(ORDO NEWS) — For the first time, scientists have properly considered the zone of ultra-low speeds. These mysterious pockets of rock lie near the Earth‘s core, about 3,000 kilometers (1,864 miles) below the surface.
At this depth, they are difficult to study, but we know they are there because of the way seismic waves travel through the Earth. These zones get their name from the fact that seismic waves slow down as they pass through them.
Until now, the images of these zones have been grainy and difficult to analyze, but the images published in the new study depict the zone under Hawaii in much more detail, which allows us to take a fresh look at the internal structure of our planet and its history.
“Of all the deep interior of the Earth, these objects are the most interesting and complex,” says geophysicist Zhi Li from the University of Cambridge (UK).
“Now we have the first convincing evidence of their internal structure – this is a real milestone in the deep seismology of the Earth.”
To create the image, the latest computational modeling techniques were used, which were applied to a high-frequency signal that was recorded as seismic waves passed through a zone of ultra-low velocities.
This allows experts to look at a pocket of rock on a kilometer scale, increasing resolution by an order of magnitude when studying the boundary between the Earth’s iron-nickel core and the mantle wrapped around it.
Hot mantle rock flows cause earthquakes, volcanoes and other activities, and scientists are interested in learning more about how ultra-low velocity zones can cause or affect this activity.
It is hypothesized that the extra iron in these unusual zones may create additional density, which manifests itself in seismic waves – and finding out this or that fact can tell us more about how the Earth formed and how its core works today.
“It is possible that this iron-rich material is a remnant of ancient rocks from Earth’s early history, or even that iron may be seeping out of the core in an unknown way,” says seismologist Sanne Kottaar of the University of Cambridge.
Scientists have also noticed links between ultra-low velocity zones and volcanic vents such as those in Hawaii and Iceland. According to one hypothesis, these hot spots may be caused by the ejection of material from the core to the surface.
Improved images of these deep and mysterious zones should help in this area of research as well, and scientists are also studying surface basalt rocks in Hawaii looking for evidence of a core leak.
The study of ultra-low velocity zones is limited in some respects to where earthquakes occur and where seismographs are installed, but the team is interested in applying their high-resolution imagery to other deep regions of the Earth.
“We’re really pushing the boundaries of today’s HPC for elastodynamic simulations by taking advantage of wave symmetries that have not been seen or exploited before,” says data scientist Kuangdai Leng of the University of Oxford in the UK.
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