"The giant orb of iron and nickel that anchors Earth's center is
spinning faster than the planet's surface, according to a new study
that confirms scientists' expectations."
"Earth's core is made of a solid inner part and a fluid outer part, all
of it mostly iron.
The solid inner core has an uneven consistency, with some parts denser
than others, and this can either speed up or slow down shock waves from
earthquakes as they pass through.
So the researchers speculated that if the Earth's inner core is
rotating faster than the rest of the planet, then shock waves from
waveform doublets would enter and exit through different parts of the
core despite originating from roughly the same spot on the planet's
By analyzing the minute changes in travel times and wave shapes for
each doublet, the researchers concluded that the Earth's inner core is
rotating faster than its surface by about 0.3-0.5 degrees per year.
That may not seem like much, but it's very fast compared to the
movement of the Earth's crust, which generally slips around only a few
centimeters per year compared to the mantle below, said Xiaodong Song,
a geologist at the University of Illinois at Urbana-Champaign and an
author on the study."
It makes sense that the inner core should be rotating faster, since the
tidal drag from the Sun an Moon would have the most leverage on the