New research found that Earth’s core was once covered by an ancient ocean of magma, which might help scientists better understand previous discoveries seen deep within our planet.
Previous calculations done by scientists showed that about 4.5 to 2.5 billion years ago, an enormous ocean of molten rock – also referred to as magma – existed between the core of the plant and its crust. But these models had not been confirmed by experiments.
Scientists at the European Synchrotron Radiation Facility in Grenoble, France generated X-ray beams on Earth to find whether remains of the ancient ocean magma existed deep within the planet. They looked for solidified bridgmanite (silicate perovskite) – the most abundant mineral found in the lower part of Earth’s mantle.
Bridgmanite contains silicon, magnesium and oxygen atoms, which are arranged into cystaline structures. When the mineral melts it turns into magnesium-silicate melt, and its atoms form disorderly arrangements.
The amorphous structure – an arrangement that lacks a crystalline structure – of the magnesium-silicate melt makes it denser than regular bridgmanite. According to scientists, this may cause it to sink deeper within the Earth, right next to its core.
The density of the amorphous magnesium-silicate melt was measured using X-rays at extreme pressures equal to 135 gigapascals – units which geophysicists use to calculate or measure tectonic pressures and stresses within the Earth. These types of pressures can only be found at about 1,800 miles (2,900 kilometres) below the planet’s surface.
Sylvain Petitgirard, a geophysicist at the University of Bayreuth in Germany and lead author of the study, said that he along with other researchers conducted experiments on magnesium-silicate glass in which they squeezed a sample of magnesium-silicate glass (that was as thick as a human hair) between two diamonds.
The findings showed that amorphous magnesium-silicate melt may actually be denser than crystalline bridgmanite. Deep within the Earth, magnesium-silicate melts would combine with iron, resulting in a dense magma that would sink just above the Earth’s core.
Earth’s ancient magma ocean may have contained thorium and uranium, which – Petitgirard says – can be seen in rocks from Hawaii.
“A basal magma ocean would be an ideal candidate to explain [that feature]. There is really a lot of work to do to understand our planet,” Petitgirard said.
The findings were published November 2 in the online journal Proceedings of the National Academy of Sciences.
Image Source: exospace