Earth's innermost core discovery confirmed by Staff Writers Champaign, Ill., March 13, 2007 U.S. geologists have created a three-dimensional model describing the seismic anisotropy and texturing of iron crystals within the Earth's innermost core.

University of Illinois geologist Xiaodong Song and postdoctoral researcher Xinlei Sun discovered Earth's core, composed mainly of iron, consists of a solid inner core about 1,500 miles in diameter and a fluid outer core about 4,350 miles in diameter.

The solid inner core is elastically anisotropic; that is, seismic waves have different speeds along different directions, the scientists said.

"Our results suggest the outer inner core is composed of iron crystals of a single phase with different degrees of preferred alignment along Earth's spin axis," Sun said. "The inner, inner core may be composed of a different phase of crystalline iron or have a different pattern of alignment."

The study has been accepted for publication in the journal Earth and Planetary Science Letters, and is posted on its Web site.