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posted by janrinok on Tuesday June 08, @07:45PM   Printer-friendly
from the off-balance-Betteridge dept.

Is Earth's core lopsided? Strange goings-on in our planet's interior.:

For reasons unknown, Earth's solid-iron inner core is growing faster on one side than the other, and it has been ever since it started to freeze out from molten iron more than half a billion years ago, according to a new study by seismologists at the University of California, Berkeley.

The faster growth under Indonesia's Banda Sea hasn't left the core lopsided. Gravity evenly distributes the new growth — iron crystals that form as the molten iron cools — to maintain a spherical inner core that grows in radius by an average of 1 millimeter per year.

But the enhanced growth on one side suggests that something in Earth's outer core or mantle under Indonesia is removing heat from the inner core at a faster rate than on the opposite side, under Brazil. Quicker cooling on one side would accelerate iron crystallization and inner core growth on that side.

This has implications for Earth's magnetic field and its history, because convection in the outer core driven by release of heat from the inner core is what today drives the dynamo that generates the magnetic field that protects us from dangerous particles from the sun.

"We provide rather loose bounds on the age of the inner core — between half a billion and 1.5 billion years — that can be of help in the debate about how the magnetic field was generated prior to the existence of the solid inner core," said Barbara Romanowicz, UC Berkeley Professor of the Graduate School in the Department of Earth and Planetary Science and emeritus director of the Berkeley Seismological Laboratory (BSL). "We know the magnetic field already existed 3 billion years ago, so other processes must have driven convection in the outer core at that time."

(...) Asymmetric growth of the inner core explains a three-decade-old mystery — that the crystallized iron in the core seems to be preferentially aligned along the rotation axis of the earth, more so in the west than in the east, whereas one would expect the crystals to be randomly oriented.

Evidence for this alignment comes from measurements of the travel time of seismic waves from earthquakes through the inner core. Seismic waves travel faster in the direction of the north-south rotation axis than along the equator, an asymmetry that geologists attribute to iron crystals — which are asymmetric — having their long axes preferentially aligned along Earth's axis.

Journal Reference:
Daniel A. Frost, Marine Lasbleis, Brian Chandler, et al. Dynamic history of the inner core constrained by seismic anisotropy, Nature Geoscience (DOI: 10.1038/s41561-021-00761-w)

Also at Nature


Original Submission

 
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  • (Score: 2) by shortscreen on Wednesday June 09, @12:18AM (4 children)

    by shortscreen (2252) Subscriber Badge on Wednesday June 09, @12:18AM (#1143334) Journal

    Earth's solid-iron inner core is growing faster on one side

    Gravity evenly distributes the new growth — iron crystals that form as the molten iron cools

    So... the growth is uneven, but it evens out again? What exactly is lopsided?

    something in Earth's outer core or mantle under Indonesia is removing heat from the inner core at a faster rate than on the opposite side, under Brazil

    Would this be related to Indonesia being in the Pacific ring of fire, and Brazil being just a boring landmass?

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  • (Score: 0) by Anonymous Coward on Wednesday June 09, @12:58AM

    by Anonymous Coward on Wednesday June 09, @12:58AM (#1143351)

    You don't mean to say that these scientists might just have overlooked the most obvious possibility do you?

  • (Score: 0) by Anonymous Coward on Wednesday June 09, @02:06AM

    by Anonymous Coward on Wednesday June 09, @02:06AM (#1143390)

    Boring? You've just offended Brazilians around the world.

  • (Score: 0) by Anonymous Coward on Wednesday June 09, @12:20PM

    by Anonymous Coward on Wednesday June 09, @12:20PM (#1143495)

    Would this be related to Indonesia being in the Pacific ring of fire, and Brazil being just a boring landmass?

    The 11km deep Mariana Trench probably also has a significant effect on the mantle temperature, although I'm not sure if that effect is significant deeper down.

  • (Score: 1) by ChrisRev on Wednesday June 09, @01:57PM

    by ChrisRev (8698) on Wednesday June 09, @01:57PM (#1143514)
    I read that as two different meanings of the word "growth":
    1. the process of growing that happens unevenly
    2. the mass of solid iron resulting from that process, getting subsequently evened out by gravity.

    The English language is indeed confusing.