The inner-core of Earth is simultaneously melting and freezing due to circulation of heat in the overlying rocky mantle, according to researchers. Their findings could help scientists understand how the inner-core formed and how the outer-core acts as a 'geodynamo' which generates our planet's magnetic heat.
Study co-author Dr Jon Mound, from the University of Leeds, said: 'The origins of Earth's magnetic field remain a mystery to scientists.
'We can't go and collect samples from the centre of the Earth, so we have to rely on surface measurements and computer models to tell us what's happening in the core.'
Earth's inner-core is a ball of solid iron about the size of the moon. This ball is surrounded by a highly dynamic outer-core consisting mostly of a liquid iron-nickel alloy, a highly-viscous mantle and a solid crust that forms the surface where we live.
Over billions of years, Earth has cooled from the inside-out, causing the molten iron core to partly freeze and solidify.
The inner-core has subsequently been growing at the rate of around 1mm a year as iron crystals freeze and form a solid mass.
Dr Mound said: 'Our new model provides a fairly simple explanation to some of the measurements that have puzzled scientists for years.
'It suggests that the whole dynamics of Earth's core are in some way linked to plate tectonics, which isn't at all obvious from surface observations.
'If our model is verified it's a big step towards understanding how the inner-core formed, which in turn helps us understand how the core generates Earth's magnetic field.'
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