RIDGES CHAPTER 7 Harald Brekke Categories of ridges

RIDGES (CHAPTER 7) Harald Brekke

Categories of ridges in article 76 • Oceanic ridges of the deep ocean floor (paragr. 3) – excluded from the continental margin • Submarine ridges (paragraph 6) – maximum limit of 350 nautical miles for continental shelf limit • Submarine elevations that are natural components of the continental margin (paragraph 6) – maximum limit for continental shelf in accordance with general provision (paragraph 5)

Oceanic ridges • Oceanic spreading ridges • Other ridges of the deep ocean floor composed of oceanic basaltic rocks – Transform fault ridges – Other ridges of tectonic origin – Hot spot ridges – Ridges formed at oceanic plate boundaries

Earth’s surface

Submarine ridges • ”The Commission feels that the provisions of paragraphs 3 and 6 may create some difficulties in defining ridges for which the criterion of 350 M in paragraph 6 may apply on the basis of the origin of the ridges and their composition. ” (Para. 7. 2. 6. , CLCS/11)

Submarine ridges (continued) • Article 76 makes no systematic reference to the different types of the earth’s crust, but refers to: – ”the natural prolongation of … land territory” – ”the submerged prolongation of the land mass” • These terms are neutral with regard to crustal types in the geological sense (Para. 7. 2. 9. , CLCS/11)

Submarine ridges (continued) • ”…. Therefore, the Commission feels that geological crust types cannot be the sole qualifier in the classification of ridges and elevations of the sea floor into the legal categories of paragraph 6 of article 76, even in the case of island States. ” (Para. 7. 2. 9. , CLCS/11)

Submarine ridges (continued) • ”Therefore, the Commission feels that in cases of ridges its view shall be based on such scientific and legal considerations as natural prolongation of land territory and land mass, morphology of ridges and their relation to the continental margin as defined in paragraph 4. ” (Para. 7. 2. 10. , CLCS/11)

Islands and ridges Some ridges (including active spreading ridges) may have islands on them. In such cases it would be difficult to consider that those parts of the ridge belong to the deep ocean floor. (Para. 7. 2. 8. , CLCS/11)

Submarine elevations • In active margins, any crustal fragment or sedimentary wedge that is accreted to the continental margin should be regarded as a natural component of that continental margin. (Para. 7. 3. 1. , CLCS/11)

Submarine elevations (continued) • In passive margins, seafloor highs that are formed by the process of breakup of the continent should be regarded as natural components of the continental margin where such highs constitute an integral part of the prolongation of the land mass. (Para. 7. 3. 1. , CLCS/11)

Arctic Ocean Shelves IBCAO Jakobsson et al. 2000.