Watch a video about how Earth’s inner core changes shape over time, from the University of Southern California.
Earth’s inner core is less solid than we once thought
Earth’s inner core lies some 3,000 miles (4,800 km) below our world’s surface. Scientists long thought the inner core was a solid sphere. But new research shows it’s not perfectly solid. Its surface changes shape over time due to interactions with the outer molten core.
In this study, scientists analyzed seismic waves – vibrations that move through the Earth – generated by earthquakes. They studied seismic waves from 120 earthquakes, most originating at known faults at Antarctica’s South Sandwich Islands, between 1991 and 2024.
The waves these earthquakes generated traveled through the center of the Earth. Then seismographs picked them up almost on the other side of the world, in Fairbanks, Alaska and Yellowknife, Canada.
Researchers published their findings in the peer-reviewed journal Nature Geoscience on February 10, 2025.
An unexpected discovery
The original purpose of the study was to better characterize the rotation of the Earth’s inner core, which is about 1,520 miles (2,440 km) in diameter. Scientists once thought the solid inner core rotated at the same rate as the rest of Earth. Then, studies about two decades ago suggested it may have been rotating a bit faster.
However, in June 2024, the same team behind this new study confirmed the inner core’s rotation had been slowing down since 2010. Therefore, they wanted to use the South Sandwich Islands earthquake data to continue studying the rotation.
Lead author John Vidale of USC Dornsife said:
But as I was analyzing multiple decades’ worth of seismograms, one dataset of seismic waves curiously stood out from the rest. Later on, I’d realize I was staring at evidence the inner core is not solid.
He said he was initially puzzled by the one dataset from Yellowknife, Canada. But as his team refined their analysis of those seismic waves, they realized they were seeing physical activity in the inner core.
What’s causing changes to the inner core?
The scientists think they’re seeing changes over time in the shape of the inner core’s outer boundary. It could be due to interactions between the inner and outer core. Vidale commented:
The molten outer core is widely known to be turbulent, but its turbulence had not been observed to disrupt its neighbor, the inner core, on a human timescale. What we’re observing in this study for the first time is likely the outer core disturbing the inner core.
He added that this discovery could help scientists better understand the dynamics of Earth’s core, as well as our planet’s thermal properties and magnetic field.
Bottom line: Scientists report that Earth’s inner core is not perfectly solid. Its surface changes shape over time due to interactions with the outer molten core.
Source: Annual-scale variability in both the rotation rate and near surface of Earth’s inner core
Via University of Southern California
Read more: Earth’s core has a huge, hidden donut shape
The post Earth’s inner core changes shape over time first appeared on EarthSky.
from EarthSky https://ift.tt/kP517ug
Watch a video about how Earth’s inner core changes shape over time, from the University of Southern California.
Earth’s inner core is less solid than we once thought
Earth’s inner core lies some 3,000 miles (4,800 km) below our world’s surface. Scientists long thought the inner core was a solid sphere. But new research shows it’s not perfectly solid. Its surface changes shape over time due to interactions with the outer molten core.
In this study, scientists analyzed seismic waves – vibrations that move through the Earth – generated by earthquakes. They studied seismic waves from 120 earthquakes, most originating at known faults at Antarctica’s South Sandwich Islands, between 1991 and 2024.
The waves these earthquakes generated traveled through the center of the Earth. Then seismographs picked them up almost on the other side of the world, in Fairbanks, Alaska and Yellowknife, Canada.
Researchers published their findings in the peer-reviewed journal Nature Geoscience on February 10, 2025.
An unexpected discovery
The original purpose of the study was to better characterize the rotation of the Earth’s inner core, which is about 1,520 miles (2,440 km) in diameter. Scientists once thought the solid inner core rotated at the same rate as the rest of Earth. Then, studies about two decades ago suggested it may have been rotating a bit faster.
However, in June 2024, the same team behind this new study confirmed the inner core’s rotation had been slowing down since 2010. Therefore, they wanted to use the South Sandwich Islands earthquake data to continue studying the rotation.
Lead author John Vidale of USC Dornsife said:
But as I was analyzing multiple decades’ worth of seismograms, one dataset of seismic waves curiously stood out from the rest. Later on, I’d realize I was staring at evidence the inner core is not solid.
He said he was initially puzzled by the one dataset from Yellowknife, Canada. But as his team refined their analysis of those seismic waves, they realized they were seeing physical activity in the inner core.
What’s causing changes to the inner core?
The scientists think they’re seeing changes over time in the shape of the inner core’s outer boundary. It could be due to interactions between the inner and outer core. Vidale commented:
The molten outer core is widely known to be turbulent, but its turbulence had not been observed to disrupt its neighbor, the inner core, on a human timescale. What we’re observing in this study for the first time is likely the outer core disturbing the inner core.
He added that this discovery could help scientists better understand the dynamics of Earth’s core, as well as our planet’s thermal properties and magnetic field.
Bottom line: Scientists report that Earth’s inner core is not perfectly solid. Its surface changes shape over time due to interactions with the outer molten core.
Source: Annual-scale variability in both the rotation rate and near surface of Earth’s inner core
Via University of Southern California
Read more: Earth’s core has a huge, hidden donut shape
The post Earth’s inner core changes shape over time first appeared on EarthSky.
from EarthSky https://ift.tt/kP517ug
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