of the Sea Convention. Knowledge of the exact extent of the U.S. ECS and an improved understanding of its resources will promote economic prosperity and enhance stewardship of our natural resources.

What sovereign rights do coastal States have over the continental shelf?

The sovereign rights and jurisdiction of a coastal State are reflected in the Law of the Sea Convention and relate to the following activities:

  • Exploration, exploitation, conservation, and management of non-living resources of the seabed and subsoil of the continental shelf, such as ferromanganese crusts, ferromanganese nodules, gas hydrate deposits, and petroleum
  • Exploration, exploitation, and management of living, “sedentary species” of the continental shelf, such as clams, crabs, corals, scallops, sponges, and mollusks
  • Marine scientific research on the shelf
  • Construction, operation and use of artificial islands, installations and structures on the shelf
  • The delineation of the course for laying pipelines on the shelf
  • Drilling on the continental shelf for any purpose
  • Prevention of marine pollution in connection with some activities on the shelf

What is the difference between the continental shelf and the EEZ?

The continental shelf and the exclusive economic zone (EEZ) are distinct maritime zones. The continental shelf includes only the seabed and subsoil; whereas the EEZ includes the water column. Also, while the maximum extent of the EEZ is 200 nautical miles, the continental shelf may extend beyond 200 nautical miles from the coastline, depending on the depth, shape, and geophysical characteristics of the seabed and sub-sea floor. The ECS is, therefore, not an extension of the EEZ. Some of the sovereign rights that a coastal State may exercise in the EEZ, especially rights to the resources of the water column (e.g., pelagic fisheries), do not apply to the ECS.

Where is the United States’ ECS and how large is it?

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 several offshore areas, including 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.  The United States may also have ECS in other areas, and the U.S. ECS Project continues to collect additional data and undertake new analysis in a range of areas.

Why is determining the limits of the U.S. continental shelf important now?

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. The collection and analysis of the data necessary to establish the outer limits of the U.S. ECS also provides a better scientific understanding of our continental margins.

How much are the resources in the United States’ extended continental shelf worth?

The ECS is a very large area and very limited data have been collected to make any estimates on the potential value of resources. Given the likelihood of ferromanganese crusts, ferromanganese nodules, gas hydrate deposits, and petroleum reservoirs on or beneath the ECS, it is likely the resources are worth many billions if not trillions of dollars.

Are there additional resource management plans once the ECS outer limits are established? Will the U.S. issue lease blocks, for instance?

Additional decisions about management or exploration of ECS resources are not expected to be made until after the United States determines the extent of its ECS.

What is the Commission on the Limits of the Continental Shelf (CLCS)?

The CLCS is an expert body established by the Law of the Sea Convention. It consists of 21 members, elected by those States that are party to the Convention. Members of the CLCS are experts in geology, geophysics, or hydrography and serve in their personal capacities. The CLCS examines coastal States’ ECS submissions and makes recommendations to the submitting States. If a coastal State establishes its ECS outer limits on the basis of CLCS recommendations, those outer limits are “final and binding,” as provided for under paragraph 8 of Article 76 of the Convention. The CLCS’s mandate also includes providing scientific and technical advice, if requested by a coastal State. While the CLCS meets at the United Nations Headquarters in New York, it is an independent entity created under the Convention. The Commission’s website is available here .

Do the rights of the United States over its continental shelf depend upon accession to the Law of the Sea Convention or receiving recommendations from the CLCS?

Even for non-Parties to the Law of the Sea Convention, customary international law, as reflected in the Convention, confers rights and obligations relating to the continental shelf on a coastal State. This view is well supported in international law. The International Court of Justice, for instance, has already declared Article 76(1) to have the status of customary international law (Nicaragua v. Colombia, 2012). Article 76(1) provides that the continental shelf extends to “the outer edge of the continental margin or to a distance of 200 nautical miles,” whichever is further. Paragraphs 2 through 7 of Article 76 set forth the detailed rules for determining the precise outer limits of the continental shelf in those areas where the continental margin extends beyond 200 nautical miles from shore. Like other countries, the United States is using Paragraphs 1 through 7 of Article 76 to determine its continental shelf limits, and considers these provisions to reflect customary international law. As a matter of customary international law, the United States also respects the continental shelf limits of other countries that abide by Article 76.

Can the CLCS determine maritime boundaries that have not yet been established between neighboring countries?

No. The CLCS has no mandate to establish maritime boundaries or resolve boundary disputes between neighboring countries, nor can it make any decisions that will prejudice the future resolution of such maritime boundaries. Any boundary disagreements must be resolved between the States themselves. The focus of the CLCS’s work is to review the data and other materials submitted by coastal States and make recommendations in accordance with Article 76 of the Convention.

What other countries have ECS in the Arctic? Will any of these countries have overlapping ECS with the United States?

We believe each of the five Arctic coastal States (Canada, Denmark, Norway, Russia, and the United States) has ECS in the Arctic Ocean. Four (Russia, Norway, Denmark, and Canada) have made submissions to the CLCS that pertain to their respective ECS areas in the Arctic.

The United States has potentially overlapping ECS areas with two countries in the Arctic: Russia and Canada. The United States and the Soviet Union (now Russia) agreed to a maritime boundary (including in the Arctic) in 1990. In determining its ECS limits, Russia has respected this agreement, which continues to be provisionally applied pending its entry into force. The United States is taking the same approach. Canada and the United States have not yet established a maritime boundary in the Arctic.

Does the fact that the United States and Canada have yet to define a maritime boundary in the Beaufort Sea/Arctic Ocean affect the ECS areas for both countries?

No. The United States and Canada have cooperated extensively to collect the data necessary to define the continental shelf in the Arctic Ocean. The areas where the continental shelf of the United States and Canada overlap will not be fully known until both countries determine the extent of their ECS in the Arctic Ocean. Once those areas are identified, the United States and Canada will address the maritime boundary on a bilateral basis at an appropriate time.

How does Russia’s ECS affect the United States’ ECS?

Russia has not asserted ECS in any areas that might be considered part of the U.S. ECS. The United States and the Soviet Union agreed to a maritime boundary (including in the Arctic) in 1990. While this treaty was approved by the U.S. Senate in 1991, it has not been approved by Russia’s Duma. Nevertheless, both sides continue to provisionally apply this boundary treaty, pending its entry into force, and the Russian submission to the CLCS respects this maritime boundary.

What effect did Russia’s flag planting on the seabed of the North Pole in August, 2007 have on its ECS?

Russia’s expedition to plant a flag on the seabed of the North Pole in August 2007 has no legal effect.

Map of the Extended Continental Shelf

ECS Map 2022 V3

U.S. Department of State

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