Keith Koper, University of Utah
The surface of Earth’s inner core may be changing, as shown by a new study led by University of Southern California and University of Utah scientists that detected structural changes near the planet’s center, published Monday in Nature Geoscience.
The changes of the inner core have long been a topic of debate for scientists. However, most research has been focused on assessing rotation. John Vidale, Dean’s Professor of Earth Sciences at the USC Dornsife College of Letters, Arts and Sciences and principal investigator of the study, said the researchers “didn’t set out to define the physical nature of the inner core.”
“What we ended up discovering is evidence that the near surface of Earth’s inner core undergoes structural change,” Vidale said. The finding sheds light on the role topographical activity plays in rotational changes in the inner core that have minutely altered the length of a day and may relate to the ongoing slowing of the inner core.
Redefining the inner core
Located 3,000 miles below the Earth’s surface, the inner core is anchored by gravity within the molten liquid outer core. Until now the inner core was widely thought of as a solid sphere.
The original aim of the research team, which included U seismologist Keith Koper, was to further chart the slowing of the inner core. Their previous findings used seismic data to document how the solid core’s rotation has sped up and slowed in relation to Earth’s rotation, which may be slightly altering the length of a day.
“We found that there were some very subtle differences in these seismic waves interacting with the boundary of the inner core that are pretty shallow, that sample just the top of the inner core,” said Koper, a professor in Utah’s Department of Geology & Geophysics. “Because we had established already that the inner core is librating and then we found it back in the same spot, then these differences couldn’t be due to just the change in rotation. It must be a new thing.”
That new thing appears to be alterations in the core’s shape, according to the new study.