<P> The Gulf of Mexico formed approximately 300 million years ago as a result of plate tectonics . The Gulf of Mexico basin is roughly oval and is approximately 810 nautical miles ( 1,500 km ; 930 mi ) wide and floored by sedimentary rocks and recent sediments . It is connected to part of the Atlantic Ocean through the Florida Straits between the U.S. and Cuba , and with the Caribbean ( with which it forms the American Mediterranean Sea ) via the Yucatán Channel between Mexico and Cuba . With the narrow connection to the Atlantic , the Gulf experiences very small tidal ranges . The size of the Gulf basin is approximately 1.6 million km ( 615,000 sq mi ) . Almost half of the basin is shallow continental shelf waters . The basin contains a volume of roughly 2,500 quadrillion liters ( 550 quadrillion Imperial gallons , 660 quadrillion US gallons , 2.5 million km or 600,000 cu mi ) . </P>
how many gallons of water in the gulf of mexico
660 quadrillion US gallons