Wednesday, May 25, 2011

Earth Core is Melting and Freezing As Well

The inner core of Earth is simultaneously melting and freezing due to circulation of heat in the overlying rocky mantle, according to new research from the University of Leeds, UC San Diego and the Indian Institute of Technology.

"Our new model provides a fairly simple explanation to some of the measurements that have puzzled scientists for years. It suggests that the whole dynamics of Earth's core are in some way linked to plate tectonics, which isn't at all obvious from surface observations.

Earth's inner core is a ball of solid iron about the size of our moon. This ball is surrounded by a highly dynamic outer core of a liquid iron-nickel alloy (and some other, lighter elements), a highly viscous mantle and a solid crust that forms the surface where we live.

Over billions of years, Earth has cooled from the inside out causing the molten iron core to partly freeze and solidify. The heat given off as the core cools flows from the core to the mantle to Earth's crust through a process known as convection. This escaping heat powers the geo dynamo and coupled with the spinning of Earth generates the magnetic field.

Scientists have recently begun to realize that the inner core may be melting as well as freezing. They show that heat flow at the core-mantle boundary varies depending on the structure of the overlying mantle. On the other hand, melting would produce a layer of dense liquid above the boundary. Therefore, the blobs of light elements will rise through this layer before they stir the overlying outer core.

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