Gulf of Mexico in 3D perspective.
The 'Gulf of Mexico' is the ninth largest
body of water in the world. It is an ocean basin largely surrounded by the
North American continent and the island of
Cuba. It is bounded on the northeast, north and northwest by the
Gulf Coast of the United States, on the southwest and south by
Mexico, and on the southeast by
Cuba. The shape of its basin is roughly circular and approximately 810
nautical miles (1,500 km) wide and filled with sedimentary rocks and debris. It connects with the
Atlantic Ocean through the
Florida Straits between the U.S. and Cuba, and with the
Caribbean Sea (with which it forms the
American Mediterranean Sea) via the
Yucatan Channel between Mexico and Cuba.
Tidal ranges are extremely small due to the narrow connection with the ocean.
The gulf basin is approximately 615,000
mi² (1.6 million km²). Almost half of the basin is shallow intertidal waters. At its deepest it is 14,383 ft (4,384 m) at the
Sigsbee Deep, an irregular trough more than 300
nautical miles (550 km) long.
It was probably formed approximately 300 million years ago as a result of the seafloor sinking.
[1] There is evidence that the
Chicxulub Crater was formed when a large
meteorite hit the earth 65 million years ago which may have led to the
Cretaceous–Tertiary extinction event.
[2]
History
Formation
Little is known about the geologic history of the Gulf of Mexico Basin before
Late Triassic time. Some authors have postulated the presence of a basin in the area during most of
Paleozoic time, but most evidence seems to indicate that Paleozoic rocks do not underlie most of the Gulf of Mexico basin and that the area was, at the end of Paleozoic time, part of the large supercontinent of
Pangea, the result of the collision of several continental plates.
[3]
The present Gulf of Mexico basin is believed to have had its origin in Late Triassic time as the result of rifting within the
North American Plate at the time it began to crack and drift away from the
African and
South American plates. Rifting probably continued through Early and Middle
Jurassic time with the formation of "stretched" or "transitional"
continental crust throughout the central part of the
basin. Intermittent advance of the sea into the continental area from the west during late Middle Jurassic time resulted in the formation of the extensive
salt deposits such as the
Brine pool. It appears that the main drifting episode, during which the
Yucatan block moved southward and separated from the North American Plate and true oceanic crust formed in the central part of the basin, took place during the early
Late Jurassic, after the formation of the salt deposits.
3
Since Late Jurassic time, the basin has been a stable geologic province characterized by the persistent subsidence of its central part, probably due at first to thermal cooling and later to sediment loading as the basin filled with thick prograding clastic wedges along its northwestern and northern margins, particularly during the
Cenozoic.
3
To the east, the stable
Florida platform was not covered by the sea until the latest Jurassic or the beginning of
Cretaceous time. The Yucatan platform was emergent until the mid-Cretaceous. After both platforms were submerged, the formation of
carbonates and
evaporites has characterized the geologic history of these two stable areas. Most of the basin was rimmed during the Early Cretaceous by carbonate platforms, and its western flank was involved during the latest Cretaceous and early
Tertiary in a compressive deformation episode, the
Laramide Orogeny, which created the
Sierra Madre Oriental of eastern
Mexico.
3
Today, there are 7 main areas of the gulf:
3
★
Gulf of Mexico Basin, which contains the
Sigsbee Deep and can be further divided into the continental rise, the
Sigsbee Abyssal Plain, and the
Mississippi Cone.
★
Northeast Gulf of Mexico, which extends from just east of the
Mississippi Delta near
Biloxi to the eastern side of
Apalachee Bay.
★
South Florida Continental Shelf and Slope, which extends along the coast from
Apalachee Bay to the
Straits of Florida and includes the
Florida Keys and
Dry Tortugas.
★
Campeche Bank, which extends from the
Yucatan Straits in the east to the
Tabasco-
Campeche Basin in the west and includes
Arrecife Alacran.
★
Bay of Campeche , which is an isthmian
embayment extending from the western edge of
Campeche Bank to the offshore regions just east of
Veracruz, Mexico.
★
Eastern Mexico Continental Shelf and Slope, which is located between Veracruz to the south and the
Rio Grande to the north.
★
Northern Gulf of Mexico, which extends from
Alabama to the
U.S.-
Mexico border.
European exploration
Although
Christopher Columbus was credited with the founding of the Americas, the ships in his four voyages never reached the Gulf of Mexico. Instead, Columbus sailed into the
Caribbean around
Cuba and
Hispaniola.
The first
European exploration of the Gulf of Mexico was
Amerigo Vespucci in
1497. He followed the coastal land mass of
central America before returning to the
Atlantic Ocean via the
Straits of Florida between
Florida and
Cuba. In his letters, Vespucci described this trip, and once Juan de la Cosa returned to
Spain, a famous world map, depicting Cuba as an island, was produced.
In
1506,
Hernán Cortés took part in the conquest of
Hispaniola and
Cuba, receiving a large estate of land and
Indian slaves for his effort. In
1510, he accompanied
Diego Velázquez de Cuéllar, an aide of the governor of Hispaniola, in his expedition to conquer Cuba. In
1518 Velázquez put him in command of an expedition to explore and secure the interior of
Mexico for colonization.
In
1517,
Francisco Hernández de Córdoba discovered the
Yucatán Peninsula. This was the first
European encounter with an advanced civilization in the
Americas, with solidly-built buildings and a complex social organization which they recognized as being comparable to those of the
Old World; they also had reason to expect that this new land would have
gold. All of this encouraged two further expeditions, the first in
1518 under the command of
Juan de Grijalva, and the second in 1519 under the command of
Hernán Cortés, which led to the
Spanish exploration, military invasion, and ultimately settlement and colonization known as the
Conquest of Mexico. Hernández did not live to see the continuation of his work: he died in
1517, the year of his expedition, as the result of the injuries and the extreme thirst suffered during the voyage, and disappointed in the knowledge that
Diego Velázquez had given precedence to Grijalva as the captain of the next expedition to Yucatán.
In
1523,
Ãngel de Villafañe sailed to
Mexico City and shipwrecked along the coast of
Padre Island,
Texas in
1554. When word of the disaster reached Mexico City, the viceroy requested a rescue fleet and immediately sent Villafañe marching overland to find the treasure-laden vessels. Villafañe traveled to Pánuco and hired a ship to transport him to the site, which had already been visited from that community. He arrived in time to greet GarcÃa de Escalante Alvarado (a nephew of Pedro de Alvarado), commander of the salvage operation, when Alvarado arrived by sea on
July 22,
1554. The team labored until September 12 to salvage the Padre Island treasure. This loss, in combination with other ship disasters around the Gulf of Mexico, gave rise to a plan for establishing a settlement on the northern Gulf Coast to protect shipping and more quickly rescue castaways. As a result, the expedition of
Tristán de Luna y Arellano was sent and landed at Pensacola Bay on
August 15,
1559.
On
December 11,
1526,
Charles V granted
Pánfilo de Narváez a license to claim what is now the
Gulf Coast of the United States, known as the
Narváez expedition. The contract gave him one year to gather an army, leave
Spain, be large enough to found at least two towns of one hundred people each, and garrison two more fortresses anywhere along the coast. On
April 7,
1528, they spotted land north of what is now
Tampa Bay. They turned south and traveled for two days looking for a great harbor the master pilot Miruelo knew of. Sometime during these two days, one of the five remaining ships was lost on the rugged coast, but nothing else is known of it.
In
1697,
Pierre Le Moyne d'Iberville sailed for
France and was chosen by the Minister of Marine to lead an expedition to rediscover the mouth of the
Mississippi River and to colonize
Louisiana which the
English coveted. Iberville's fleet sailed from Brest on
24 October 1698. On
January 25,
1699, Iberville reached Santa Rosa Island in front of
Pensacola founded by the
Spanish; he sailed from there to
Mobile Bay and explored Massacre Island, later renamed
Dauphin Island. He cast anchor between
Cat Island and
Ship Island; and on
February 13,
1699, he went to the mainland,
Biloxi, with his brother
Jean-Baptiste Le Moyne de Bienville. On
May 1,
1699, he completed a fort on the north-east side of the
Bay of Biloxi, a little to the rear of what is now
Ocean Springs, Mississippi. This fort was known as
Fort Maurepas or Old Biloxi. A few days later, on
May 4, Pierre Le Moyne sailed for France leaving his teenage brother, Jean-Baptiste Le Moyne, as second in command to the French commandant.
Principal features
Gulf beach near Sabine Pass.
The Gulf of Mexico's eastern, north, and northwestern shores lie along the US states of
Florida,
Alabama,
Mississippi,
Louisiana, and
Texas. This coastline spans 1,630 miles, receiving water from thirty-three major rivers that drain 31 states.
[4] The Gulf's southwestern and southern shores lie along the
Mexican states of
Tamaulipas,
Veracruz,
Tabasco,
Campeche,
Yucatán, and the northernmost tip of
Quintana Roo. On the southeast it is bordered by
Cuba. It supports major American, Mexican and Cuban fishing industries. The outer margins of the wide continental shelves of Yucatán and Florida receive cooler,
nutrient-enriched waters from the deep by a process known as
upwelling, which stimulates plankton growth in the
euphotic zone. This attracts fish, shrimp, and squid.
[5] River drainage and atmospheric fallout from industrial coastal cities also provide nutrients to the coastal zone.
The
Gulf Stream, a warm Atlantic Ocean current and one of the strongest
ocean currents known, originates in the gulf, as a continuation of the
Caribbean Current-Yucatán Current-
Loop Current system. Other circulation features include the anticyclonic
gyres which are shed by the
Loop Current and travel westward where they eventually dissipate, and a permanent cyclonic
gyre in the
Bay of Campeche. The
Bay of Campeche in Mexico constitutes a major arm of the Gulf of Mexico. Additionally, the gulf's shoreline is fringed by numerous bays and smaller inlets. A number of rivers empty into the gulf, most notably the
Mississippi River in the northern gulf, and the
Grijalva and
Usumacinta Rivers in the southern gulf. The land that forms the gulf's coast, including many long, narrow barrier islands, is almost uniformly low-lying and is characterized by marshes and swamps as well as stretches of sandy beach.
The
continental shelf is quite wide at most points along the coast, most notably at the Florida and
Yucatán Peninsulas. The shelf is exploited for its
oil by means of offshore drilling rigs, most of which are situated in the western gulf and in the
Bay of Campeche. Another important commercial activity is fishing; major catches include red snapper, amberjack, tilefish, swordfish, and various grouper, as well as shrimp and crabs. Oysters are also harvested on a large scale from many of the bays and sounds. Other important industries along the coast include shipping, petrochemical processing and storage, military use, paper manufacture, and tourism.
Graph showing the overall water temperature of the Gulf between Hurricanes
Katrina and
Rita. Although Katrina cooled waters in its path by up to 4°C, they had rebounded by the time of Rita's appearance.
The gulf's warm water temperature can feed powerful Atlantic
hurricanes causing extensive human death and other destruction as happened with
Hurricane Katrina in 2005. In the Atlantic, a hurricane will draw up cool water from the depths and making it less likely that further hurricanes will follow in its wake (warm water being one of the preconditions necessary for their formation). However, the Gulf is shallower and its entire water column is warm. When a hurricane passes over, although the water temperature may drop it soon rebounds and becomes capable of supporting another tropical storm.
[6]
The Gulf is considered
aseismic: however, mild tremors have been recorded throughout history (usually 5.0 or less on the
Richter scale). A 6.0 tremor was recorded on
September 10,
2006, 250 miles off the coast of
Florida which caused no damage, but could be felt throughout the
Southeastern United States. No damage or injuries were reported.
[7]
Earthquakes such as this may be caused by interactions between sediment loading on the sea floor and adjustment by the crust.
[8]
Pollution
Because of the ever increasing amount of
nitrogen and
phosphates dissolved in the waters of the Gulf of Mexico, pollution has more than doubled since
1950. Current estimates suggest that three times as much nitrogen is being carried into the Gulf today compared with levels 30 years ago or at any time in history in the water. Every summer there is now an area south of the Louisiana coastline, larger than the
U.S. state of
Massachusetts at over 7,000 mi² (18,000 km²) that is
hypoxic. These waters do not carry enough
oxygen to sustain marine life. This annually enlarging
dead zone is a major threat to the fishing industry and to public health.
Fishing boats in Biloxi
Also, there are frequent "
red tide" algae blooms
[9] that kill fish and marine mammals and cause respiratory problems in humans and some domestic animals when the blooms reach close to shore. This has especially been plaguing the southwest Florida coast, from the
Florida Keys to north of
Pasco County, Florida.
See also
★
Charlotte Harbor Estuary, Florida
★
Brine pool
★
Gulf Coast
References
1. General Facts about the Gulf of Mexico
2. Dinosaur Extinction Page
3. gulfbase.org
4. National Water Program Guidance: FY 2005
5. GULF OF MEXICO
6. Warm Waters Provide Fuel for Potential Storms
7. Central Florida Feels Quake
8. Earthquakes in the Gulf of Mexico
9. The Gulf of Mexico Dead Zone and Red Tides
External links
★
6.0 Earthquake reported on 9-10-2006
★
GSA article on Gulf seismic activity from 1982
★
EPA factsheet on hypoxia
★
Gulf of Mexico hypoxia
★
Gulf of Mexico Integrated Science
Gallery
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