Maritime Boundaries

Image Credit: Riccardo Pravenotti,GRID-Arendal (2010).

UNCLOS provides the basis on which the ocean is divided into a range of different jurisdictional zones, which give states different legal rights and obligations.

Baseline: Each coastal state defines a baseline along its coast. This marks the line from which other boundaries are measured, and usually encloses narrow bays and inlets.
Territorial Sea: The area within 12 nautical miles from the baseline is sovereign territory of the state (though foreign vessels are allowed innocent passage or transit).
Contiguous Zone: Beyond the territorial sea, states can claim a contiguous zone of another 12 nautical miles, in which they have certain rights of control to prevent infringements of the law within its territory.
Exclusive Economic Zone (EEZ): A coastal state can claim a 200-mile wide EEZ, within which it has control over all economic resources of the water column and seabed, from fish to fossil fuels.
High Seas: The water column beyond EEZs is termed the High Seas, which are ABNJ.
Extended Continental Shelf:
- In physical geography, the scientific term “continental shelf” refers to shallow submerged areas of continental crust between the coastline and the shelf break (the start of the continental slope, where the seabed drops off steeply towards the continental rise and oceanic abyss beyond).
- UNCLOS allows coastal states to claim exclusive access to economic resources of the seabed (e.g. mining, fossil fuels) of any declared 200 mile EEZ, even if the physical extent of the continental shelf is less than that. If the physical shelf, shelf slope and continental rise extend beyond 200 nautical miles from the baseline, coastal nations can put forward a claim for a legally defined Extended Continental Shelf within which they retain exclusive access to the resources of the seabed, but not of the water column above it (up to a maximum of 350 nautical miles from the baseline).
Areas Beyond National Jurisdiction: Marine ABNJ comprise the High Seas (waters beyond EEZs) and the seabed beyond EEZ and any Extended Continental Shelf limits (known as “the Area”).

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