Earth's inner core has an inner core of its own: Study

A new study revealed that the Earth's inner core has an inner core of its own, which has surprising properties that can reveal information about Earth.

The findings of the study titled Equatorial anisotropy in the inner part of Earth’s inner core from autocorrelation of earthquake coda were published in the journal Nature Geoscience on 9 February 2015.

The study was conducted by a research team led by Xiaodong Song at the University of Illinois and colleagues at Nanjing University in China with the novel application of earthquake-reading technology.

Study Process
Researchers used seismic waves from earthquakes to scan the planet's surface. The team used a technology that gathers data not from the initial shock of an earthquake, but from the Seismic Waves that resonate in the earthquake's aftermath.

The echo of seismic waves bounces around the planet after an earthquake to build up a picture of the Earth's interior.

The arrays of sensors in locations around the world including Venezuela and southeast China allowed the scientists to measure delays in the time it took for these waves to travel through the planet.

Findings of the study
• The scientists discovered that seismic waves that passed through the very centre of the planet showed interference very different from those that travelled through the rest of the core.
• Looking through the core revealed a surprise at the center of the Earth. The inner core, once thought to be a solid ball of iron, has some complex structural properties.
• The team found a distinct inner-inner core is about half the diameter of the whole inner core.
• The iron crystals in the outer layer of the inner core are aligned directionally, north-south. However, in the inner-inner core, the iron crystals point roughly east-west.
• Not only are the iron crystals in the inner-inner core are aligned differently, they also behave differently from their counterparts in the outer-inner core.