Secrets of Earth's Inner Core

The Earth’s inner core is a solid ball the size of the Moon, made of iron and nickel, surrounded by an outer core of flowing liquid iron alloy. As no direct samples of the inner core, outer core and of the mantle can be taken, our knowledge of their structure and properties relies on seismology, the only tool that allows us to “see through” the Earth. Seismometers measure the waves generated by earthquakes and these data are interpreted to evaluate the Earth’s composition, density and velocity.

Credit: © Deuss et al. Regional Variation of Inner Core Anisotropy from Seismic
Normal Mode Observations. Science (2010) vol. 328 (5981) pp. 1018-1020

Life on Earth is possible thanks to its magnetic field that protects us from cosmic radiation and is generated by the core, which is the very central structure of our planet. Studying the composition and thermal state of the Earth’s deep interior is key to unraveling how its magnetic field works.

In her project, Dr Deuss coupled seismic observations of whole Earth oscillations, which make the Earth ring like a bell, with expertise in fluid dynamics and mineral physics. Her team developed pioneering tools to focus on some specific deep parts of our planet, something which had not been possible before due to lack of appropriate theory. Applying this novel theory and analyzing data from large earthquakes all around the globe – including the 2011 devastating seismic event in Japan – the team made a new comprehensive model of the inner core leading to several exciting discoveries.

Dr Deuss’ work has shown that the top of the inner core is divided into two hemispheres with very sharp boundaries. They are so different that they might be the equivalent of the continental and oceanic regions on the Earth’s surface – limiting the phenomenon of inner core superrotation to less than one degree per million years.