Dinosaurs: Their Lives, Their Deaths and Their Evolution!

by Dr. Bob Gardner
Department of Mathematics
Department of Physics and Astronomy
Institute of Mathematical and Physical Sciences
East Tennessee State University

The End of the Dinosaurs!

A number of theories have been proposed to explain the extinction of the dinosaurs. These have included theories involving volcanism, the spread of disease through migration, and the idea that dinosaurs were poorly designed and that they simply weren't able to adapt to a changing world (the latter idea seems unlikely given their 150 million plus years of success).

Today, the leading theory is that dinosaurs were wiped out when an asteroid 6 miles wide collided with the Earth 65 million years ago.

In 1979 Luis and Walter Alvarez studied the layer of sediment which was deposited between the Cretaceous and Tertiary Periods. They found extremely high concentrations of the element iridium. This element is several thousand times more abundant in meteoric dust than it is on the surface of the Earth.
This lead the Alvarez's to conclude that there was a collision of an asteroid approximately 6 miles wide with the Earth at the end of the Cretaceous. However, in 1979 there was no evidence of the impact site in the form of a crater.
One possible reason for this is that two-thirds of the Earth's surface is covered with water where an impact would not leave a visible crater. In the mid 1980's, a large underground circular structure was discovered under the Yucatan Peninsula.
Near the town of Chicxulub, the structure is over 100 miles in diameter and radioactive dating reveals an age of 65 million years. Other evidence that this was an asteroid impact includes the presence of shocked quartz near the impact area and an abundance of glass particles called tektites throughout the Caribbean.
Upon impact, the asteroid would have vaporized rock and the atmosphere would fill with dust and water vapor. Many paleontologists think that these are the conditions that killed off the dinosaurs.

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