Evidence of Asteroid Impact as Cause of Cretaceous Extinction

We have all heard of the asteroid impact that caused the extinction of the dinosaurs 65 million years at the Cretaceous-Tertiary boundary, but probably very few people know the evidence to support this.

Image courtesy of Wikipedia.org

Here are the facts:
- In 1980 a research team led by physicist Luis Alvarez, his son geologist Walter Alvarez and chemists Frank Asaro and Helen Michels discovered that sedimentary rock layers found all over the world at the Cretaceous–Paleogene (formerly Tertiary) boundary contained high concentrations of iridium.
-iridium is a metal that is common in asteroids and meteorites, but is extremely rare in the Earth's crust.
-samples of clay with this high iridium are similar all over the world in the same Cretaceous-Tertiary boundary rock

Image compliments of www.scielo.org.mx


-Such widespread, world-wide physical evidence is most convincing, that in fact, the Cretaceous-Tertiary extinction was likely caused by the impact of an asteroid approximately 10 km in diameter.
-some years later, a large impact crater was discovered beneath the Yucatan Peninsula in Mexico, however it was largely covered by the limestone rock of the peninsula that was deposited over top of the crater and then hardened in the last 65 million years. This is thought to be the crater from the asteroid.

The image above is a gravity anomaly map of the north side of the Yucatan Peninsula. You can see a clear concentric object in the image. The while line is the current coastline of the north Yucatan. Small white holes dotting the outer concentric edge on land are sink holes through the limestone rock that formed over the crater in the last 65 million years.

Images above are courtesy of Wikipedia.org
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-the age of the asteroid impact (based on the radioactive decay of argon for rock in the crater) was reported by Paul Renne of the Berkeley Geochronology Center. He indicated that the asteroid impact was 66,038,000 years ago, + or - 11,000 years.

The release of energy of such a catastrophic event would have been equivalent to about 1 x 108 megatons or 2 Million times greater than the largest nuclear bomb ever tested.  While this asteroid impact caused the extinction 75% of all life on Earth, this allowed small mammals to thrive, giving rise eventually to all human life!

Had it not been for this asteroid impact, it is quite possible that mammals and humans would not have become the dominant species on Earth!

Maddalena Environmental Inc.
Al Maddalena