Originally Posted by Roland Deschain
However, even if it is in the Gulf there is a great deal of "space" in the Gulf apparently without any islands (save perhaps for the ones which I reference in my post above). Actually, it seems like there should be an island somewhere around the intersection of 25N 90W the islands I reference above would only be about a 100 miles South of that perfect "centralized" location.
It's hard to do this type of discussion w/o a reference, so may I refer you to http://gulfmex.org/map.htm
If you notice both the physical relief/reef location map at the top of the page (reefs marked in orange) and the depth contour map that's second on the page (you can then DL a larger, more detailed version from NOAA) You will see that indeed the shallower continental shelf of the Yucatan peninsula almost
but not quite makes it to the middle of the Gulf. The Alacrán Reefs are just about as far into the Gulf area as you can get in and have
islands or cays. (BTW under the latter layers of sediment, that is where you'd find the north edge of the Xichulub formation, the presumptive impact scar of the Really Big Rock from 65M years ago).
Actually, an island in dead center of open deepwater is not
the norm. Oceanic islands require volcanic/tectonic activity in the middle of the sea. Say, a long-duration volcanic hotspot, as in Hawaii, or a tectonic-plate separation or impact zone, as in Iceland. There you get rock formations that may eventually break the surface, and even if the volcanic/tectonic formation does not quite make it, or gets eroded away, if the water's warm enough corals may build upon it and emerge, as in Micronesia. If in the relief map you look south of Cuba, you see a deep undersea trench. That's where the Caribbean Plate bangs against the North America Plate and v-v. That collission creates the conditions that form the Antilles.