The tectonic plate that underlies the Caribbean Sea and most of Central America. The Caribbean Plate is shaped like
an elongated letter "D", extending about 2000 km east to west between Central America, where the Cocos Plate is
subducting beneath it, and the Lesser Antilles, where the North American Plate is subducting beneath it. It
extends about 800 km from north to south between the Greater Antilles and the South American coast. At the northern end
of the eastern subduction zone, the Puerto Rico Trench is one of the deepest spots in the world ocean. The Carribean plate
appears on the ASCII map in my writeup on the Cocos Plate.
The Caribbean Plate is yet another fragment of the ancient Farallon Plate consumed by El
Norte. As North America broke away from the rest of Pangaea during the late Jurassic Period, the Farallon Plate
continuted to subduct beneath the diverging plates to the east. As with all ocean subduction zones, a volcanic
arc formed in the overriding American plates. A hot spot may have been involved as well, but the Antillean Arc built
itself up until about 100 million years ago (late Cretaceous), when the arc broke off the North American Plate and began to
subduct over it, becoming fused to the Farallon Plate. The arc then began to move raidly eastward, and a bulge in the
Farallon plate began to fill the gap between North America and South America (with some subduction under the latter).
By 70 million years ago, this bulge had broken off the Farallon Plate. A new volcanic arc (which forms Costa Rica and
Panama today) formed where the Farallon Plate subducted beneath this new "Caribbean" plate. Meanwhile the Antillean Arc
spread further and further eastward, assembling southern Mexico and Nicaragua. Pieces broke off the southern end,
forming terranes which later welded to northwestern South America, as well as the Netherlands Antilles.
Pieces of the Antillean Arc broke off the northern end of the arc, forming Jamaica, and various pieces of Hispaniola
which would assemble themselves later. The northern part of the arc advanced so rapidly that the seafloor behind couldn't
keep up. In a process called back-arc rifting, Cuba was spreading away from the plate by 60 mya. But by 50 mya, however, Cuba had collided with the Bahama Platform, ending the spread to the north. The Caribbean Plate was now trapped between North America and South America.
It is quite possible that the Antillean Arc's rapid subduction of the Atlantic Ocean floor will lead to general
retrenchment along the Atlantic coast of the Americas. That is, the Atlantic floor may break off of North and South
America and begin to subduct beneath them, beginning the closure of the Atlantic Ocean and paving the way for the formation
of the next supercontinent.
This reconstruction is due to the work of Dr. James Pindell, then at Rice University, during the late 1980's and early 1990's. His amazing series of maps at the Carribean Geology and Tectonics website (see below) depicts the formation of the Carribean region far better than any description I could give.
The Carribean Geology and Tectonics website, at
http://www.fiu.edu/orgs/caribgeol/
has everything you might want to know about Carribean geology.
Maps at
http://www.fiu.edu/orgs/caribgeol/Caribreconstr.html, if you can't navigate the frames.
James Pindell, "The Pacific Origin of the Caribbean Plate, with emphasis on Cuba", abstract at
http://www.le.ac.uk/gl/rvw1/abstract/pindell.html
A little animated movie of the Caribbean region's formation can be found at
http://www.scotese.com/caribanim.htm