Cause of Mass Extinction: The Chicxulub Crater?

A mass extinction occurred approximately sixty-five million years ago and for the longest time it has been a mystery as to how it happened. Many scientists across the globe now believe it was a large projectile that struck near the northwest coast of the Yucatan Peninsula that may have helped lead to the extinction of the dinosaurs. By the early to middle nineties most scientists, now believing that the Chicxulub crater was created at the end of the Cretaceous period, gave the Chicxulub crater the attention it deserved (Frankel, 1999, p. 97).

The actual center of the Chicxulub crater is located at 21.27 degrees north and 89.60 degrees west, near the tiny fishing village of Puerto Chicxulub (Frankel, 1999, p. 104). When the projectile responsible for the crater smashed into the southern Gulf of Mexico, it formed a cavity about 90km across and 30 km deep! (p. 105). The Chicxulub crater may have remained a mystery if scientists had not found it buried under a thousand meters of limestone. It comes in at an astounding 180km (112 miles) in diameter (p. 102)! There are only two other craters that can be compared to the Chicxulub crater: the Sudbury crater in Canada and the Vredefurt crater in South Africa (p. 95). A dozen scientists under the guidance of the one and only Carl Swisher, an expert in argon-argon dating at the Institute of Human Origins in Berkeley, calculated the age of the Chicxulub crater to be about 64. 98 million years (plus or minus 0.05 million years) (Frankel, 1999, p. 96-97). Obviously, this coincides with the time that the dinosaurs disappeared from the face of the Earth.

Now it's time to try to explain the reason for the extinction of so many animal and plant species. After the projectile slammed into the Gulf of Mexico, it's believed that a plume of dust, soot, ash, and a whole bunch of other stuff shot up into the atmosphere. The atmosphere resembled a fireplace as fires burned all around the planet. As the energy returned to the Earth's surface it discharged a radiation output equal to over thirty times the energy the Earth normally receives from the sun. Because of this, the temperature of the soil may have reached as high as 400 degrees Celsius (Frankel, 1999, p. 119). It doesn't take a rocket scientist to realize that most life forms cannot survive such extreme temperatures. The most deadly aftermaths of the impact on dry land were wildfires and balls of fire (an actual Armageddon) (p. 123). Also, when the projectile slammed into the Earth, it probably sent up a rather large amount of toxic metals into the air and these metals were deposited around the globe (p. 127). This means that lakes, streams, and oceans became polluted and many plants and animals died from the toxicity of the metals.

Another hypothesis: the Earth went through a long period of extreme cooling (as much as 15 degrees Celsius) because dust and soot blocked out the sun. However, there is no proof that there was a planet wide temperature drop. Believe it or not, it's believed that the planet experienced a much longer period of warming. How is this known? Well, it turns out that marine fossils (containing limestone) are good temperature indicators because of the oxygen in the limestone (Frankel, 1999, p. 132-134). "The element's two different isotopes, O-16 and O-18, are present in ocean water and incorporated into living shells in a ratio that is closely related to water temperature" (p. 134). The "shift in the oxygen ratio of the fossils" (p. 134) indicated a rise in temperature. Also, the impact probably caused the concentration of carbon dioxide to increase substantially and of course there is an association between increased levels of CO2 and a rise in temperatures (p. 135). Still, dust and soot probably blocked out the sun long enough to kill off a tremendous amount of algae (photosynthetic) and plants, and contributed to the destruction of the primary food chains on land and in the sea which helped to kill of up to 70 % of Earth's living species (p. 131).

Source:

Frankel, C. (1999). The end of the dinosaurs: Chicxulub crater and mass extinctions. Cambridge: Cambridge University Press.