The inner core, made of very pure, solid iron, rotates along with the outer core, dragging the Earth's magnetic field with them.
The sediment layer would have to be less than a km (half a mile) thick in order to have the observed effect, and would probably cover only patches of the outer core.
The origin of this effect may lie at the boundary between the mantle, made up of viscous rock that extends 2, 900 km (1, 800 miles) below the crust, and the outer core, which is thought to be liquid iron with the consistency of water.
The research could help test simulations of how the outer, fluid core generates the Earth's magnetic field, which shields our planet and the teeming life on it from harmful cosmic rays.
BBC: NEWS | Science/Nature | Earth's core runs ahead of crust
The result is not unlike what you get when you broil a steak: a darkened, cooked outer layer, with a lighter core.
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If the star's outer layers could be mixed into the core, that would slow the process of inflation down.
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Japanese researchers say the basalt in NWA 011 suggests the body from which it did originate had a core of molten iron with an outer covering of silicon and aluminium that formed a basaltic crust.
The castle's walls will consist of inner and outer layers of stone, sandwiching a reinforced concrete core.
The outer layer, or cladding, is plain silica, while the core is doped with germanium.
Red giants are created when a star exhausts its supply of hydrogen at its core, with the result that the inner layer contracts and the outer layers expand, forming a redder and much larger star.
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Their business is driven by the symbiotic alliance between the Net's outer edge, where individual users log on by the millions, and its inner core, where the big traffic moves.
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