Submarine Mass Movements in the Law of the Sea
Presented by Dr. David MOSHER on 23 Sep 2013 from 17:15 to 19:15
Type: Poster presentation
Session: Poster session
Article 76 of the United Nations Convention on the Law of the Sea delineates a number of approaches that a nation may employ to determine its’ outer jurisdictional limits beyond 200 nautical miles. In these scenarios, the “foot of the continental slope” is a critical metric. Article 76 defines the “foot of the continental slope” rather vaguely: “In the absence of evidence to the contrary, the foot of the continental slope shall be determined as the point of maximum change in the gradient at its base”. Geomorphologic complexity or low gradients (<1º) of continental slopes rarely permits a ready determination of the maximum change in gradient; particularly at a position that a geologist might qualitatively recognize as the base-of-slope zone. Recognizing that submarine mass movement is a slope process that also influences the shape of the continental margin, several nations have successfully argued that the downslope termination of MTD’s assist in distinguishing the continental slope from the rise and abyssal plain. Over segments of their margins, countries such as Ireland, Norway, New Zealand, French Guyana and Canada identified the extent of surficial MTD’s to help delineate the base of slope zone within which the foot of the continental slope is chosen. From the foot of the continental slope, a country may measure 60 nautical miles outboard to determine its’ outer jurisdictional limit, or it may measure outboard to a point where sediment thickness is 1% of the distance from the foot-of-slope; whichever is greater. The outer limit cannot exceed 350 nautical miles from the baseline (its legally defined coast) or 100 nautical miles from the 2500 m isobath.