|
|
|
The Gulf of Mexico
|
|
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 of 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.
| |
|
|
|
|
Effect of the Gulf Current on Earth's Climate and effects of Global Warming |
The Gulf Current flows from Florida to Cape Hatteras, before turning around at Cape Hatteras and flowing into the Atlantic and eastwards, to Europe. The warm current together with the colder Atlantic water off Cape Hatteras combine to form a highly sensitive water body having a significant impact on the daily weather, seasons and climatic conditions in the Northern Hemisphere. According to a study published in the December 2005 issue of Nature, the speed of the Gulf Stream current (the one that keeps Europe warm despite the fact that the UK is as far north as Hudson Bay) has slowed by about 30% since 1957. Actually, the study notes that the slowing has mostly happened in the years since 1998. Dr. Bill Curry from the Woods Hole Oceanographic Institute presented solid evidence in a talk at Michigan State University that the gulf-stream had shut off entirely for periods of thousands of years at least twice in the last 20,000 years (during events known as the Younger Dryas (12,000 years ago) and the Heinrich Events (a variety of them). During such events, armadas of icebergs broke off from glaciers and traversed the North Atlantic. The icebergs contained rock mass eroded by the glaciers, and as they melted, this matter was dropped onto the sea floor as "ice rafted debris". The icebergs' melting caused prodigious amounts of fresh water to be added to the North Atlantic. Such inputs of cold, fresh water may well have altered the density-driven thermohaline circulation patterns of the ocean, and often coincide with indications of global climate fluctuations. Heinrich events are global climate fluctuations which coincide with the destruction of northern hemisphere ice shelves, and the consequent release of a prodigious volume of sea ice and icebergs. Heinrich events are observed during the last glacial period; the low resolution of the sedimentary record before this point makes it impossible to deduce whether they occurred during other glacial periods in the Earth's history.
Alley & MacAyeal (1994) estimate the volume of fresh water added to the North Atlantic over each 500 year event at around 3.7±1.2×10¹¹ km³ — which would weigh four hundred million trillion tonnes. It is barely surprising that effects of such a huge influx of cold, fresh water into the oceans were of global extent. Whilst several geological indicators fluctuate approximately in time with these Heinrich events, difficulties in precise dating and correlation make it difficult to tell whether the indicators precede or lag Heinrich events, or in some cases whether they are related at all. Heinrich events are often marked by many changes on the earth, including the following:
Decreased Oxygen-18 (a natural, stable isotope of oxygen) of the northern (Nordic) seas and East Asian stalactites (speleothems), which by proxy suggests falling global temperature (or rising ice volume) (Bar-Matthews et al. 1997)
Decreased oceanic salinity, due to the influx of fresh water
Increased terrigenous runoff from the continents, measured near the mouth of the Amazon River
Increased grain size in wind-blown loess in China, suggesting stronger winds (Porter & Zhisheng 1995)
Changes in relative Thorium-230 abundance, reflecting variations in ocean current velocity
Increased deposition rates in the northern Atlantic, reflected by an increase in continentally derived sediments (lithics) relative to background sedimentation (Heinrich 1988)
Pollen indications of cold-loving pines replacing oaks on the North American mainland (Grimm et al. 1993)
The global extent of these records illustrates the dramatic impact of Heinrich events.
|
|
Geologic History of the Gulf of Mexico |
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. There is evidence that the Chicxulub Crater was formed when a large meteorite hit the earth 65 million years ago which may have impacted the extinction of the dinosaurs. The Chicxulub Crater (cheek-shoo-LOOB) is an ancient impact crater buried underneath the Yucatán Peninsula, with its center located approximately underneath the town of Chicxulub, Yucatán, Mexico.
|
|
Effect of the Gulf of Mexico Meteor impact on Earth's evolution
|
The meteorite's estimated size was about 10 km (6 mi) in diameter, releasing an estimated 500 zettajoules (5.0×1023 joules) of energy, approximately 100 teratons of TNT (1014 tons),[1] on impact. By contrast, the most powerful man-made explosive device ever detonated, the Tsar Bomba or Emperor Bomb, had a yield of only 50 megatons, which would make this impact 2,000,000 times more powerful. The impact would have caused some of the largest megatsunamis in Earth's history. These would have spread in all directions, hitting the Caribbean island of Cuba especially hard. A cloud of dust, ash and steam would spread itself from the crater. The pieces of the meteorite would have rained all over Earth, igniting global wildfires. The shock waves would have continued hundreds of kilometers into the planet, causing global earthquakes and volcanic eruptions. The emission of dust and particles covered the entire surface of the earth for several years, possibly a decade, creating a harsh environment that many leading geologists and paleontologists now believe led to the extinction of the non-avian dinosaurs, many plants, and other lifeforms that depend on photosynthesis to survive.
|
|
|
|
|
|
|
|
|