Continental shelf II: Seafloor highs · submarine ridges, the outer limit of the continental shelf...
Transcript of Continental shelf II: Seafloor highs · submarine ridges, the outer limit of the continental shelf...
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C o n t i n e n t a l s h e l f I I : S e a f l o o r h i g h s
S c i e n t i f i c i n t r o d u c t i o nW a l t e r R o e s t , I f r e m e r, F r a n c e
M e m b e r o f C L C S ( 2 0 1 2 –2 0 1 7 )
New Knowledge and Changing Circumstances –Reykjavik – 28 and 29 june 2018
Disclaimer
“ The views expressed herein are solely
those of the author and do not necessarily
reflect the views of the Commission on the
Limits of the Continental Shelf “nor those of
any Government
204/07/2018
Introduction
• Seafloor highs are probably the most difficult
features to deal with in Article 76
• Seafloor elevations and ridges have been known
for a long time, but for many their origin,
formation and precise extent was unclear in the
late 70s, when Article 76 was developed (new
knowledge)
• Ridges are mentioned twice in Article 76, limiting
their contribution to the continental margin/shelf:
can there be exceptions ? In other words: Is a
ridge always a ridge?
• Continental margin (paragraph 4) versus
continental shelf (application of constraints) 04/07/2018 3
Article76 - Seafloor HighsParagraphs 3 and 6 mention ridges and elevations:
3. The continental margin comprises the submerged
prolongation of the land mass of the coastal State […]
shelf, the slope and the rise. It does not include the
deep ocean floor with its oceanic ridges or the
subsoil thereof.
6. Notwithstanding the provisions of paragraph 5, on
submarine ridges, the outer limit of the continental
shelf shall not exceed 350 nautical miles from the
baselines from which the breadth of the territorial sea is
measured. This paragraph does not apply to
submarine elevations that are natural components of
the continental margin, such as its plateaux, rises,
caps, banks and spurs.04/07/2018 4
Knowledge in 1978
A/CONF.62/C.2/L.98 and Add.1, 18 April 1978
Knowledge in 1978
Kerguelen Plateau
A/CONF.62/C.2/L.98 and Add.1, 18 April 1978
A/CONF.62/C.2/L.98 and Add.1, 18 April 1978
Knowledge in 1978
French Submission to the CLCS
Resolution of satellite derived bathymetry versus multi beam bathymetric data
Shelf Slope Rise Deep Ocean Floor
Excluded from the
Continental MarginContinental Margin
Deep Ocean Floor
is excluded from
the Continental
Margin
UNCLOS Article 76: the continental shelf
Shelf Slope Rise Deep Ocean Floor
Excluded from the
Continental Shelf
CLCS Guidelines - Seafloor Highs
Continental Margin
What about
Oceanic Ridges?
CLCS Guidelines - Seafloor Highs
7.1.2. Article 76 mentions three types of seafloor highs:
- Oceanic ridges of the deep ocean floor (para. 3);
- Submarine ridges (para. 6) ;
- Submarine elevations (para. 6) .
7.1.3. None of these terms is precisely defined ….
Scientific and Technical Guidelines, CLCS/11, Chapter 7
Ridges form by a variety of geological processes
Ridges formed by the sea-floor spreading and associated volcanic magmatic processes;
Ridges formed along transform faults and created as an inherent part of the sea-floor spreading process;
Ridges formed by later tectonic activity resulting in uplift of oceanic crust;
Ridges formed by volcanic activity related to the movement of crust over a hot spot;
Ridges formed by interaction of oceanic crustal plates;
Ridges formed by regional excessive volcanism related to plumes of anomalously hot mantle;
Ridges associated with active plate boundaries and the formation of island arc systems. […];
Ridges formed by rifting (extension and thinning) of continental crust. […]
Scientific and Technical Guidelines, CLCS/11, Chapter 7
Two critical questions
Since Article 76 only mentions 2 types of ridges, Oceanic Ridges (deep ocean floor?) and Submarine Ridges (restricted to 350 M):
• Can an Oceanic Ridge become a submarine ridge?– Yes, if it lies within the continental margin
• Can an Oceanic Ridge become a natural component– Yes, if it lies within the continental margin and
shares significant geological characteristics with the landmass
Two critical questions
Since Article 76 only mentions 2 types of ridges, Oceanic Ridges (deep ocean floor?) and Submarine Ridges (restricted to 350 M):
• Can an Oceanic Ridge become a submarine ridge?– Yes, if it lies within the continental margin
• Can an Oceanic Ridge become a natural component– Yes, if it lies within the continental margin and
shares significant geological characteristics with the landmass
Two critical questions
Since Article 76 only mentions 2 types of ridges, Oceanic Ridges (deep ocean floor?) and Submarine Ridges (restricted to 350 M):
• Can an Oceanic Ridge become a submarine ridge?– Yes, if it lies within the continental margin
• Can an Oceanic Ridge become a natural component– Yes, if it lies within the continental margin and
shares significant geological characteristics with the landmass
Example of Iceland
From Summary of Recommendations by the CLCS to Iceland
Geologial
continuity within
a V-
shaped area of
the Reykjanes
Ridge:
Example of
gravity data
Hey et al., 2010
FOS points accepted by Subcommission
From Summary of Recommendations by the CLCS to Iceland
Iceland in the
western and
southern parts of
the Reykjanes
Ridge
Example of Iceland• The CLCS treats Ridges on a case by case basis
• The Subcommission recognised that part of the Reykjanes Ridge was a natural component of Iceland’s continental margin (morphologically AND geologically connected)
• Therefore, the prevalent view in the Subcommission was that the depth constraint is the applicable constraint in the western and southern parts of the Reykjanes Ridge.
• The Commission concluded that the data and information contained in the Submission were inconclusive to support the western and southern parts of the Reykjanes Ridge as a natural component of the continental margin of Iceland
FOS points accepted by Subcommission
From Summary of Recommendations by the CLCS to Iceland
FOS points 03 to 08 were
accepted unanimously by the
Commission.
While some members of the
Commission accepted the
locations of the FOS points
110, 120, 23, and 145, other
members did not accept the
location of the base of the
continental slope around
them
Conclusion1. The extent and configuration of the continental margin of a
coastal state […] is determined in accordance with Article 76, paragraph 4.
2. Seafloor highs that are not enclosed by the FOS envelope are excluded from contributing to the establishment of the outer edge of the continental margin […]. However, such seafloor highs, or parts thereof, can ultimately lie within the outer edge […].
3. Seafloor highs that lie beyond the outer edge of the continental margin are considered part of the “deep ocean floor with its oceanic ridges” in the sense of Article 76, paragraph 3.
4. Classification of seafloor highs is determined on the basis of the geological characteristics of the features in addition to their already proven morphological continuity with the landmass of the coastal state.
Harald Brekke & Philip Symonds (2011): Ocean Development & International Law
Thank you!