Under Article 76 of The United Nations Convention on the Law of the Sea (UNCLOS; U.N. 1997), coastal states may, under certain circumstances, gain sovereign rights over the resources of the seafloor and subsurface of “submerged extensions of their continental margin” beyond the recognized 200 nautical mile (nmi) limit of their Exclusive Economic Zone (EEZ). The establishment of an “extended continental shelf” (ECS) under Article 76 involves the demonstration that the area of the ECS is a “natural prolongation” of a coastal state’s territorial landmass and then the application of a series of formulae and limit lines that are based on determination of the “foot of the slope,” (defined in Article 76 as the maximum change in gradient at it’s base), the underlying sediment thickness, and the locations of the 2500 m isobath and the 350 nmi line from the territorial sea base line. Although the United States has not yet acceded to the UNCLOS, increasing recognition that implementation of Article 76 could confer sovereign rights over large and potentially resource-rich areas of the seabed beyond its current 200 nautical mile (nmi) limit has renewed interest in the potential for accession to the treaty and spurred U.S. efforts to map area of potential “extended continental shelf”.


Center for Coastal and Ocean Mapping

Publication Date


Journal or Conference Title

U.S. Hydrographic Conference

Conference Date

May 11 - May 14, 2009

Publisher Place

Norfolk, VA, USA


Hydrographic Society of America

Document Type

Conference Proceeding