Featured Research

from universities, journals, and other organizations

Why Is The Earth’s Mantle Conductive?

Date:
December 4, 2008
Source:
CNRS (Délégation Paris Michel-Ange)
Summary:
Researchers in France have found that the high conductivity of the Earth's upper mantle is due to molten carbonates. They have demonstrated the very high conductivity of this form of carbon. Their work has revealed the high carbon content of the interior of the upper mantle. This composition can be directly linked to the quantity of carbon dioxide produced by 80% of volcanoes.

Above: Image of the Masai volcano, Oldoinyo Lengia (mountain of the gods) with, in white, a recent flow of liquid carbonate. Below: Two images of the lava lake, illustrating the very fluid character of this lava with extraordinary electrical properties.
Credit: Copyright Hannes Mattsson, ETH Zurich, courtesy CNRS

Researchers from INSU-CNRS, working with chemists at a CNRS research unit, have explained that the high conductivity of the Earth’s upper mantle is due to molten carbonates. They demonstrated the very high conductivity of this form of carbon.

Related Articles


Appearing in the 28 November issue of Science, their work has revealed the high carbon content of the interior of the upper mantle. This composition can be directly linked to the quantity of carbon dioxide produced by 80% of volcanoes. This result is important for quantifying the carbon cycle, which contributes significantly to the greenhouse effect.

Geologists have long claimed that significant amounts of carbon have been present in the Earth’s mantle for thousands of years. Up until now, there was very little direct proof of this hypothesis, and samples from the surface of the mantle contained only very small quantities of carbon. Also, for the last thirty years, scientists have been unable to explain the conductivity of the mantle, which is crossed by natural electrical currents at depths of 70 to 350 km, even though olivine, one of the main mineral components of the upper mantle, is completely isolating.

To explain these phenomena, researchers from the Institut des Sciences de la Terre d'Orléans (ISTO, CNRS / Université de Tours / Université d'Orléans) looked into liquid carbonates, one of the most stable forms of carbon within the mantle, along with graphite and diamond. The Masai volcano is Tanzania is the only place in the world where these carbonates can be observed. Elsewhere, the carbonates are dissolved in basalts and emitted into the atmosphere in gaseous form, as CO2.

Based on lab measurements at CNRS’s CEMHTI, the researchers established the high conductivity of molten carbonates. Their conductivity is 1000 times higher than that of basalt, which was previously thought to be the only potential conductor in the mantle. Fabrice Gaillard and his team have shown that the conductivity of the Earth’s mantle is a result of the presence of small amounts of molten carbonates between chunks of solid rock.

This work shows that the electrical characteristics of the asthenosphere, the conductive part of the upper mantle, are directly connected to the amount of carbonate in the layer. The work also points to varying carbon distribution according to the regions and depth of the mantle. The researchers calculated that the amount of carbon present as liquid carbonate directly within the asthenosphere is between 0.003 and 0.025%, which seems low but makes it possible to explain the amounts of CO2 emitted into the atmosphere by 80% of volcanoes. This nonetheless represents a reservoir of carbon integrated into the mantle which is higher than that present on the surface of the earth. These results are unmatched in helping to quantify the carbon cycle, which plays a major role in the greenhouse effect. Indeed, the CO2 emitted by volcanic activity had never before been evaluated at the source (at the level of the mantle).

The presence of molten carbonates in the asthenosphere certainly has major implications on the viscosity of this region of the mantle, which participates in the sliding of tectonic plates, a phenomenon we know little about. The behavior of liquid carbonates in solids and potential effects on viscosity remain to be studied. Everything seems to indicate that the asthenosphere contains only oxidated forms of carbon (carbonates), and not carbon in its reduced solid form (diamond).

Diamond formation remains mysterious, but researchers are guessing that diamonds form from liquid carbonates at the base of the lithosphere, below the asthenosphere. Enfin, the electrical measurements of the team on liquid carbonates are of interest to the field of clean energy production, as they can be used as electrolytes in high temperature
batteries (eg. lithium carbonate).

This work was funded through a Young Researcher ANR project led by Fabrice Gaillard. He hopes to continue the work on liquid electrolytes through another ANR project and to therefore clarify these new hypotheses.


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. Gaillard et al. Carbonatite Melts and Electrical Conductivity in the Asthenosphere. Science, 2008; 322 (5906): 1363 DOI: 10.1126/science.1164446

Cite This Page:

CNRS (Délégation Paris Michel-Ange). "Why Is The Earth’s Mantle Conductive?." ScienceDaily. ScienceDaily, 4 December 2008. <www.sciencedaily.com/releases/2008/12/081203133823.htm>.
CNRS (Délégation Paris Michel-Ange). (2008, December 4). Why Is The Earth’s Mantle Conductive?. ScienceDaily. Retrieved October 25, 2014 from www.sciencedaily.com/releases/2008/12/081203133823.htm
CNRS (Délégation Paris Michel-Ange). "Why Is The Earth’s Mantle Conductive?." ScienceDaily. www.sciencedaily.com/releases/2008/12/081203133823.htm (accessed October 25, 2014).

Share This



More Matter & Energy News

Saturday, October 25, 2014

Featured Research

from universities, journals, and other organizations


Featured Videos

from AP, Reuters, AFP, and other news services

IKEA Desk Converts From Standing to Sitting With One Button

IKEA Desk Converts From Standing to Sitting With One Button

Buzz60 (Oct. 24, 2014) — IKEA is out with a new convertible desk that can convert from a sitting desk to a standing one with just the push of a button. Jen Markham explains. Video provided by Buzz60
Powered by NewsLook.com
Ebola Protective Suits Being Made in China

Ebola Protective Suits Being Made in China

AFP (Oct. 24, 2014) — A factory in China is busy making Ebola protective suits for healthcare workers and others fighting the spread of the virus. Duration: 00:38 Video provided by AFP
Powered by NewsLook.com
Real-Life Transformer Robot Walks, Then Folds Into a Car

Real-Life Transformer Robot Walks, Then Folds Into a Car

Buzz60 (Oct. 24, 2014) — Brave Robotics and Asratec teamed with original Transformers toy company Tomy to create a functional 5-foot-tall humanoid robot that can march and fold itself into a 3-foot-long sports car. Jen Markham has the story. Video provided by Buzz60
Powered by NewsLook.com
Police Testing New Gunfire Tracking Technology

Police Testing New Gunfire Tracking Technology

AP (Oct. 24, 2014) — A California-based startup has designed new law enforcement technology that aims to automatically alert dispatch when an officer's gun is unholstered and fired. Two law enforcement agencies are currently testing the technology. (Oct. 24) 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:

Strange & Offbeat Stories

 

Space & Time

Matter & Energy

Computers & Math

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