--- In BoundaryPoint@yahoogroups.com, "Lowell G. McManus"
<mcmanus71496@m...> wrote:

> Continents stop where the sea begins. Such a wet tricontinental
> tripoint would be as bizarre as a dry
> Atlantic-Indian-Mediterranean tripoint in the middle of Africa!

I suppose one could think of the triple divide between watersheds as
being a tripoint of seas on land. For its waterlogged counterpart of
continents in the sea, one could think of the tripoints of the
various continental plates. Two problems with that, though, are that
(A) there is far from a 1:1 correspondence between continents, and
(B) the border between tectonic plates is a zone, not an
infinitesimally thin line.

Here's a map:
http://geology.er.usgs.gov/eastern/plates.html

So, Europe and Asia share the same plate, but you could find an
Africa-Arabia-Eurasia trizone somewhere near the coast of Lebanon.
The Cocos-North America-Pacific trizone would be in the Gulf of
California. And there would be two Juan de Fuca-North America-Pacific
trizones, one in Northern California and one near the north end of
Vancouver Island.

This guy has a map of major triple divides in the continental U.S.:
http://www.geocities.com/CapitolHill/Lobby/3162/3RP/Maps/us_divides.ht
m

And an article about it:
http://www.custerguide.com/quillen/eqcols/1999B217.htm

A couple of trivia questions can be answered using that map:
1. What's the only Confederate state with no land that drains to the
Gulf of Mexico?
2. What's the northernmost of the 13 original states with land that
drains to the Gulf of Mexico?

Adam