Scientists say they have identified a new feature in Earth’s molten outer core.
They describe it as a ‘jet stream’ – a fast-flowing river of liquid iron that surges westwards under Alaska and Siberia.
The moving mass of metal has been inferred from measurements made by Europe’s Swarm satellites.
This trio of spacecraft are currently mapping Earth’s magnetic field to try to understand its fundamental mechanisms.
The scientists say the jet is the best explanation for the patches of concentrated field strength that the satellites observe in the northern hemisphere.
Dr Chris Finlay from the National Space Institute at the Technical University of Denmark (DTU Space), said: “This jet of liquid iron is moving at about 50 kilometres per year.
“That might not sound like a lot to you on Earth’s surface, but you have to remember this a very dense liquid metal and it takes a huge amount of energy to move this thing around, and that’s probably the fastest motion we have anywhere within the solid Earth.”
Phil Livermore from Leeds University, UK, and the lead author on the journal paper, said: “It’s likely that the jet stream has been in play for hundreds of millions of years.”
The scientists say the feature probably aligns to a boundary between two different regions in the core.
Although the team believes it understands how wide and how long the jet is, the depth to which it descends is far from certain.
Livermore added: “It currently wraps about 180 degrees around the tangent cylinder. Although observations only constrain the jet stream on the edge of the core, our theoretical understanding suggests that the jet could, in principle, go very deep indeed – possibly in fact all the way down to the edge of the core in the southern hemisphere (i.e. at the other end of the tangent cylinder).”
Finlay was speaking at the American Geophysical Union (AGU) meeting in San Francisco, US, ahead of the official publication of the research in the journal Nature Geoscience.