Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Why is the Earth’s mantle conductive?

04.12.2008
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. 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 kms, 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 (1). 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 (2) and emitted into the atmosphere in gaseous form, as CO2.

Based on lab measurements at CNRS’s CEMHTI (3), 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 (4) 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.

Julien Guillaume | alfa
Further information:
http://www.cnrs.fr

More articles from Earth Sciences:

nachricht Predicting unpredictability: Information theory offers new way to read ice cores
07.12.2016 | Santa Fe Institute

nachricht Sea ice hit record lows in November
07.12.2016 | University of Colorado at Boulder

All articles from Earth Sciences >>>

The most recent press releases about innovation >>>

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

Im Focus: Significantly more productivity in USP lasers

In recent years, lasers with ultrashort pulses (USP) down to the femtosecond range have become established on an industrial scale. They could advance some applications with the much-lauded “cold ablation” – if that meant they would then achieve more throughput. A new generation of process engineering that will address this issue in particular will be discussed at the “4th UKP Workshop – Ultrafast Laser Technology” in April 2017.

Even back in the 1990s, scientists were comparing materials processing with nanosecond, picosecond and femtosesecond pulses. The result was surprising:...

Im Focus: Shape matters when light meets atom

Mapping the interaction of a single atom with a single photon may inform design of quantum devices

Have you ever wondered how you see the world? Vision is about photons of light, which are packets of energy, interacting with the atoms or molecules in what...

Im Focus: Novel silicon etching technique crafts 3-D gradient refractive index micro-optics

A multi-institutional research collaboration has created a novel approach for fabricating three-dimensional micro-optics through the shape-defined formation of porous silicon (PSi), with broad impacts in integrated optoelectronics, imaging, and photovoltaics.

Working with colleagues at Stanford and The Dow Chemical Company, researchers at the University of Illinois at Urbana-Champaign fabricated 3-D birefringent...

Im Focus: Quantum Particles Form Droplets

In experiments with magnetic atoms conducted at extremely low temperatures, scientists have demonstrated a unique phase of matter: The atoms form a new type of quantum liquid or quantum droplet state. These so called quantum droplets may preserve their form in absence of external confinement because of quantum effects. The joint team of experimental physicists from Innsbruck and theoretical physicists from Hannover report on their findings in the journal Physical Review X.

“Our Quantum droplets are in the gas phase but they still drop like a rock,” explains experimental physicist Francesca Ferlaino when talking about the...

Im Focus: MADMAX: Max Planck Institute for Physics takes up axion research

The Max Planck Institute for Physics (MPP) is opening up a new research field. A workshop from November 21 - 22, 2016 will mark the start of activities for an innovative axion experiment. Axions are still only purely hypothetical particles. Their detection could solve two fundamental problems in particle physics: What dark matter consists of and why it has not yet been possible to directly observe a CP violation for the strong interaction.

The “MADMAX” project is the MPP’s commitment to axion research. Axions are so far only a theoretical prediction and are difficult to detect: on the one hand,...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

ICTM Conference 2017: Production technology for turbomachine manufacturing of the future

16.11.2016 | Event News

Innovation Day Laser Technology – Laser Additive Manufacturing

01.11.2016 | Event News

#IC2S2: When Social Science meets Computer Science - GESIS will host the IC2S2 conference 2017

14.10.2016 | Event News

 
Latest News

NTU scientists build new ultrasound device using 3-D printing technology

07.12.2016 | Health and Medicine

The balancing act: An enzyme that links endocytosis to membrane recycling

07.12.2016 | Life Sciences

How to turn white fat brown

07.12.2016 | Health and Medicine

VideoLinks
B2B-VideoLinks
More VideoLinks >>>