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Earth's inner core is melting and freezing at same time, says IITian

Washington , Thu, 19 May 2011 ANI

Washington, May 19 (ANI): A study involving an Indian-origin researcher has found that the inner core of Earth is melting and freezing at the same time, overturning the long established notion that it has only been freezing.


The findings could help us understand how the inner core formed and how the outer core acts as a 'geodynamo', which generates the planet's magnetic field.


The 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.


However, there has been much debate about how this is possible when overall the deep Earth is cooling. Now the research team believes they have solved the mystery.


Using a computer model of convection in the outer core, together with seismology data, they show that heat flow at the core-mantle boundary varies depending on the structure of the overlying mantle. In some regions, this variation is large enough to force heat from the mantle back into the core, causing localised melting.


Co-author Binod Sreenivasan from the Indian Institute of Technology at Kanpur said: "If Earth's inner core is melting in places, it can make the dynamics near the inner core-outer core boundary more complex than previously thought.


"On the one hand, we have blobs of light material being constantly released from the boundary where pure iron crystallizes. 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.


"Interestingly, not all dynamo models produce heat going into the inner core. So the possibility of inner core melting can also place a powerful constraint on the regime in which the Earth's dynamo operates," he added.


The research will be published in the journal Nature. (ANI)


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