Snow is usually a traditional feature of the holiday season. We see it represented everywhere: in adverts, movies, music videos, and now it appears even the hot core of the Earth is getting in the festive spirit with its own delivery of "snow". These white water-ice flakes are much heavier than snowflakes, though, because they are made of tiny particles of iron.
Since we can't actually sample Earth's core, researchers study the seismic waves that pass through Earth. Reporting in the Journal of Geophysical Research Solid Earth, a team observed some peculiarities in the propagation of seismic waves as they move through the inside of our planet, compared to the current model of Earth's core. Seismic waves moved faster than expected going through the eastern hemisphere of the top inner core, and more slowly at the base of the outer core.
In the study, the team suggests that this can be explained by a flurry of iron crystals accumulating on the boundary between the inner and outer core. This coating is not even all way around and the researchers showed in the lab that certain iron alloys can crystalize in similar conditions to the outer core.
“It’s sort of a bizarre thing to think about,” co-author Nick Dygert from the University of Texas, said in a statement. “You have crystals within the outer core snowing down onto the inner core over a distance of several hundred kilometers.”
The team compared the process happening within Earth's metallic core as similar to magma chambers closer to the surface of our planet. Crystals can form within the magma and as they glom together, they form the so-called cumulate rocks.
The process is taking away material from the outer core and depositing in the inner core, and these changes will have profound consequences across the planet.
“The inner-core boundary is not a simple and smooth surface, which may affect the thermal conduction and the convections of the core,” lead author Youjun Zhang also from UT added.
The release of heat from the inner core shapes the motion of the mantle, which in turn affects the movement of tectonic plates. The inner core also generates the magnetic field of our planet so changes to that have truly global consequences.
If the findings are indeed correct, the work could provide insights into how the core came to be. There are still many unknowns with regard to the compositions of the inner layers of our planet. The correct explanation for the aberration could finally tell us something we don’t know.