New Evidence Supports Theory of Cosmic Impact and Extinction

 

An international team of researchers has discovered new evidence that a cosmic impact may have coincided with the extinction of mammoths and giant ground sloths.

The 18-member team, which includes Northern Arizona University (NAU) geologist Ted Bunch, and James Wittke, NAU geologic materials analyst, recently had its findings published in the Proceedings of the National Academy of Sciences (doi: 10.1073/pnas.1204453109) in June 2012. The study is available here.

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Mammoth wipe out

The researchers found melt-glass material in a thin layer of sedimentary rock in Pennsylvania, South Carolina, and Syria. According to the study, the material, which dates back nearly 13,000 years, was formed at temperatures of 1,700 Celsius to greater than 2,200 degrees Celsius and is the result of a cosmic body impacting Earth’s atmosphere.

These new data are the latest to support the hypothesis that proposes a cosmic impact occurred 12,900 years ago at the onset of an unusual cold climatic period called the Younger Dryas. This episode occurred at or close to the time of extinction of the North American megafauna, including mammoths and giant ground sloths, and the disappearance of the prehistoric and widely distributed Clovis culture.

Morphological and geochemical evidence of the melt-glass confirms that the material is not volcanic or of human-made origin, Bunch said. "We’ve seen melt-glass in similar impact events such as Meteor Crater in Arizona. The temperatures required to produce such melt-glass materials may be equal to an atomic bomb aerial burst.”

The material evidence supporting the Younger Dryas boundary cosmic impact hypothesis spans three continents, and covers nearly one-third of the planet--from California to western Europe and into the Middle East. The discovery extends the range of evidence into Syria, the easternmost site yet identified in the northern hemisphereOther researchers have found similar deposits in South America and Mexico. The researchers have yet to identify a limit to the debris field of the impact.

Bunch said the three sites in North America and the Middle East, separated by 1,000 to 10,000 kilometers, likely represent three or more major impact epicenters related to the Younger Dryas event and could be attributed to multiple objects or fragments of an asteroid or comet.

 --Adapted from “Inside NAU”