Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Magnetism discovered in the Earth’s mantle

06.06.2019

The huge magnetic field which surrounds the Earth, protecting it from radiation and charged particles from space – and which many animals even use for orientation purposes – is changing constantly, which is why geoscientists keep it constantly under surveillance. The old well-known sources of the Earth’s magnetic field are the Earth’s core and the Earth’s crust: in other words, the ground we stand on. Now researchers show that a form of iron oxide can also retain its magnetic properties in the Earth's mantle. The study has been published in the journal "Nature".

The huge magnetic field which surrounds the Earth, protecting it from radiation and charged particles from space – and which many animals even use for orientation purposes – is changing constantly, which is why geoscientists keep it constantly under surveillance.


The old well-known sources of the Earth’s magnetic field are the Earth’s core – down to 6,000 kilometres deep down inside the Earth – and the Earth’s crust: in other words, the ground we stand on. The Earth’s mantle, on the other hand, stretching from 35 to 2,900 kilometres below the Earth’s surface, has so far largely been regarded as “magnetically dead”.

An international team of researchers from Germany, France, Denmark and the USA has now demonstrated that a form of iron oxide, hematite, can retain its magnetic properties even deep down in the Earth’s mantle. This occurs in relatively cold tectonic plates, called slabs, which are found especially beneath the western Pacific Ocean.

“This new knowledge about the Earth’s mantle and the strongly magnetic region in the western Pacific could throw new light on any observations of the Earth’s magnetic field,” says mineral physicist and first author Dr. Ilya Kupenko from the University of Münster (Germany). The new findings could, for example, be relevant for any future observations of the magnetic anomalies on the Earth and on other planets such as Mars.

This is because Mars has no longer a dynamo and thus no source enabling a strong magnetic field originating from the core to be built up such as that on Earth. It might, therefore, now be worth taking a more detailed look on its mantle. The study has been published in the “Nature” journal.

Background and methods used:

Deep in the metallic core of the Earth, it is liquid iron alloy that triggers electrical flows. In the outermost crust of the Earth, rocks cause magnetic signal. In the deeper regions of the Earth's interior, however, it was believed that the rocks lose their magnetic properties due to the very high temperatures and pressures.

The researchers now took a closer look at the main potential sources for magnetism in the Earth’s mantle: iron oxides, which have a high critical temperature – i.e. the temperature above which material is no longer magnetic. In the Earth’s mantle, iron oxides occur in slabs that are buried from the Earth’s crust further into the mantle, as a result of tectonic shifts, a process called subduction.

They can reach a depth within the Earth’s interior of between 410 and 660 kilometres – the so-called transition zone between the upper and the lower mantle of the Earth. Previously, however, no one had succeeded in measuring the magnetic properties of the iron oxides at the extreme conditions of pressure and temperature found in this region.

Now the scientists combined two methods. Using a so-called diamond anvil cell, they squeezed micrometric-sized samples of iron oxide hematite between two diamonds, and heated them with lasers to reach pressures of up to 90 gigapascal and temperatures of over 1,000 °C (1,300 K). The researchers combined this method with so-called Mössbauer spectroscopy to probe the magnetic state of the samples by means of synchrotron radiation. This part of the study was carried out at the ESRF synchrotron facility in Grenoble, France, and this made it possible to observe the changes of the magnetic order in iron oxide.

The surprising result was that the hematite remained magnetic up to a temperature of around 925 °C (1,200 K) – the temperature prevailing in the subducted slabs beneath the western part of Pacific Ocean at the Earth’s transition zone depth. “As a result, we are able to demonstrate that the Earth’s mantle is not nearly as magnetically ‘dead’ as has so far been assumed,” says Prof. Carmen Sanchez-Valle from the Institute of Mineralogy at Münster University. “These findings might justify other conclusions relating to the Earth’s entire magnetic field,” she adds.

Relevance for investigations of the Earth's magnetic field and the movement of the poles

By using satellites and studying rocks, researchers observe the Earth’s magnetic field, as well as the local and regional changes in magnetic strength. Background: The geomagnetic poles of the Earth – not to be confused with the geographic poles – are constantly moving. As a result of this movement they have actually changed positions with each other every 200,000 to 300,000 years in the recent history of the Earth.

The last poles flip happened 780,000 years ago, and last decades scientists report acceleration in the movement of the Earth magnetic poles. Flip of magnetic poles would have profound effect on modern human civilisation. Factors which control movements and flip of the magnetic poles, as well as directions they follow during overturn are not understood yet.

One of the poles’ routes observed during the flips runs over the western Pacific, corresponding very noticeably to the proposed electromagnetic sources in the Earth’s mantle. The researchers are therefore considering the possibility that the magnetic fields observed in the Pacific with the aid of rock records do not represent the migration route of the poles measured on the Earth's surface, but originate from the hitherto unknown electromagnetic source of hematite-containing rocks in the Earth's mantle beneath the West Pacific.

“What we now know – that there are magnetically ordered materials down there in the Earth’s mantle – should be taken into account in any future analysis of the Earth’s magnetic field and of the movement of the poles,” says co-author Prof. Leonid Dubrovinsky at the Bavarian Research Institute of Experimental Geochemistry and Geophysics at Bayreuth University.

Funding:

The study received funding from the University of Münster, the German Research Foundation and the German Ministry of Education and Research.

Wissenschaftliche Ansprechpartner:

Prof. Dr. Carmen Sanchez-Valle
Institute of Mineralogy at Münster University
Phone: +49 251 83-33415
sanchezm@uni-muenster.de

Originalpublikation:

I. Kupenko et al. (2019): Magnetism in cold subducing slabs at mantle transition zone depths. Nature; DOI: 10.1038/s41586-019-1254-8

Weitere Informationen:

https://www.nature.com/articles/s41586-019-1254-8 Original publication in "Nature"

https://www.uni-muenster.de/Mineralogie/en/index.html Institute of Mineralogy at Münster University

Svenja Ronge | idw - Informationsdienst Wissenschaft
Further information:
https://www.uni-muenster.de/

More articles from Earth Sciences:

nachricht Strong storms generating earthquake-like seismic activity
16.10.2019 | Florida State University

nachricht The shelf life of pyrite
14.10.2019 | MARUM - Zentrum für Marine Umweltwissenschaften an der Universität Bremen

All articles from Earth Sciences >>>

The most recent press releases about innovation >>>

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

Im Focus: Solving the mystery of quantum light in thin layers

A very special kind of light is emitted by tungsten diselenide layers. The reason for this has been unclear. Now an explanation has been found at TU Wien (Vienna)

It is an exotic phenomenon that nobody was able to explain for years: when energy is supplied to a thin layer of the material tungsten diselenide, it begins to...

Im Focus: An ultrafast glimpse of the photochemistry of the atmosphere

Researchers at Ludwig-Maximilians-Universitaet (LMU) in Munich have explored the initial consequences of the interaction of light with molecules on the surface of nanoscopic aerosols.

The nanocosmos is constantly in motion. All natural processes are ultimately determined by the interplay between radiation and matter. Light strikes particles...

Im Focus: Shaping nanoparticles for improved quantum information technology

Particles that are mere nanometers in size are at the forefront of scientific research today. They come in many different shapes: rods, spheres, cubes, vesicles, S-shaped worms and even donut-like rings. What makes them worthy of scientific study is that, being so tiny, they exhibit quantum mechanical properties not possible with larger objects.

Researchers at the Center for Nanoscale Materials (CNM), a U.S. Department of Energy (DOE) Office of Science User Facility located at DOE's Argonne National...

Im Focus: Novel Material for Shipbuilding

A new research project at the TH Mittelhessen focusses on the development of a novel light weight design concept for leisure boats and yachts. Professor Stephan Marzi from the THM Institute of Mechanics and Materials collaborates with Krake Catamarane, which is a shipyard located in Apolda, Thuringia.

The project is set up in an international cooperation with Professor Anders Biel from Karlstad University in Sweden and the Swedish company Lamera from...

Im Focus: Controlling superconducting regions within an exotic metal

Superconductivity has fascinated scientists for many years since it offers the potential to revolutionize current technologies. Materials only become superconductors - meaning that electrons can travel in them with no resistance - at very low temperatures. These days, this unique zero resistance superconductivity is commonly found in a number of technologies, such as magnetic resonance imaging (MRI).

Future technologies, however, will harness the total synchrony of electronic behavior in superconductors - a property called the phase. There is currently a...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

VideoLinks
Industry & Economy
Event News

International Symposium on Functional Materials for Electrolysis, Fuel Cells and Metal-Air Batteries

02.10.2019 | Event News

NEXUS 2020: Relationships Between Architecture and Mathematics

02.10.2019 | Event News

Optical Technologies: International Symposium „Future Optics“ in Hannover

19.09.2019 | Event News

 
Latest News

Energy Flow in the Nano Range

18.10.2019 | Power and Electrical Engineering

MR-compatible Ultrasound System for the Therapeutic Application of Ultrasound

18.10.2019 | Medical Engineering

Double layer of graphene helps to control spin currents

18.10.2019 | Physics and Astronomy

VideoLinks
Science & Research
Overview of more VideoLinks >>>