Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Prehistoric climate change due to cosmic crash in Canada

03.09.2013
Dartmouth-led team reveals cause of global climate shift 12,900 years ago

For the first time, a dramatic global climate shift has been linked to the impact in Quebec of an asteroid or comet, Dartmouth researchers and their colleagues report in a new study.


The high temperatures of the meteorite impact 12,900 years ago produced mm-sized spherules of melted glass with the mullite and corundum crystal structure shown here. Credit: Mukul Sharma

The cataclysmic event wiped out many of the planet's large mammals and may have prompted humans to start gathering and growing some of their food rather than solely hunting big game.

The findings appear next week in the online Early Edition of the Proceedings of the National Academy of Sciences. A preprint of the article is available to journalists starting Wednesday, Aug. 28, at http://www.eurekalert.org/account.php.

The impact occurred about 12,900 years ago, at the beginning of the Younger Dryas period, and marks an abrupt global change to a colder, dryer climate with far-reaching effects on both animals and humans. In North America, the big animals all vanished, including mastodons, camels, giant ground sloths and saber-toothed cats. Their human hunters, known to archaeologists as the Clovis people, set aside their heavy-duty spears and turned to a hunter-gatherer subsistence diet of roots, berries and smaller game.

"The Younger Dryas cooling impacted human history in a profound manner," says Dartmouth Professor Mukul Sharma, a co-author of the study. "Environmental stresses may also have caused Natufians in the Near East to settle down for the first time and pursue agriculture."

It is not disputed that these powerful environmental changes occurred, but there has long been controversy over their cause. The classic view of the Younger Dryas cooling interlude has been that an ice dam in the North American ice sheet ruptured, releasing a massive quantity of freshwater into the Atlantic Ocean. The sudden influx is thought to have shut down the ocean currents that move tropical water northward, resulting in the cold, dry climate of the Younger Dryas.

But Sharma and his co-authors have discovered conclusive evidence linking an extraterrestrial impact with this environmental transformation. The report focuses on spherules, or droplets of solidified molten rock expelled by the impact of a comet or meteor. The spherules in question were recovered from Younger Dryas boundary layers at sites in Pennsylvania and New Jersey, the layers having been deposited at the beginning of the period. The geochemistry and mineralogy profiles of the spherules are identical to rock found in southern Quebec, where Sharma and his colleagues argue the impact took place.

"We have for the first time narrowed down the region where a Younger Dryas impact did take place," says Sharma, "even though we have not yet found its crater." There is a known impact crater in Quebec — the 4-kilometer wide Corossal crater -- but based on the team's mineralogical and geochemical studies, it is not the impact source for the material found in Pennsylvania and New Jersey.

People have written about many impacts in different parts of the world based on the presence of spherules. "It may well have taken multiple concurrent impacts to bring about the extensive environmental changes of the Younger Dryas," says Sharma. "However, to date no impact craters have been found and our research will help track one of them down."

Broadcast studios: Dartmouth has TV and radio studios available for interviews. For more information, visit: http://www.dartmouth.edu/~opa/radio-tv-studios/

John Cramer | EurekAlert!
Further information:
http://www.dartmouth.edu
http://www.dartmouth.edu/~opa/radio-tv-studios/

All articles from Earth Sciences >>>

The most recent press releases about innovation >>>

Die letzten 5 Focus-News des innovations-reports im Überblick:

Im Focus: Researchers Imitate Molecular Crowding in Cells

Enzymes behave differently in a test tube compared with the molecular scrum of a living cell. Chemists from the University of Basel have now been able to simulate these confined natural conditions in artificial vesicles for the first time. As reported in the academic journal Small, the results are offering better insight into the development of nanoreactors and artificial organelles.

Enzymes behave differently in a test tube compared with the molecular scrum of a living cell. Chemists from the University of Basel have now been able to...

Im Focus: Safe glide at total engine failure with ELA-inside

On January 15, 2009, Chesley B. Sullenberger was celebrated world-wide: after the two engines had failed due to bird strike, he and his flight crew succeeded after a glide flight with an Airbus A320 in ditching on the Hudson River. All 155 people on board were saved.

On January 15, 2009, Chesley B. Sullenberger was celebrated world-wide: after the two engines had failed due to bird strike, he and his flight crew succeeded...

Im Focus: Breakthrough with a chain of gold atoms

In the field of nanoscience, an international team of physicists with participants from Konstanz has achieved a breakthrough in understanding heat transport

In the field of nanoscience, an international team of physicists with participants from Konstanz has achieved a breakthrough in understanding heat transport

Im Focus: DNA repair: a new letter in the cell alphabet

Results reveal how discoveries may be hidden in scientific “blind spots”

Cells need to repair damaged DNA in our genes to prevent the development of cancer and other diseases. Our cells therefore activate and send “repair-proteins”...

Im Focus: Dresdner scientists print tomorrow’s world

The Fraunhofer IWS Dresden and Technische Universität Dresden inaugurated their jointly operated Center for Additive Manufacturing Dresden (AMCD) with a festive ceremony on February 7, 2017. Scientists from various disciplines perform research on materials, additive manufacturing processes and innovative technologies, which build up components in a layer by layer process. This technology opens up new horizons for component design and combinations of functions. For example during fabrication, electrical conductors and sensors are already able to be additively manufactured into components. They provide information about stress conditions of a product during operation.

The 3D-printing technology, or additive manufacturing as it is often called, has long made the step out of scientific research laboratories into industrial...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

Booth and panel discussion – The Lindau Nobel Laureate Meetings at the AAAS 2017 Annual Meeting

13.02.2017 | Event News

Complex Loading versus Hidden Reserves

10.02.2017 | Event News

International Conference on Crystal Growth in Freiburg

09.02.2017 | Event News

 
Latest News

A better way to measure the stiffness of cancer cells

01.03.2017 | Health and Medicine

Exploring the mysteries of supercooled water

01.03.2017 | Physics and Astronomy

Research team of the HAW Hamburg reanimated ancestral microbe from the depth of the earth

01.03.2017 | Life Sciences

VideoLinks
B2B-VideoLinks
More VideoLinks >>>