Michael:

> It's like one of these old sleight-of-mind maths puzzles from
> Scientific American. Where did the extra high seas come from?
> The two extra patches could only be claimed by Peru (in the north)
> and Chile (in the south), but the boundaries are drawn so as to
> prevent that happening, blocking off Peru and Chile from their little
> patch of claimable ocean outside the EEZs of Chile and Argentina
> respectively. So I guess the high seas *have* pushed a bit shorewards
> in Peru and Chile, though it feels odd to say that, given that the
> relevant patches of high sea are offshore from Chile and Argentina!

but grant please help me understand this too

I've attached a little sketch of the situation on the border between
Peru and Chile. The 1952 treaty border is defined all the way out to
200nm, and it follows a line of latitude. This means it is 45 degrees or
so away from being perpendicular to the point of inflection of a very
concave coast. So the outer limit of Peru's EEZ hits the border line at
a point very different from the juncture with Chile's EEZ. South of the
border there is sea theoretically claimable by Peru because it is less
than 200nm from Peru's coast, but unclaimable by the terms of the treaty
which limits Peru's claims to sea that is north of the limiting latitude.
A similar situation prevails in the islands at the southern tip of South
America, where a treaty line is drawn that isn't equidistant from
Chilean and Argentinian land - here, Chile loses out.
As you say, the line-of-latitude maritime boundary between Peru and
Ecuador is bound to have a similar effect, but much smaller, since it is
approximately perpendicular to the convex coast at that point - the
details of baselines in the Gulf of Guayaquil will have a major
influence there, I think.

Grant