How do seismic waves show that the core of the Earth is mostly liquid?

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   Jupiter on February 19, 2010 at 7:01 pm

   Scientists know there is a mantle and a core, not because of lava, but because of the way earthquake energy passes through the Earth. When an earthquake occurs – like the one in Kobe, Japan recently – waves of energy move in all directions away from the place where the Earth’s rocks broke. The speed that the waves travel depends on the type and temperature of the rocks they pass through. By timing how long waves of different sizes take to travel from the earthquake seismometers around the world, scientists can begin to understand the nature of the rocks buried deep within the Earth.

   There are two important types of earthquake waves: compression waves and shear waves . Compression waves pass through rock and liquids, but shear waves can’t pass through liquids. Seismologists long ago discovered that shear waves do not pass through the central regions of the Earth; therefore, the core of the Earth must be liquid!