Featured Research

from universities, journals, and other organizations

'Snowball Earth' hypothesis challenged

Date:
October 12, 2011
Source:
CNRS (Délégation Paris Michel-Ange)
Summary:
The hypothesis that Earth was completely covered in ice 635 million years ago has received a serious blow. The atmospheric concentration of carbon dioxide during that period was much lower than previously thought, according to a team of researchers.

Outcrop in the Terconi quarry, Mato Grosso, Brazil. The lower part shows a pink dolomite layer overlain by grey limestone, richer in organic matter. These carbonates lie directly above Marinoan glacial sediments.
Credit: © Pierre Sansjofre

The hypothesis that Earth was completely covered in ice 635 million years ago has received a serious blow. The atmospheric concentration of carbon dioxide during that period was much lower than previously thought, according to a team of French researchers from the Institut de Physique du Globe de Paris (CNRS/IPGP/Université Paris Diderot), working in collaboration with scientists from Brazil and the U.S.

Their work, published in the journal Nature, challenges part of the so-called 'Snowball Earth' hypothesis and rekindles the debate about the origins of the deglaciation mechanism.

Earth has experienced several extreme glacial events, two of which took place during the aptly named Cryogenian period (710-630 million years ago). In 1992 and 1998 scientists hypothesized that around 635 million years ago our planet underwent a major glacial episode that left it entirely smothered in ice. Today still, the question of how this episode came to an end remains unanswered, given that ice reflects more solar radiation back into space than rocks do. In the Snowball Earth hypothesis, it is assumed that enough CO2 of volcanic origin had built up in the atmosphere for this greenhouse gas to warm up the surface of the planet and cause the ice to melt. According to this scenario, CO2 concentrations must have fluctuated around 120,000 ppmv (parts per million by volume) -- i.e.,12%, which is 300 times greater than CO2 concentrations today.

In order to assess the atmospheric concentration of CO2 at that time, the French, Brazilian and US researchers studied carbonates deposited 635 million years ago (the Marinoan glaciation). These sediments cap the glacial deposits of that period, believed to have witnessed a global glaciation known as Snowball Earth. The study is based on the difference in carbon isotopic composition between carbonates and organic matter in fossilized organisms, which reflects atmospheric concentrations of CO2. The results show that CO2 concentrations were very close to what they are today (less than 3,200 ppmv), which is far from being sufficient to bring about the end of a glacial episode of this magnitude.

This work not only challenges part of the Snowball Earth hypothesis, but also implies that these glacial episodes were not as intense as previously suggested. Moreover, this data is consistent with the idea that the atmosphere at the same period was much more oxygen-poor, around 1%, as compared to today's levels of approximately 20%. Scientists will therefore need to examine alternative deglaciation mechanisms or gases other than CO2, such as methane, which has also been suggested as part of this hypothesis.


Story Source:

The above story is based on materials provided by CNRS (Délégation Paris Michel-Ange). Note: Materials may be edited for content and length.


Journal Reference:

  1. P. Sansjofre, M. Ader, R. I. F. Trindade, M. Elie, J. Lyons, P. Cartigny, A. C. R. Nogueira. A carbon isotope challenge to the snowball Earth. Nature, 2011; 478 (7367): 93 DOI: 10.1038/nature10499

Cite This Page:

CNRS (Délégation Paris Michel-Ange). "'Snowball Earth' hypothesis challenged." ScienceDaily. ScienceDaily, 12 October 2011. <www.sciencedaily.com/releases/2011/10/111012083450.htm>.
CNRS (Délégation Paris Michel-Ange). (2011, October 12). 'Snowball Earth' hypothesis challenged. ScienceDaily. Retrieved August 23, 2014 from www.sciencedaily.com/releases/2011/10/111012083450.htm
CNRS (Délégation Paris Michel-Ange). "'Snowball Earth' hypothesis challenged." ScienceDaily. www.sciencedaily.com/releases/2011/10/111012083450.htm (accessed August 23, 2014).

Share This




More Earth & Climate News

Saturday, August 23, 2014

Featured Research

from universities, journals, and other organizations


Featured Videos

from AP, Reuters, AFP, and other news services

Airlines on Iceland Volcano Alert

Airlines on Iceland Volcano Alert

Reuters - Business Video Online (Aug. 22, 2014) — Iceland evacuates an area north of the country's Bardarbunga volcano, as the country's civil protection agency says it cannot rule out an eruption. Authorities have already warned airlines. As Joel Flynn reports, ash from the eruption of the Eyjafjallajokull volcano in 2010 shut down much of Europe's airspace for six days. Video provided by Reuters
Powered by NewsLook.com
Endangered Red Wolves Face Uncertain Future

Endangered Red Wolves Face Uncertain Future

AP (Aug. 22, 2014) — A federal judge temporarily banned coyote hunting to save endangered red wolves, but local hunters say that the wolf preservation program does more harm than good. Meanwhile federal officials are reviewing its wolf program in North Carolina. (Aug. 22) Video provided by AP
Powered by NewsLook.com
Coal Gas Boom in China Holds Climate Risks

Coal Gas Boom in China Holds Climate Risks

AP (Aug. 22, 2014) — China's energy revolution could do more harm than good for the environment, despite the country's commitment to reducing pollution and curbing its carbon emissions. (Aug. 22) Video provided by AP
Powered by NewsLook.com
Microbrewery Chooses Special Can for Its Beer

Microbrewery Chooses Special Can for Its Beer

AP (Aug. 22, 2014) — Aluminum giant, Novelis, has partnered with Red Hare Brewing Company to introduce the first certified high-content recycled beverage can. (Aug. 22) Video provided by AP
Powered by NewsLook.com

Search ScienceDaily

Number of stories in archives: 140,361

Find with keyword(s):
 
Enter a keyword or phrase to search ScienceDaily for related topics and research stories.

Save/Print:
Share:  

Breaking News:
from the past week

In Other News

... from NewsDaily.com

Science News

Health News

Environment News

Technology News



Save/Print:
Share:  

Free Subscriptions


Get the latest science news with ScienceDaily's free email newsletters, updated daily and weekly. Or view hourly updated newsfeeds in your RSS reader:

Get Social & Mobile


Keep up to date with the latest news from ScienceDaily via social networks and mobile apps:

Have Feedback?


Tell us what you think of ScienceDaily -- we welcome both positive and negative comments. Have any problems using the site? Questions?
Mobile iPhone Android Web
Follow Facebook Twitter Google+
Subscribe RSS Feeds Email Newsletters
Latest Headlines Health & Medicine Mind & Brain Space & Time Matter & Energy Computers & Math Plants & Animals Earth & Climate Fossils & Ruins