<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). The Gulf of Mexico is one of the most important offshore petroleum production regions in the world, comprising one - sixth of the United States' total production . </P> <P> The International Hydrographic Organization defines the southeast limit of the Gulf of Mexico as follows: </P> <P> A line leaving Cape Catoche Light (21 ° 37 ′ N 87 ° 04 ′ W ﻿ / ﻿ 21.617 ° N 87.067 ° W ﻿ / 21.617; - 87.067) with the Light on Cape San Antonio in Cuba, through this island to the meridian of 83 ° W and to the Northward along this meridian to the latitude of the South point of the Dry Tortugas (24 ° 35'N), along this parallel Eastward to Rebecca Shoal (82 ° 35'W) thence through the shoals and Florida Keys to the mainland at eastern end of Florida Bay, all the narrow waters between the Dry Tortugas and the mainland being considered to be within the Gulf . </P> <P> The consensus among geologists who have studied the geology of the Gulf of Mexico is that before the Late Triassic, the Gulf of Mexico did not exist . Before the Late Triassic, the area now occupied by the Gulf of Mexico consisted of dry land, which included continental crust that now underlies Yucatán, within the middle of the large supercontinent of Pangea . This land lay south of a continuous mountain range that extended from north - central Mexico, through the Marathon Uplift in West Texas and the Ouachita Mountains of Oklahoma, and to Alabama where it linked directly to the Appalachian Mountains . It was created by the collision of continental plates that formed Pangea . As interpreted by Roy Van Arsdale and Randel T. Cox, this mountain range was breached in Late Cretaceous times by the formation of the Mississippi Embayment . </P>

Where is the continental shelf in the gulf of mexico