Continental Shelf and the Exclusive Economic Zone
The continental shelf is the shallow seabed extending from a coast to the shelf break. Narrow and wide shelves, the Article 76 outer limit, how it differs from the EEZ, and neighbouring seas.
The continental shelf is the shallow underwater extension of the land, running from the coast out to the shelf break where the seabed suddenly steepens. A narrow shelf means deep water close to the coast, and a wide one means shallow seabed far from land.[2] To a lawyer the term means the area where a coastal state holds sovereign rights over seabed and subsoil resources. Under the UN Convention on the Law of the Sea (UNCLOS) it reaches at least 200 nautical miles from the baselines, and where conditions are met it can extend to 350 nautical miles or to 100 nautical miles beyond the 2,500 metre isobath.[1] The two definitions need not point to the same place.
The Geological Shelf
The shelf slopes gently away from the coast, usually at around 0.5 degrees. The shelf break comes at about 140 metres, a remarkably even depth that probably reflects past ice ages, and beyond it the continental slope averages about 3 degrees.[2]
| Feature | Value |
|---|---|
| Total area | About 27 million km², around 7% of the ocean surface |
| Average width | About 80 km (57 km in one compilation) |
| Mean width at active margins | 31 km |
| Mean width at passive margins | 88 km |
| Widest example | Siberian Shelf, about 1,500 km |
| Depth at the break | About 140 m |
Source: Wikipedia, Continental Shelf, including the compilation by Harris and colleagues.[2]
The width depends on the type of margin. Passive margins, such as most Atlantic coasts, have broad shallow shelves. At active margins earthquakes move sediment into deep water, leaving shelves that are narrow and steeper. Beyond the slope lie the continental rise and the ocean floor, and shelf, slope and rise together make up the continental margin.
Some 60 to 70% of shelf sediment is relict, laid down during the last ice age when the sea stood 100 to 120 metres lower, and new sediment builds up at 15 to 40 centimetres per thousand years. Shelf seas cover around 8% of the ocean surface but support 15 to 20% of global primary production.[2] That is why so much of the world's fishing happens there.
Narrow and Wide Shelves
A narrow shelf means the seabed drops away close to the coast, and a wide one means shallow water continues far from land. The world average of about 80 km gives a yardstick. Off Chile and western Sumatra, where an oceanic plate dives beneath the continent, there is almost no shelf at all, and along parts of California it is under 1 km wide. North of Siberia it exceeds 1,000 km.[2][13]
The Black Sea shows both cases: the shelf narrows off Anatolia and spreads wide in the Gulf of Odessa and the Sea of Azov.[14] Shelves also tend to be narrow where mountains run parallel to the coast, as they do along Türkiye's Black Sea and Mediterranean shores.
How the Legal Concept Developed
The concept entered law with the Truman Proclamation of 1945, in which the United States claimed the resources of the shelf next to its coast. Others followed. The 1958 Geneva Convention on the Continental Shelf used a test of 200 metres' depth or exploitability, and as technology advanced the exploitability test became hard to pin down.[3]
In the North Sea Continental Shelf judgment of 20 February 1969, the International Court of Justice said boundaries should leave each party the areas forming the natural prolongation of its land territory. It held that equidistance was not a rule of customary law and that boundaries should be agreed according to equitable principles.[4] The current text is Part VI of the 1982 UNCLOS.
Article 76 and the Outer Limit
Article 76 defines the shelf as the seabed and subsoil beyond the territorial sea, following the natural prolongation of the land to the outer edge of the continental margin, or out to 200 nautical miles where the margin ends sooner.[1] Up to 200 miles the entitlement does not depend on the geology. Where the margin runs further, a two step calculation applies.
| Step | Rule |
|---|---|
| Outer edge of the margin (either) | Points where sedimentary rock thickness is at least 1% of the shortest distance to the foot of the slope, or points no more than 60 nautical miles from the foot of the slope |
| Maximum limit (either) | 350 nautical miles from baselines, or 100 nautical miles from the 2,500 metre isobath |
| Submarine ridges | Limit of 350 nautical miles |
| Drawing the line | Straight lines no longer than 60 nautical miles |
Source: UNCLOS, Article 76.[1]
A worked figure helps. For a point 150 nautical miles from the foot of the slope, the 1% test needs at least 1.5 nautical miles of sediment. At 1,852 metres to the mile, that is about 2,780 metres of sedimentary rock. The other limits convert just as easily: 200 nautical miles is about 370 km and 350 nautical miles about 648 km.
A state submits its data for limits beyond 200 miles to the UN Commission on the Limits of the Continental Shelf (CLCS). Limits set on the basis of the Commission's recommendations are final and binding. The Commission's records list 98 submissions and 11 revised submissions, the first from Russia on 20 December 2001 and number 98 from Chile on 18 November 2025.[1][5] Article 76 has no bearing on delimitation between neighbouring states.
Rights of the Coastal State
| Article | Content |
|---|---|
| 77 | Exclusive sovereign rights to explore and exploit, independent of occupation or proclamation. Resources are mineral and other non-living resources and sedentary species. |
| 78 | The status of the water and air above is unchanged, and navigation must not be unjustifiably impeded. |
| 79 | All states may lay cables and pipelines, with the coastal state's consent to pipeline routes. |
| 81 | The coastal state alone authorises drilling for any purpose. |
| 83 | States with opposite or adjacent coasts delimit by agreement to reach an equitable solution. |
| 85 | The coastal state may exploit the subsoil by tunnelling. |
Source: UNCLOS, Part VI.[1]
Payments for Production Beyond 200 Miles
Article 82 attaches a payment to non-living resources produced beyond 200 miles. The first five years of production are free. In the sixth year the rate is 1% of the value or volume of production, rising by a point a year to 7% in the twelfth year and staying there. Resources used in production are excluded, and a developing state that is a net importer of the mineral is exempt. Payments go through the International Seabed Authority to states parties.[1]
The 2023 Nicaragua and Colombia Judgment
In its judgment of 13 July 2023 the International Court of Justice held that, under customary law, an entitlement beyond 200 miles cannot extend within 200 miles of another state's baselines. The Court rejected Nicaragua's request on delimitation by 13 votes to 4, and having reached that conclusion it did not need to address the article 76 criteria.[6]
Shelf and Exclusive Economic Zone Compared
Within 200 miles the two largely overlap, but their legal character is different.
| Continental shelf | Exclusive economic zone (EEZ) | |
|---|---|---|
| Covers | Seabed and subsoil | Water column, seabed and subsoil |
| Arises | Without proclamation (Article 77) | Must be declared by the state |
| Maximum breadth | 200 nautical miles, further on conditions | 200 nautical miles (Article 57) |
| Resources | Non-living resources and sedentary species | All natural resources including fish, plus energy from water, currents and winds |
| Other states' rights | Navigation, cables and pipelines | Navigation, overflight, cables and pipelines (Article 58) |
Source: UNCLOS, Parts V and VI.[1][7]
Fishing shows the difference most clearly. In the EEZ the coastal state sets the allowable catch and must give others access by agreement to any surplus it cannot harvest.[7] A shelf right does not reach the fish in the water above. Articles 74 and 83 use the same delimitation formula: agreement under international law, an equitable solution, Part XV dispute procedures if talks fail, and provisional arrangements in the meantime.
Türkiye and Neighbouring Seas
Türkiye is not a party to UNCLOS.[8] Shelf delimitation has long been disputed in the Aegean and the eastern Mediterranean. What follows reports the positions the parties have stated and does not assess them. How such disputes end depends on agreement between states or international adjudication.
In the Aegean, Greece brought proceedings against Turkey at the International Court of Justice on 10 August 1976, and on 19 December 1978 the Court found it lacked jurisdiction.[9] No shelf boundary has been concluded there. In the Black Sea, Türkiye and the Soviet Union agreed a shelf boundary in 1978, and Türkiye declared an EEZ by Council of Ministers Decision 86/11264 of 5 December 1986.[10]
In the eastern Mediterranean, Türkiye and Libya's Tripoli-based Government of National Accord signed a maritime memorandum on 27 November 2019, and Greece and Egypt concluded their own EEZ agreement in August 2020. Türkiye defends its memorandum and regards the Greece-Egypt deal as null and void. Greece, Egypt, Cyprus and the European Union regard the Türkiye-Libya text as contrary to international law, with Greece arguing that the Turkish and Libyan coasts are neither opposite nor adjacent.[11][12] Libya's eastern-based House of Representatives adopted the memorandum on 20 October 2026, so the question remains live.[12]
Economic Weight of the Shelf
A large share of offshore oil and gas is produced in shelf waters, with drilling rigs and oil wells working under the coastal state's authority in article 81. Submarine cables and pipelines cross the shelf as well. In the Arctic, retreating sea ice has given outer limit submissions added interest. Fuel supply is a separate matter from the shelf regime, and details of supply by location are on the ports page.
Frequently asked questions
What is the continental shelf?
The shallow underwater extension of the land. In law, the area where a coastal state holds sovereign rights over seabed resources.
How wide is the continental shelf?
About 80 km on average. There is almost no shelf off Chile, and north of Siberia it exceeds 1,000 km.
How far can a continental shelf extend?
UNCLOS gives at least 200 nautical miles. Where conditions are met the limit is 350 nautical miles or 100 nautical miles beyond the 2,500 metre isobath.
How does the shelf differ from the EEZ?
The shelf covers the seabed and subsoil and needs no proclamation. The EEZ also covers the water, includes fishing rights and must be declared.
Is Türkiye a party to UNCLOS?
No. Türkiye does not appear as a party in UN records.
Sources
- United Nations. Convention on the Law of the Sea, Part VI, Articles 76 to 85, 1982.
- Wikipedia. Continental Shelf. Used as a secondary source.
- United Nations. Geneva Convention on the Continental Shelf, 1958, CLCS Guidelines; United States. Proclamation 2667 (Truman), 1945, secondary account.
- International Court of Justice. North Sea Continental Shelf, Judgment, 20 February 1969, summary.
- Commission on the Limits of the Continental Shelf. Submissions, Through the Secretary-General.
- International Court of Justice. Question of the Delimitation of the Continental Shelf between Nicaragua and Colombia beyond 200 Nautical Miles, Judgment, 13 July 2023.
- United Nations. Convention on the Law of the Sea, Part V, Articles 56, 57, 58, 61, 62 and 74, 1982.
- United Nations. Chronological Lists of Ratifications, UNCLOS, 2026.
- International Court of Justice. Aegean Sea Continental Shelf (Greece v. Turkey), Judgment, 19 December 1978.
- Kure Ansiklopedi. Türkiye'nin Deniz Yetki Alanları; studies on maritime jurisdiction published on Dergipark.
- Wikipedia. Libya (GNA)-Turkey Maritime Deal. Used as a secondary source; Ahram Online, Greek City Times and To Vima reports, 2020-2026.
- Enterprise. East Med Maritime Borders Deepen a Regional Schism, 23 October 2026.
- National Geographic Society. Continental Shelf, encyclopedic entry.
- Kure Ansiklopedi. Karadeniz.
