One of the most well known debates in science is over what caused the extinction of the dinosaurs. At the time of the extinction about 65 million years ago, dinosaurs weren't the only creatures to perish: scientists estimate that over 70% of all life on earth came to an end. Explanations for the extinction were for many years provided by two competing theories: One, that the global effects of either increased volcanism or two, the effects of a large object impact created conditions too harsh for most life on earth.
The Chicxulub Crater
In 1978, a geophysicist working for Petroleos Mexicanos (PEMEX, the Mexican state-owned oil company) discovered a huge underwater "arc" with its ends pointing south, in the Caribbean Sea off the Yucatan. When the geophysicist compared this finding with an earlier survey of the Yucatan that had been made in the 1960s he found another arc, but this one was on the Yucatan itself, and its ends pointed north. He matched up the two maps and found that the two arcs joined up in a neat circle, 180 kilometers (112 miles) wide, with its center Puerto Chicxulub(Chicxulub), which is a small coastal village about an hour north of Merida. This underground ‘circle’ was in fact the perimeter of a giant crater that had been formed millions of years earlier.
It wasn’t until the early 1990s that geologists matched rock mineral samples found in North America and throughout the Caribbean to this crater and linked it to the Alvarez Theory of the extinction of the dinosaurs around 65 Million years BC.
The Alvarez Theory postulates that extinction of the dinosaurs was brought on by a large meteorite impacting the earth causing a nuclear winter. This theory has lead to the crater also being called the ‘Alvarez Crater’. |
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In order to cause such a colossal event, the size of the meteor that hit the earth would have had to have been over 10 km (6.2 mi) in diameter and would have released a force close to 100,000 gigatons (100 million megatons, or 100,000,000,000,000 tons) of TNT on impact. That is 6 million times more force than the 1980 Mount St. Helens volcanic eruption and equal to about five million Hiroshima-sized bombs.
How much energy is in TNT? Well… 1 ton of TNT releases 4,200,000,000 Joules of energy and it takes only 1 Joule of energy to lift something the size of an apple 1 meter against the earth’s gravity. |
The impact crater has affected the circulation of groundwater on the Yucatan Peninsula as well. In some areas this groundwater has dissolved the limestone and below ground this has produced caves. On the surface, this has produced cenotes (sinkholes) (pronounced: say-no-tays) which are among the most common features in the limestone topography of the Yucatán Peninsula .Hundreds of cenotes have been found across north-west Yucatan with clusters around the perimeter of the ancient crater. These cenotes later provided water sources in northern Yucatán and were used by the ancient Maya settlements and cities that can be found surrounding them. They also provide water for cities today. An aerial view shows that the cenotes form a ring, like a blue pearl necklace, that is nearly coincident with the rim of the Chicxulub Crater structure, and it is the only visible feature on the surface to indicate a huge crater lurks below.
Andrew Synsyhyn
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