But what actually lies beneath our feet remains a mystery – even today we know more about Saturn’s rings than about the interior of our planet. Over the last 30 years, however, our understanding of the Earth’s inner core has expanded dramatically and has proven to move and change over the decades. But while it was previously thought to rotate at a steadily faster rate than the planet’s surface, a new study shows it oscillates, going back and forth over a mile every six years. The cycle could explain the fluctuations over the days, which have been shown to fluctuate steadily in recent decades. USC researchers have identified a six-year cycle of super- and sub-rotation in the Earth’s inner core, in contrast to previously accepted models that suggested it rotates steadily at a faster rate than the planet’s surface
FOUR LAYERS OF PLANET EARTH
Bark: At depths of up to 70 km, this is the outermost layer of the Earth, covering both ocean and land.
Mantle: Descending to 2,890 km with the lower mantle, this is the thickest layer on the planet and consists of silicate rocks richer in iron and magnesium than the crust above the head.
Outer core: From a depth of 2,890-5,150 km, this area is made of liquid iron and nickel with traces of lighter elements.
Inner core: Descending to a depth of 6,370 kilometers in the center of planet Earth, this region is considered to be composed of solid iron and nickel. But this new study shows that it contains both porridge and hard iron.
The Earth’s inner core is a hot, dense sphere of solid iron the size of Pluto – and as hot as our sun.
It is impossible to observe directly, which means that researchers must rely on indirect measurements to explain the pattern, speed and cause of movement and its changes.
The U.S. team used seismic data from 1969 to 1974 to create a computer model of nuclear motion.
The simulations confirmed the displacements of the Earth’s surface compared to its inner core, as scientists have been claiming for 20 years.
However, it contradicts previous theories that suggest that the rate of rotation was consistently faster than the surface of the planet.
“The inner core is not stable – it moves under our feet and seems to go a few miles (1.25 miles) every six years,” said lead author Professor John Vidale of the University of Southern California.
A study published in 1996 was the first to suggest that the inner core rotates faster than the rest of the planet – also known as super-rotation – at about 1 degree per year.
Subsequent findings by Professor Vidale reinforced the idea that the inner core was super-rotating, albeit at a slower rate.
Using data from LASA (Large Aperture Seismic Array), a U.S. Air Force facility in Montana, Professor Vidale found that the inner core rotates about 0.1 degrees per year.
Laboratory staff developed a new beam-forming technique for analyzing waves generated by Soviet underground nuclear bomb tests from 1971 to 1974 in the Arctic archipelago of Novaya Zemlya.
The latest results came when they applied the same methodology to a pair of previous individual trials under the island of Amchitka at the top of the Alaskan archipelago – Milrow in 1969 and Cannikin in 1971.
Measuring the compressive waves generated by the nuclear explosions, they found that the inner core was reversed, reversing at least a tenth of a degree a year.
“Our most recent observations show that the inner core rotated slightly more slowly from 1969-71 and then moved in the other direction from 1971-74,” said Professor Vidale.
We also note that the length of the day increased and decreased as expected.
“The coincidence of these two observations makes oscillation the possible interpretation.”
Because the Earth’s inner core is so inaccessible, researchers had to rely on the only means available to explore the Earth’s innermost Earth – seismic data (stock image)
Map A shows the position of the LASA (triangle) and the two nuclear test pairs (stars). B and C show the distribution of predicted time shifts
This is the first time that a six-year oscillation is indicated by direct seismic observation.
Using seismic data from atomic tests in previous studies, the researchers were able to determine the exact location and time of the seismic event.
“The idea that the inner core oscillates was a model that was out there, but the community is divided over whether it was viable,” said Professor Vidale.
“We did this expecting to see the same direction and pace of rotation in the previous pair of individual tests, but instead we saw the opposite.
“We were very surprised to find that he was moving in the other direction.
LASA closed in 1978, and the era of US underground atomic tests is over, which means researchers will have to rely on relatively inaccurate earthquake data for future research in this area, even with recent advances in instruments.
However, the study supports the hypothesis that the inner core oscillates based on fluctuations in day length – plus or minus 0.2 seconds in six years – and geomagnetic fields, which fit the theory in both amplitude and phase. .
Vidale said the findings provide a fascinating theory of the many questions posed by the research community.
“One of the questions we tried to answer is, is the inner core moving progressively or is it mostly locked compared to anything else in the long run?
“We are trying to understand how the inner core was formed and how it moves over time – this is an important step in better understanding this process.”
The study is published in Science Advances.
THE EARTH’S LIQUID IRON CREAM CREATES THE MAGNETIC FIELD
The planet’s magnetic field is believed to be created deep in the Earth’s core.
No one has ever traveled to the center of the Earth, but by studying the shock waves from earthquakes, physicists have been able to calculate its possible structure.
At the heart of the Earth is what is believed to be its solid inner core, two-thirds the size of the moon, and is made up mostly of iron. However, this new study disputes this.
At 5,700 ° C, this iron is as hot as the surface of the Sun, but the crushing pressure caused by gravity prevents it from becoming liquid.
Around it is the outer core, which is a layer 1,242 miles (2,000 km) thick of iron, nickel and small amounts of other metals.
The metal here is fluid, due to the lower pressure from the inner core.
Differences in temperature, pressure, and composition in the outer core cause transfer currents to the molten metal as cool, dense matter sinks and hot matter increases.
The “Coriolis” force, caused by the rotation of the Earth, also causes swirling vortices.
This flow of liquid iron creates electric currents, which in turn create magnetic fields.
The charged metals passing through these fields continue to generate their own electric currents and so the cycle continues.
This self-sustaining loop is known as geodynamic.
The spiral motion caused by the Coriolis force means that the individual magnetic fields are roughly aligned in the same direction, with their combined effect creating a huge magnetic field that floods the planet.
