The originality of this work, carried out by the scientists of the Institut de mineralogie et de physique des milieux condenses (UPMC/ Universite Paris Diderot/ Institut de Physique du Globe/CNRS/IRD), lies in the use of X-ray diffraction at the European Synchrotron Radiation Facility in Grenoble (France). The results will have an effect in the understanding of the dynamics, composition and the formation of the depths of our planet.

On top of the core of the Earth, constituted of liquid iron, lies the solid mantle, which is made up essentially of magnesium oxides, iron and silicon. The border between the core and the mantle, located at 2900 km under our feet, is highly intriguing to geophysicists.

With a pressure of around 1.4 million times the atmospheric pressure and a temperature of more than 4000 Kelvin, this zone is the home to chemical reactions and changes in states of matter still unknown. The seismologists who have studied this subject have acknowledged an abrupt reduction of the speed of the seismic waves, which sometimes reach 30% when getting close to this border.

This fact has led scientists to formulate the hypothesis, for the last 15 years, of the partial melting of the Earth mantle at the level of this mantle-core border. Now it has been confirmed.

In order to access the depths of the Earth, scientists have not only seismological images but also a precious experimental technique: diamond anvil cells, coupled with a heating layer. This instrument allows to re-create the same pressure and temperature condition than those in the interior of the Earth, on samples of a few microns.

This is the technique used by the researchers of the Institut de mineralogie et de physique des milieux condenses on natural samples that are representatives of the Earth mantle and that have been put under pressures of more than 140 gigapascals (or 1.4 million times the atmospheric pressure), and temperatures of more than 5000 Kelvin.

A new approach to this study has been the use of the X-ray diffraction technique at the European synchrotron ESRF. This has allowed the scientists to determine what mineral phases melt first, and they have also established, without extrapolation, fusion curves of the deep Earth mantle, i.e. the characterization of the passage from a solid state to a partially liquid state. Their observations show that the partial fusion of the mantle is possible when the temperature approaches 4200 Kelvin.

These experiments also prove that the liquid produced during this partial fusion is dense and that it can hold multiple chemical elements, among which are important markers of the dynamics of the Earth mantle.

These studies will allow geophysicists and geochemists to achieve a deeper knowledge of the mechanisms of differentiation of the Earth and the history of its formation, which started around 4.5 billion years ago.

Share This Article With Planet Earth

del.icio.us	Digg	Reddit
YahooMyWeb	Google	Facebook

Related Links
European Synchrotron Radiation Facility
Dirt, rocks and all the stuff we stand on firmly

Unrealistic to expect immediate quake recovery in Haiti: US Millennium Development Goals seek end to poverty, hunger Chile celebrates bicentennial with miners' fate in focus UN gathers pledges for two billion dollar Pakistan appeal Physicists Control Chemical Reactions Mechanically Oracle reaches for the business computing "cloud" Samsung takes aim at Apple's iPad, iTunes Rogue satellite still 'talking' Documentary shows dramatic shrinking of the Aral Sea 'Noise' is symptom of coral reef health Global Fisheries Research Finds Promise And Peril Drought shrinks Amazon River to lowest level in 47 years Russia, Canada trade rival Arctic claims Glaciers Help High-Latitude Mountains Grow Taller Arctic sea ice shrinks to third lowest area on record Arctic ice melting quickly, report says China's SAIC considering stake in GM: report Sub-zero seed freezes aim to save orchids from extinction Global Project Underway To Preserve Yam Biodiversity NGOs call for African biodiversity centre NASA's Armada Of Research Aircraft Monitor Hurricane Karl Tsunami Detection Improves But Coastal Areas Still Vulnerable Seven dead, 20 missing as landslide buries road in Mexico Food threat looms for Pakistan child flood victims: UN French troops sent to Niamey after kidnappings: sources Mauritanian troops battle Al-Qaeda-linked fighters in Mali Kenya may be lifeline for new Sudan state Termites Foretell Climate Change In Africa's Savannas A Chip Off the Early Hominin Tooth Factfile on world population growth Roma issue could overshadow EU summit Scientists Glimpse Dance Of Skeletons Inside Neurons