The Gulf of Mexico is a geographic area and a body of water that forms the so-called third coast of the contiguous United States. The Gulf of Mexico is surrounded on the United States side by coastlines of western and northern Florida, Alabama, Mississippi, Louisiana, and Texas. In Mexico, the Gulf is bordered by the states of Tamaulipas, Veracruz, Tabasco, Campeche, and Yucatán. The western end of the island of Cuba forms a partial barrier to the eastern Gulf of Mexico, where it joins the Caribbean Sea. The Gulf of Mexico is roughly oval-shaped with a long dimension of about 950 mi (1,500 km). The area of the Gulf of Mexico is about 615,000 square mi (1.6 million square km). For more than 500 years, the Gulf of Mexico has played a key role in the economic and political development of the United States, Cuba, and Mexico.
Historical Background and Scientific FoundationsThe Gulf of Mexico is thought to he originated about 250 million years ago with the rifting or breaking apart of the tectonic plates of North America, South America, and Africa. When these components separated, an area of ocean floor developed between North and South America, which became the basin for the Gulf of Mexico. Not long after this basin was formed, sea water access to the basin was restricted and much of the sea water evaporated. We know this because today a large part of the deeper Gulf of Mexico basin is underlain by a thick layer of salt from this evaporation event. After an early dynamic history of crustal plate movement, the Gulf of Mexico basin became a stable area of Earth's crust and has remained so ever since.
Features of the Gulf of MexicoThe Gulf of Mexico is generally characterized by wide continental shelves around most of its periphery. These shelves, where water depths are at most a few hundred feet, he been the sites of intensive oil exploration in the past and to the present. The shelves give way to continental slopes, which lead down to the deeper plain of the Gulf of Mexico floor, which is known as the Sigsbee Deep. On the northern shelf of the Gulf of Mexico, an enormous pile of sediment from the Mississippi River delta has built a feature called the Mississippi sedimentary cone. This cone extends across the continental shelf and down the continental slope in front of the mouth of the Mississippi River.
Plastic and pliable salt from deep within the Gulf of Mexico basin has been squeezed up over time due to the weight of continental shelf and slope sediments. The upward movement of this buoyant salt has formed a submarine ridge on the northern continental shelf's outer margin, which is called the Sigsbee Ridge. In addition, numerous salt domes (conical salt intrusions) rise through the continental shelf sediments and in some places on land as a result of this pressure-related salt mobilization from below.
Geological History of the Gulf of MexicoAfter salt deposition early in the Gulf's history, sediment began to gradually fill in this stable basinal area between continents. Sand, clays, and muds from the adjacent land areas of the northern Gulf of Mexico rim were continually washed into the Gulf basin by the Mississippi and other rivers. Much of this sediment came from sources in the Appalachian, Ouachita, and other adjacent uplifted mountains. In the Florida area and in the Yucatán area of Mexico, sediments of a chemical nature (calcium-carbonate precipitates and organic remains) filled in the basin.
WORDS TO KNOWRIVER DELTA: Flat area of fine-grained sediments that forms where a river meets a larger, stiller body of water such as the ocean. Rivers carry particles in their turbulent waters that settle out (sink) when the water mixes with quieter water and slows down; these particles build the delta. Deltas are named after the Greek letter delta, which looks like a triangle. Very large deltas are termed megadeltas and are often thickly settled by human beings. Rising sea levels threaten settlements on megadeltas.
SEDIMENT: Solid unconsolidated rock and mineral fragments that come from the weathering of rocks and are transported by water, air, or ice and form layers on Earth's surface. Sediments can also result from chemical precipitation or secretion by organisms.
SHORELINE: The band or belt of land surrounding a large body of surface water, such as a lake or ocean.
TECTONIC PLATE: Rigid unit of Earth's crust that moves about over geological time, merging with and separating from other tectonic plates as the continents rearrange but retaining its identity through these encounters. There are seven major tectonic plates on Earth and a number of smaller ones.
UPWELLING: The vertical motion of water in the ocean by which subsurface water of lower temperature and greater density moves toward the surface of the ocean. Upwelling occurs most commonly among the western coastlines of continents, but may occur anywhere in the ocean. Upwelling results when winds blowing nearly parallel to a continental coastline transport the light surface water away from the coast. Subsurface water of greater density and lower temperature replaces the surface water and exerts a considerable influence on the weather of coastal regions. Carbon dioxide is transferred to the atmosphere in regions of upwelling.
Starting about 160 million years ago, organic rich sediments were deposited in the Gulf of Mexico, which eventually became a key source layer for the Gulf's rich petroleum industry. Much of this petroleum became entrapped in a formation found through much of the northern Gulf rim called the Smackover Formation. Around 120 million years ago, a large reef system rimmed the western and northern Gulf of Mexico. These reefs, which were composed of now-extinct clams and associated shell fish, eventually formed some of the highly productive oil fields of eastern Mexico. Over the past 100 million years, the Gulf has remained a stable area, which is gradually being filled, mainly from the north and west, by sediment from sand- and clay-laden rivers.
Gulf of Mexico EconomicsIn addition to the oil production mentioned earlier, there is associated gas production from wells drilled into sediments of the Gulf of Mexico. Further, the Gulf has a highly valuable fishing production, both shell fish (for example, oysters) and swimming fish. The fishing industries of the Gulf coastal United States, Cuba, and Gulf coastal Mexico are supported by abundant living resources of the Gulf area. The continental margins of Florida and the Yucatán (Mexico) are situated in areas where deeper, cold, nutrient-rich waters in the Gulf rise through a process called upwelling. This provides for abundant growth of marine plankton, which in turn supports fish, shrimp, and squid harvesting.
The Gulf of Mexico has historically been an important enue for shipping and there are many key ports on the Gulf, including New Orleans, Louisiana; Houston, Texas; and others. Gulf shores are well known as resort areas in Florida, Mississippi, Alabama, and parts of the Texas coast.
Gulf of Mexico Waters and IslandsWarm waters of the Gulf of Mexico are both a blessing and a curse. They give rise to the waters of the Gulf Stream, which flows north out of the Gulf and brings warmer waters to northern areas of the Atlantic. Such waters are a key factor in the success of the tourism industry mentioned earlier. Warm waters of the Gulf help fuel the intensity of tropical storms and hurricanes, which commonly enter the Gulf from sites in the western tropical Atlantic Ocean. Gulf of Mexico hurricanes, especially some in recent years such as Katrina, are famous for their potential for hey damage and loss of life.
The Gulf of Mexico shoreline is notable for its barrier islands, which form end-to-end chains from Florida to eastern Louisiana and eastern Texas to eastern Mexico. These barrier islands are separated from the mainland by a narrow body of water such as a lagoon, bay, or estuary. Barrier islands are low-lying narrow strips of land that represent a delicate balance between sand ailability, sea level, and coastal we energy. The only parts of the Gulf shoreline that are not part of this barrier island trend are the marshy coasts of Louisiana and the Mexican coast (for example, along the Yucatán coast), where sand is not readily ailable.
Impacts and IssuesLike all bodies of water on Earth, the Gulf of Mexico responds to climatic change. For example, during times of warming climates, as today, higher sea surface temperatures cause intensification of cyclonic storms in the Gulf of Mexico. Communities and ecosystems along the Gulf of Mexico still remain especially vulnerable to disruption from storms after the record hurricane season of 2005 that included Hurricanes Katrina and Rita. The 2005 Atlantic hurricane season was the most active in recorded history. Also, sea level is rising in the Gulf of Mexico as it is globally today. Alternatively, during past times of much cooler global climates, the Gulf of Mexico was a much smaller body of water (due to lower sea level) and probably had far fewer cyclonic storms than today.
See Also Beach and Shoreline; Hurricanes; Sea Level Rise.
BIBLIOGRAPHYBooksGore, R. H. The Gulf of Mexico: A Treasury of Resources in the American Mediterranean. Sarasota, FL: Pineapple Press, 1992.
Web Sites“Gulf of Mexico Integrated Science Data Information Management System.” U.S. Geological Survey, July 25, 2007. < http://gulfsci.usgs.gov> (accessed December 3, 2007).
GulfBase: Resource Database for Gulf of Mexico Research, 2007. < http://www.gulfbase.org> (accessed December 3, 2007).
Did T. King Jr.