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Continental Shelf Extension

The Continental Shelf Extension, foreseen in the United Nations Convention on the Law of the Sea, aims to increase the maritime territory under the jurisdiction of Coastal States. This results from the interpretation and application of legal concepts, through the acquisition of technical-scientific data (Hydrography, Geology and Geophysics) that allow defining the limit of Portugal's continental shelf beyond the 200 nautical miles measured from the coastline.

Continental Shelf Extension Criteria (CSEP)

The delineation of the outer limits is established through the application of two positive formulas and two restrictive conditions defined in article 76 of the Convention. The application of positive formulas is dependent on the determination of the points designated as the foot of slope (FOS) at the base of the slope that establishes the transition to the deep ocean floor.
The outlined outer limits must therefore comply with at least one of the following positive rules exemplified in these diagrams:

These limits will be subject to the best of the following restrictive conditions (maximum):

The application of these positive rules and restrictive conditions leads to the establishment of the outer limits of the Continental Shelf beyond 200 nautical miles, over which the coastal State may exercise sovereignty and jurisdictional rights over the marine seabed and subsoil and natural resources therein.

In the following example, the outer limit of the continental shelf of Coastal State A is defined by the red line, which results from the most favourable combination of the positive rules and restrictive conditions provided for in the Convention.

For the preparation of a Continental Platform Extension Proposal, it is necessary to compile and proceed with the acquisition of data:

  • Bathymetric, in order to evaluate the depth and shape (geomorphometry) of the seabed with high resolution;

  • Geological and Geophysical (data from reflection and refraction seismics, gravimetry and magnetism), which allow to assess the nature, geometry and origin of the seabed.


In the case of Portugal, prior to the Continental Shelf Extension Project (PEPC), the knowledge of the seabed in the areas corresponding to the EEZ was based on information acquired with simple beam probes, derived from systematic surveys carried out by the Hydrographic Institute, by foreign ships in transit or during scientific research cruises conducted in the national EEZ.
With PEPC, hydrographic surveys were carried out with multi-beam probes. These surveys represent a considerable advance, with regard to resolution, when compared to the previous situation.

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