Livescience editor Rob Roy Britt examines some of the new findings & new ideas on the Earth's internal composition, being releases in Science magazine. The old core, mantle and crust structure theory has been shown to be a tad simplistic.
The crust extends from the surface to a depth of about 25 miles surrounding the mantle, an area of hot silicate rock, now divided into the upper and lower mantles, extending to a depth of around 1800 miles. Deeper yet is the nickel-iron core, which can also be further discriminated into an outer and inner core region. Some of the new analysis shows the mantle is composed of slightly different material than initially believed, with two large 'blobs' of chemically distinct materials on each side of the planet, one under the Pacific and the other under the Atlantic and Africa. An ASU researcher describes it this way:
"Imagine a pot of water boiling," explains researcher Allen McNamara of Arizona State University. "That would be all one kind of composition. Now dump a jar of honey into that pot of water. The honey would be convecting on its own inside the water and that's a much more complicated system."
The new theories regarding the Earth's interior composition help explain the quite curious way seismic waves travel through the Earth when an event occurs, with the waves making unexplained speed changes as they travel throught the planet.