Recently, seismologists have observed that the speed and direction of seismic waves in Earth’s lower mantle, between 400 and 1,800 miles below the surface, vary tremendously. “I think we may have discovered why the seismic waves travel so inconsistently there,” stated Jung-Fu Lin.* Lin was with the Carnegie Institution’s Geophysical Laboratory at the time of the study and lead author of the paper published in the July 21, issue of Nature. “Until this research, scientists have simplified the effects of iron on mantle materials. It is the most abundant transition metal in the planet and our results are not what scientists have predicted,” he continued. “We may have to reconsider what we think is going in that hidden zone. It’s much more complex than we imagined.”