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Gutenberg, Beno

core waves liquid solid

[gootn berg](1889–1960) German–US geophysicist: demonstrated that the Earth’s outer core is liquid.

Gutenberg studied at Darmstadt and at Göttingen before being appointed professor of geophysics at Freiberg in 1926. In 1930 he moved to America to join the California Institute of Technology, becoming director of its seismological laboratory in 1947.

By 1913 it was known that, on the opposite side of the Earth to an earthquake, there is a shadow zone in which compressional P (push–pull, primary) waves arrive later than expected and with reduced amplitude, and in which shear S (shake, secondary) waves are absent; had previously interpreted the delayed arrival of P waves as evidence for the existence of a core. Gutenberg realized that the absence of shear waves meant in addition that the core was liquid. He showed that the boundary between the solid mantle and the liquid core occurs at a depth of 2900 km; this interface is known as the Gutenberg discontinuity. It is now known from the work of that there is an additional solid inner core, at a depth of about 5150 km .

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