The rotation of Earth’s inner core began to slow more than a decade ago, changing the length of our days by fractions of a second.
Researchers from the University of Southern California (USC) created interpretations of movement of the inner core using seismic data recorded from various earthquakes and nuclear tests, both of which send vibrations through the planet. By measuring the speed and interaction of seismic waves within the Earth’s layers, researchers can estimate the position and movement of the inner core.
The study confirms that since 2010, Earth Internal core has been slowing down, or falling back, compared to its speed in previous decades; it is also moving more slowly than the Earth’s surface, according to a statement from USC.
“The inner core had slowed for the first time in many decades,” John Vidale, co-author of the study and professor of Earth Sciences at USC, said in the statement. “Other scientists have recently argued for similar and different models, but our latest study provides the most compelling solution.”
Connected: The Earth’s Layers: Exploring Our Planet Inside and Out
Of the Earth Internal core it is a hot, dense, hard ball made of iron and nickel, located 3,200 miles (5,150 kilometers) below our feet. It is surrounded by a liquid iron-nickel outer core, enveloped by a hard rocky mantle. The new study shows that the slowing rate of the inner core is caused by convection within the outer core of liquid iron, which supports Earth’s magnetic fieldand the pull of gravitational forces on the upper mantle.
The researchers analyzed seismic data recorded during 121 repeated earthquakes that occurred around the South Sandwich Islands in the South Atlantic between 1991 and 2023, as well as data from several nuclear tests around the globe, to reach their conclusions.
In theory, repeated earthquakes would produce identical seismograms because they occur in the same location. This is why the comparison of seismic data from different points in time can detect changes beneath the planet’s surface. Subtle changes in how long it took seismic waves to travel through earth at various times in the history of the planet revealed the slowing down of the inner core. While this difference can change the length of a day by fractions of a second, it won’t be noticeable, the researchers said.
Their findings were published on June 12 in the journal Nature.
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