01/05/2012 | Graduate School of Geosciences, Sustainability
Extraterrestrial cause of sudden climate change undermined
Charcoal and diamonds do not confirm an extraterrestrial impact at the end of the last ice age
Dutch researchers claim that nanodiamonds and charcoal found in North America and Europe cannot be considered evidence for an alleged, climate changing, extraterrestrial impact at the end of the last ice age.
Near the end of the last ice age, when temperature was already rising, the world suddenly plunged back into cold conditions. In 2007, American researchers suggested that an extra terrestrial impact over the North American ice sheet was responsible for this rapid climate change. In addition to the rapid cooling, this impact would have caused widespread wildfires with the combined effects leading to the extinction of the spectacular ice age mega fauna,
“However, charcoal and nanodiamonds are also present in younger layers, and thus after the suggested impact. These findings undermine the evidence for an extraterrestrial cause of the climate change.” says Annelies van Hoesel, PhD student at Utrecht University.
The presence of charcoal can easily be explained by natural wildfires. The short cold period from 12,900 to 11,700 years ago, the Younger Dryas period, can also be explained by terrestrial mechanisms. The return to ice age conditions was likely caused by the drainage of a huge melt water lake to the Atlantic Ocean. This input of melt water obstructed the ocean circulation that transports warm waters from the equator to the north. A scenario that has been used in the science-fiction disaster movie ‘The day after tomorrow” in which melting of the icecaps due to global warming leads to a sudden ice age.
With the charcoal and the climate change explained by other mechanisms, the only remaining mystery is the presence of nano- and micro-scale diamonds. More research is needed to see if small diamonds can grow during natural wildfires.
A layer marking the climate change is clearly recognizable in a large part of northwestern and central Europe, and often contains charcoal. This layer, the so-called Usselo layer, has been coupled to the extraterrestrial impact by the original American researchers. For the latest research, the Usselo layer at one site in the Netherlands has been carefully dated and nanodiamonds were discovered using electron microscopy.
The research was carried out by researchers from the Faculty of Geosciences at Utrecht University in collaboration with colleagues from Leiden University and Groningen University. The research will be published this week in the Proceedings of the National Academy of Science.
- Read the article online the PNAS website: Nanodiamonds and wildfire evidence in the Usselo horizon postdate the Allerød-Younger Dryas boundary
- For more information, contact Annelies van Hoesel