
Originally Posted by
Ophiolite
I don't know where you got that quote, but it is faulty. Both the inner and outer cores spin at almost the same rate as the rest of the planet. A very slight difference in rotation rates exists between the inner and outer cores, but this was confirmed only in the last couple of weeks.
The inner core is solid, the outer core is liquid. Both are predominantly iron, with nickel and a handful of other elements. The Earth's magnetic field is generated by convection currents in the outer core.
Edited to correct errant typography.