International Consensus — Link Between Asteroid Impact and Mass Extinction Is Rock Solid
March 4, 2010
Reporting in the journal Science, a team of over three dozen international scientists examined the geology of the Chicxulub impact crater and the transition that occurred at the K-T boundary mass extinction horizon and conclude that the link between the two is solid: The Chicxulub impact event caused the mass extinction of dinosaurs and the majority of life on Earth 65 million years ago.
Dr. David A. Kring, a geologist and Senior Staff Scientist at the Lunar and Planetary Institute (LPI) in Houston, joins the team in this international consensus. Nearly 20 years ago, Kring (then at the University of Arizona) announced the discovery of shocked quartz and other evidence of impact from a 1.6-kilometer-deep (1 mile) drill hole into a buried crater on the Yucatán Peninsula of Mexico. His team named the crater Chicxulub for a Mayan village above the center of the crater. Chicxulub means “tail of the devil,” which Kring thought a perfect name for a dinosaur-killing impact event.
That 1991 announcement, with co-authors William Boynton and Alan Hildebrand, was made at the LPI’s Lunar and Planetary Science Conference at NASA’s Johnson Space Center (Lunar and Planetary Science XXII, pp. 755–756). The consensus report in the March 5 issue of Science is being published coincident with this year’s Lunar and Planetary Science Conference.
The Science research team involves a distinguished panel of 41 experts from Europe, the U.S., Mexico, Canada, and Japan. The international team synthesized stratigraphic, paleontological, petrological, and geochemical data associated with the crater and distributed in K-T boundary sections around the world. They conclude there is a unique layer of debris ejected from a crater that is compositionally linked to Chicxulub and coincident with the horizon in the rock record where life was extinguished. They further rule out significant effects of volcanism. Thus, Chicxulub is responsible for the demise of dinosaurs and most living organisms on land and in the seas at that time.
“Combining all available data from different science disciplines led us to conclude that a large asteroid impact 65 million years ago in modern-day Mexico was the major cause of the mass extinctions,” says Dr. Peter Schulte, Assistant Professor at the University of Erlangen in Germany and lead author of the paper.
Kring adds, “I am elated with the community’s consensus about the link between the Chicxulub Crater and the K-T boundary mass extinction. The data are compelling.” Moreover, he says dozens of international investigators have worked tirelessly to discern the detailed elements of this fascinating chapter in Earth history. That work, also updated in the new paper, outlines the environmental effects of the impact event: darkness, impact heating, deforestation, acid rain, and greenhouse warming. Many of the environmental effects caused by the Chicxulub impact event are similar to those that are beginning to plague today’s world. By measuring the consequences of those effects 65 million years ago, scientists will be better able predict the effects of those environmental assaults today.
The Chicxulub impact crater is ~180 kilometers in diameter (112 miles), surrounded by a circular fault ~240 kilometers in diameter (149 miles), and was produced when enough rock (>25 trillion metric tons) was excavated to blanket the entire Earth. The explosive energy of the impact event was equal to ~100 trillion tons of TNT, which is over a billion times more explosive than the bombs that destroyed Hiroshima and Nagasaki and a million times larger than the most explosive nuclear bomb ever tested. The Chicxulub Crater was produced by an asteroid or comet 10 to 15 kilometers in diameter (6 to 7.5 miles), which is so large that its trailing edge was still at the altitude of a cruising airliner when its leading edge hit Earth’s surface. The vast energy of the impact was created by the impactor’s large mass and its cosmic velocity, which was 15–20 kilometers per second (or 34,000 to 45,000 miles per hour) if an asteroid and possibly faster if a comet. That type of impact event occurs on average about once per 100 million years and about five of them occurred during the evolution of complex life on Earth.
The important role of impact cratering in the geologic evolution of Earth was first recognized during the Apollo program, when lunar exploration showed that both Earth and the Moon were constantly the target of space debris. That paved the way for the recognition that impact cratering can affect both the geologic and biologic evolution of a planet.
Last updated March 5, 2010