Applying the criteria in Article 76 of the Law of the Sea Convention requires data on the morphology of the seafloor and, in some areas, the thickness of the underlying sediment. For this reason, the ECS Project has conducted field programs necessary to collect bathymetric and seismic data.

Bathymetric Data

Bathymetric data are collected using state-of-the-art multibeam echosounders that provide a three-dimensional map of the surface of the seafloor. These data are important for applying the criteria in Article 76, including identifying the foot of slope and 2,500 meter (m) isobaths (i.e., depth contours).

Bathymetric data collection for the ECS Project is coordinated through the Center for Coastal and Ocean Mapping/Joint Hydrographic Center (CCOM/JHC), a cooperative partnership between NOAA and the University of New Hampshire. Since 2002, CCOM/JHC has mapped more than two and a half million square kilometers of the ocean floor, an area the size of Alaska and Texas combined. These data were collected on thirty-one cruises in ten regions totaling nearly two-and-a-half years of sea time (Table 1.1).

ECS Region Dates Ship Bathymetric Data
(sq km)
Arctic Aug 30-Sep 10, 2003 USCGC Healy 10,000
Oct 6-26, 2004 USCGC Healy 20,000
Aug 16-Sep 14, 2007 USCGC Healy 70,000
Aug 14-Sep 5, 2008 USCGC Healy 34,600
Sep 5-Oct 1, 2008 USCGC Healy 29,158
Aug 7-Sep 16, 2009 USCGC Healy 66,135
Aug 3-Sep 4, 2010 USCGC Healy 47,663
Aug 15-Sep 28, 2011 USCGC Healy 58,000
Aug 26-Sept 27, 2012 USCGC Healy 68,600
Sep 19-Oct 6, 2016 USCGC Healy 14,000
Atlantic Aug 23-Sep 18, 2004 USNS Henson 255,000 (total all three legs)
Sep 25-Oct 20, 2004 USNS Henson
Oct 29-Nov 29, 2004 USNS Henson
Apr 29-May 30, 2005 USS Pathfinder 148,500 (total both legs)
Jun 5-23, 2005 USS Pathfinder
May 1-31, 2008 Roger Revelle 124,216
July 3-17, 2012 Ronald H. Brown 69, 287
July 30-Aug 29, 2015 Marcus G. Langseth 157,166
Bering Sea July 7-28, 2003 Davidson 21,000
Gulf of Alaska Jun 24-Jul 29, 2005 Kilo Moana 321,466
Gulf of Mexico Jun 21-Jul 8, 2007 Northern Resolution 32,300
Johnston Atoll Aug 9-22, 2014 Kilo Moana 97,250
Kingman Reef & Palmyra Atoll May 12-Jun 16, 2010 Kilo Moana 107,435
Nov 20-Dec 20, 2015 Kilo Moana 164, 200
Jan 12-Feb 9, 2016 Ron Brown 166,756
Mendocino Ridge May 5-26, 2009 Okeanos Explorer 14,136
Sep 23-Oct 11, 2014 Atlantis 103,074
Necker Island Aug 21-Sep 3, 2009 Okeanos Explorer 18,207 (total both legs)
Sep 12-26, 2009 Okeanos Explorer
Jul 31-Aug 10, 2011 Kilo Moana 47,394
Nov 15-Dec 21, 2017 Kilo Moana 149,770
Northern Mariana Islands and Guam Oct 15-Nov 15, 2006 USNS Bowditch 92,111
Nov 16-Dec 17, 2007 USNS Bowditch 92,151
Aug 6-Sep 5, 2010 USNS Sumner 187,503
Sep 24-Oct 21, 2010 USNS Sumner 156,023
Sep 14-Oct 13, 2016 Fugro Supporter 102,440

Seismic Data

The second primary dataset is seismic data, which provides information on the depth, thickness, geometry, and other characteristics of the sediments lying on the seafloor.  The ECS Project requires seismic data to derive the thickness of the sediment for those regions where the sediment thickness formula in Article 76 applies.

Seismic data is collected by a sound source towed behind the ship which emits acoustic energy at constant time or distance intervals. The transmitted energy is reflected or refracted from boundaries between various geologic layers (such as sedimentary horizons) and received in an array of hydrophones towed behind the ship called a seismic streamer or in a self-contained instrument deployed in the water behind the vessel (sonobuoy) or resting on the seafloor (ocean bottom seismometer).  The signals are recorded in digital form and stored on high-speed computers for subsequent processing, analysis, mapping, interpretation, and display.

Seismic data collection for the ECS Project is coordinated through the U.S. Geological Survey.  Seismic data collection has been completed in the Arctic, Atlantic, Bering Sea, and Gulf of Alaska (Table 1.2).  USGS made significant efforts to minimize the impact of seismic data collection on living resources through careful planning, obtaining the applicable authorizations, and following mitigation strategies.

Seismic data in the Arctic Ocean was conducted in a cooperative effort with Canada.  The U.S. Coast Guard Cutter (USCGC) Healy collected multibeam bathymetric data and created a straight and open path through the ice for the Canadian Coast Guard ship Louis S. Saint Laurent, which followed collecting seismic reflection and refraction data with sensors towed behind the stern of the ship.

ECS Region Dates Ship Seismic Data
(linear km)
Arctic Aug 30-Oct 11, 2007 CCGS Louis S. St-Laurent 2,987
Aug 21-Oct 3, 2008 CCGS Louis S. St-Laurent 4,217
Aug 6-Sep 16, 2009 CCGS Louis S. St-Laurent 4,069
Aug 4-Sep 15, 2010 CCGS Louis S. St-Laurent 3,600
Aug 18-Sep 29, 2011 CCGS Louis S. St-Laurent 1,437
Aug 11-Sept 3, 2016 CCGS Louis S. St-Laurent 629
Bering Sea Aug 10-Sep 2, 2011 Marcus G. Langseth 2,200
Gulf of Alaska Jun 6-26, 2011 Marcus G. Langseth 3,200
Atlantic Aug 21-Sept 13, 2014 Marcus G. Langseth 2,760
Apr 10-May 3, 2015 Marcus G. Langseth 3,005

Training and Data Support

The U.S. ECS Project has assisted more than 30 countries in their efforts to delineate their extended continental shelves. The Project has also benefitted from the experiences and views of other countries and experts.

Over the past 10 years, the National Centers for Environmental Information (NCEI, formerly the National Geophysical Data Center) has provided bathymetric and seismic data directly to at least 20 countries. Data has been provided directly to: Bangladesh, Costa Rica, Cuba, Kiribati, Malaysia, Papua New Guinea, The Bahamas, Trinidad and Tobago, United Kingdom, Vietnam, and South Africa. NCEI also provided data to the United Nations Environment Programme (UNEP) and its efforts to assist other countries including: Cabo Verde, Chile, Ecuador, Madagascar, The Maldives, Mauritania, The Gambia, Guinea, Guinea-Bissau, Senegal, Sierra Leone, Somalia, and Vanuatu. Many other countries have downloaded data from NCEI servers in support of their ECS delineation efforts.

In September 2015, the U.S. ECS Project hosted a week-long training session on how to delineate an ECS and compile the necessary analysis and documentation. The training was conducted in cooperation with the UN Division for Ocean Affairs and the Law of the Sea (DOALOS) and included present and former members of the Commission on the Limits of the Continental Shelf. Nearly 50 ECS specialists from numerous countries of the Americas and Pacific islands participated.

Cooperative Data Collection with Canada in the Arctic Ocean

Much of the data necessary to delineate the continental shelf of the United States and Canada in the Arctic Ocean was collected cooperatively in a two-ship operation.

The U.S. Coast Guard Cutter (USCGC) Healy collected multibeam bathymetric data and created a straight and open path through the ice for the Canadian Coast Guard ship Louis S. Saint Laurent, which followed collecting seismic reflection and refraction data with sensors towed behind the stern of the ship.

This two-ship approach, conducted over four field seasons, collected more than 13,000 linear kilometers of seismic data; this joint work was both productive and necessary in the Arctic’s difficult and varying weather and ice conditions. This collaboration saved millions of dollars for both countries, provided data both countries need, ensured that data are collected only once in the same area, and increased scientific and diplomatic cooperation.

U.S. Department of State

Welcome to the new

Our new design makes it easier to find and learn about the State Department’s programs and services—from passports and visas to learning how U.S. diplomacy benefits the American people.