672 
We are advised informally by scientists of the U. S. Geological Survey 
that about 7.5 percent of the area of the ocean floor is encompassed by 
the 200 meter isobath. Similarly, about 16 percent of the area of the 
ocean floor is included within the 2,000 meter contour. While no com- 
parable estimates are available for the 2,500 meter isobath, adjacent to 
the continents, an estimate has been made for the 3,000 meter isobath 
(world-wide, not merely adjacent to the continents), and the percentage 
of the area of the world’s ocean basins found to be included by that iso- 
bath is about 25 percent. It would appear, therefore, that if coastal state 
mineral jurisdiction is equated geographically with the submerged con- 
tinental land mass (the continental margin, including the geological 
concepts of the continental shelf, the continental slope, and the landward 
portion of the continental rise), and if this, in turn, is equated provi- . 
sionally with an average water depth of 2,500 meters, adjacent to the 
continents, the result is that substantially less than 20 percent of the 
area of the world’s sea-beds is within the exclusive mineral jurisdiction 
of the coastal states, and more than 80 percent of the total sea-bed area 
is outside the coastal regime with respect to mineral development. 
In particular instances, as where there is a very narrow or ill-defined 
continental margin, it may be equitable to regard the limit of adjacency 
as extending beyond this line. In such situations, the adjacency concept 
gives the coastal state exclusive mineral jurisdiction in an area of 
deep ocean floor which is reasonable with regard to all relevant circum- 
stances. In general, a reasonable measure of this jurisdiction might well 
be the average width of the continental margins of the world’s oceans, 
or approximately 100 miles, though there might be situations, as in the 
case of some of the smaller seas, in which a different standard would be 
more appropriate. 
Special problems may also occur with respect to islands. 
On the view proposed above, a sufficiently definite seaward limit for 
the exclusive jurisdiction of the coastal state may be persuasively derived 
from the language of the Convention as it now stands. Any doubts or 
differences can be resolved on an ad hoc basis as they arise. Hence 
there would seem to be at this time no need to consider possible changes 
in the Convention in anticipation of the time when it becomes open to 
proposals for revision in June 1969. Likewise, it does not now seem 
desirable to urge the convening of a.new international conference, which 
might well raise more problems than it would settle. 
Nevertheless, in view of current debate over the limit of coastal state 
jurisdiction under the present Convention, it may be desirable that this 
