Seismologists at the University of California, Berkeley, who have been investigating the phenomenon, say it grows faster under the Banda Sea in Indonesia than in Brazil, but this uneven growth pattern hasn’t left the core unbalanced.
Gravity evenly distributed the new growth of iron crystals that form when molten iron begins to cool, maintaining a spherical inner core.
The team said that although it does not leave the core unbalanced, the uneven growth rate indicates that something in the outer core under Indonesia is removing heat from the inner core at a faster rate than it is under Brazil, on the other side of the planet.
The researchers say that this discovery helped them “prove that there are fairly loose limits” for the age of the inner core, to between half a billion and 1.5 billion years.
These limits on the age of Earth’s hard core could help scientists learn more about the magnetic field, which protects us from harmful solar radiation.
The Earth’s interior consists of layers like “onion slices”, where the radius of the solid inner core of iron and nickel is 745 miles, or about three-quarters the size of the moon, and is surrounded by a liquid outer core of molten iron and nickel about 1,500 miles thick. The outer core is surrounded by a blanket of hot rock 1,800 miles thick, with a thin, cold rock crust at the surface.
The strong boiling motion of the outer core produces the Earth’s magnetic field.