New Research Shows the Earth’s Inner Core Oscillates – Causes Variation in the Length of a Day

Earth Core Structure

Scientists have discovered evidence that the Earth’s inner core oscillates, contradicting previously held beliefs that it consistently rotates at a faster rate than the planet’s surface.

Scientists identify a six-year cycle of super- and sub-rotation that affected the length of a day based on their analysis of seismic data.

Earth’s structure is divided into layers, with the inner core at the center followed by the outer core, lower mantle, upper mantle, crust, and atmosphere. The inner core is the hottest part of the planet at about 10,000 °F (5400 °C), which is similar to the temperature of the surface of the sun!

Believed to consist mostly of an iron-nickel alloy, the inner core is mainly a solid ball with a radius of about 760 miles (1,220 km). It rotates slightly faster than the planet as a whole, which is called super-rotation.

University of Southern California (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 (June 10, 2022) in the journal 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 a 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 a day grew and shrank as would be predicted.

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

Earth’s Oscillating Inner Core

USC researchers identified a six-year cycle of super- and sub-rotation in the Earth’s inner core, contradicting previously accepted models that suggested it consistently rotates at a faster rate than the planet’s surface. Credit: Edward Sotelo/USC

Analysis of atomic tests pinpoints rotation rate and direction

Our understanding of the inner core has expanded dramatically in the past 30 years. The inner core — a hot, dense ball of solid iron the size of Pluto — has been shown to move and/or change over decades. It’s also impossible to observe directly, meaning researchers struggle through indirect measurements to explain the pattern, speed and cause of the movement and changes.

Research published in 1996 was the first to propose that the inner core rotates faster than the rest of the planet — also known as super-rotation — at roughly 1 degree per year. Subsequent findings from Vidale reinforced the idea that the inner core super-rotates, albeit at a slower rate.

Earth's Layers Structure Infographic

Earth’s layers and structure.

Utilizing data from the Large Aperture Seismic Array (LASA), a U.S. Air Force facility in Montana, researcher Wei Wang and Vidale found the inner core rotated slower than previously predicted, approximately 0.1 degrees per year. The study analyzed waves generated from Soviet underground nuclear bomb tests from 1971-74 in the Arctic archipelago Novaya Zemlya using a novel beamforming technique developed by Vidale.

The new findings emerged when Wang and Vidale applied the same methodology to a pair of earlier atomic tests beneath Amchitka Island at the tip of the Alaskan archipelago — Milrow in 1969 and Cannikin in 1971. Measuring the compressional waves resulting from the nuclear explosions, they discovered the inner core had reversed direction, sub-rotating at least a tenth of a degree per year.

This latest study marked the first time the well-known six-year oscillation had been indicated through direct seismological observation.

“The idea the inner core oscillates was a model that was out there, but the community has been split on whether it was viable,” Vidale says. “We went into this expecting to see the same rotation direction and rate in the earlier pair of atomic tests, but instead we saw the opposite. We were quite surprised to find that it was moving in the other direction.”

Future research to dig deeper into why inner core formed

Vidale and Wang both noted future research would depend on finding sufficiently precise observations to compare against these results. By using seismological data from atomic tests in previous studies, they have been able to pinpoint the exact location and time of the very simple seismic event, says Wang. However, the Montana LASA closed in 1978 and the era of U.S. underground atomic testing is over, meaning that the researchers would need to rely on comparatively imprecise earthquake data, even with recent advances in instrumentation.

The study does support the speculation that the inner core oscillates based on variations in the length of day — plus or minus 0.2 seconds over six years — and geomagnetic fields, both of which match the theory in both amplitude and phase. Vidale says the findings provide a compelling theory for many questions posed by the research community.

“The inner core is not fixed — it’s moving under our feet, and it seems to be going back and forth a couple of kilometers every six years,” Vidale said. “One of the questions we tried to answer is, does the inner core progressively move or is it mostly locked compared to everything else in the long term? We’re trying to understand how the inner core formed and how it moves over time — this is an important step in better understanding this process.”

Reference: “Seismological observation of Earth’s oscillating inner core” by Wei Wang and John E. Vidale, 10 June 2022, Science Advances.
DOI: 10.1126/sciadv.abm9916

10 Comments on "New Research Shows the Earth’s Inner Core Oscillates – Causes Variation in the Length of a Day"

  1. Please also give information about autoimmune diseases
    How many diseses uptil now ie numbers
    Small difinition of every disease
    Later on cover each health topics
    Pl also give all information about zoology

  2. Lenny Schafer | June 11, 2022 at 6:40 am | Reply

    Wait! I just read somewhere that the earth is flat. How can this be?

  3. Como se mueve el núcleo de la tierra no es que no existe el movimiento perpetuo?

  4. It appears either scitechdaily is in need of an editor or (s)he’s getting paid too much; there’s typos on the page, tsk, tsk, tsk.

  5. That is very interesting. I can’t believe that there are people who actually think the world is flat. Let them try and debunk this article.. it would probably take a flat earther no more that 18 seconds to do it.

  6. Servant of The Great I AM | June 22, 2022 at 8:48 am | Reply

    This article further proves the intelligence of THE GREAT I AM.
    The earth(land) like the Bible states in exodus. The celestial home we reside in is circular with land and water. I AM spoke this home into creation thus his mighty voice is the frequency of said oscillation and vibration(sitting still like a pillar a firm foundation.) The celestial home is massive beyond anything a man could measure, it’s immeasurable( book of Job.)
    The human eye is seeing the earth as a ball or sphere because of the bending (relativity) of light in space time. In short, we ARE HOVERING IN SPACE, so how can you go to space when we are ALREADY there?
    Gravity is God at rest. Once he moves to Judge the inhabited earth that is full of iniquities all things of the universe will be made new. And the very throne which he resides is in our celestial planetary system (the one body) with Jesus. It took me 45 years to understand this knowledge( hidden manna) not 18 seconds.

  7. I’ve always sworn the days were shorter since I moved to Iowa eight years ago. /s

  8. So how’s Earth’s core spin faster than the crust outpacing it as it’s got friction on all sides. Change direction even. Where’s the energy to do that come from and why is heavy stuff spinning and in the center when they so n stuff to make the heavier parts go to the outside and lighter things stay closer to the center?

  9. If Earth’s core dictates it’s EMF. Wouldn’t that reverse of the core be really bad as it transitions. Like pole reversal bad. It is everything they claim makes our magnetic field moving completely different from time to time in very short periods of time….

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