[Rockhounds] New findings on the Earth's core

[Kreigh Tomaszewski]

*The Earth moves far under our feet: A new study shows that the inner core
oscillates*

USC scientists have found evidence that the Earth's inner core oscillates,
contradicting previously accepted models that suggested it consistently
rotates at a faster rate than the planet's surface.

Their study, published today in *Science Advances*, shows that the inner
core changed direction in the six-year period from 1969–74, according to
the analysis of seismic data. The scientists say their model of inner core
movement also explains the variation in the length of day, which has been
shown to oscillate persistently for the past several decades.

"From our findings, we can see the Earth's surface shifts compared to its
inner core, as people have asserted for 20 years," said John E. Vidale,
co-author of the study and Dean's Professor of Earth Sciences at USC
Dornsife College of Letters, Arts and Sciences. "However, our latest
observations show that the inner core spun slightly slower from 1969–71 and
then moved the other direction from 1971–74. We also note that the length
of day grew and shrank as would be predicted.

"The coincidence of those two observations makes oscillation the likely
interpretation."

https://phys.org/news/2022-06-earth-feet-core-oscillates.html


*The Length of a Day Oscillates Every 6 Years, And We May Finally Know Why*

How we think about our planet's center may need to be seriously updated.

New evidence suggests that, instead of consistently rotating faster than
Earth's spin, the solid inner core oscillates – spinning first in one
direction with respect to the surface far above, then the other, changing
direction every six years.

This not only has implications for our understanding of the inner workings
of our home world, it can also neatly explain a mystery that has perplexed
scientists for some time: an oscillating variation in the length of Earth's
day
<https://www.sciencedirect.com/science/article/abs/pii/S0012821X06000872>,
with a period of 5.8 years.

"From our findings, we can see the Earth's surface shifts compared to its
inner core, as people have asserted for 20 years," said geophysicist John
E. Vidale <https://www.eurekalert.org/news-releases/955427> of the
University of Southern California, Los Angeles (UCLA).

"However, our latest observations show that the inner core spun slightly
slower from 1969-71 and then moved the other direction from 1971-74. We
also note that the length of a day grew and shrank as would be predicted.
The coincidence of those two observations makes oscillation the likely
interpretation."

https://www.sciencealert.com/an-oscillating-inner-core-could-be-changing-the-length-of-earth-s-days