Scientists have just discovered a mysterious, previously unknown source of magnetism located deep inside the Earth.
There’s a previously undetected source of magnetism located inside our planet’s hottest and squishy mystery.
The discovery is kind of surprising as scientists were convinced until now that our planet’s mantle—stretching from 35 to 2,900 kilometers below the Earth’s surface—was “magnetically dead.”
But scientists from Germany, France, Denmark, and the USA have managed to prove long-standing theories wrong.
They have demonstrated that hematite, a form of iron oxide manages to retain its magnetic properties even deep inside pour planet.
This phenomenon takes place in cold tectonic plates dubbed slabs.
While they are found everywhere on Earth, their present is great beneath the western Pacific Ocean.
A strange world beneath our feet
“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,” reveals mineral physicist and first author Dr. Ilya Kupenko from the University of Münster (Germany).
Deep inside our planet’s metallic core, there is a form of liquid iron alloy that triggers the electric flows. In the outermost crust of the Earth, the rocks produce a magnetic signal. In the deepest regions of the interior of the Earth, however, it was argued that rocks come to lose their magnetic properties due to high temperatures and pressures.
Scientists closely analyzed the main potential sources of magnetism in the Earth’s mantle: iron oxides, which have a high critical temperature, that is, the temperature above which the material is no longer magnetic.
In the mantle of the Earth, the iron oxides are produced in the slabs that are buried from the earth’s crust to the interior of the mantle, as a result of the tectonic changes, a process scientists call subduction.
Scientists have found that they can reach a depth within the interior of the Earth between 410 and 660 kilometers, the so-called transition zone between the upper and lower mantle of the Earth.
This is important as no previous studies managed to measure the magnetic properties of iron oxides in the extreme conditions of pressure and temperature found in this region.
By using two new scientific methods scientists made unprecedented discoveries.
Using a so-called diamond anvil cell, the scientists managed to squeeze micron-sized samples of iron oxide hematite between two diamonds.
They then heated them with lasers to achieve pressures of up to 90 gigapascals and temperatures of more than 1,000 ° C (1,300 K).
The researchers combined this method with the so-called Mössbauer spectroscopy in order to test the magnetic state of the samples by means of synchrotron radiation.
This part of the study was carried out in the facilities of the ESRF synchrotron in Grenoble, France, and allowed scientists to finally observe the alterations of the magnetic order inside the iron oxide.
They discovered surprising results.
The study published in the journal Nature reveals how the hematite remained magnetic up to a temperature of about 925 ° C (1,200 K), the temperature prevailing in the slabs subducted below the western part of the Pacific Ocean in the depth of the transition zone of the Earth.
“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,” explains 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 added.
As explained by scientists in a statement from WWU Munster, the new discoveries may be especially relevant to future observations of magnetic anomalies on Earth and on other planets such as Mars.