The Earth's core may not at all be like what scientists have led us to believe.

Geologists have discovered that the Earth's inner core - previously thought to be a solid lump of iron - may in fact have its own even smaller core within it.

Using the seismic waves that reverberate across the planet after earthquakes, researchers have been able to gain new insight into what lies at the centre of our world.

The findings could mean that our understanding of Earth's interior, and its history, will need to be rewritten.

Scientists found that rather than a solid ball of iron lying within the molten mass of the outer core, the inner core changes in structure about half way through.

They discovered a distinct inner inner core that is about half the diameter of what was believed to be the solid inner core, which is about the size of the moon.

Read more here:http://phys.org/news/2015-02-earth-geologists-mysteries-planet-core.html

University of Illinois
Earth's surprise inside: Geologists unlock mysteries of the planet's inner core
http://news.illinois.edu/news/15/0209innercore_XiaodongSong.html