Lecture 25-26 Earth's Structure(1)

L hugo benio in 1940 mapped out the locahon of deep

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Unformatted text preview: 0 31 l༆  Now it is reasonable to ask, first of all, “How do we know that the Earth’s core is solid ?” and “Why is it solid when the outer core is liquid?” l༆  First evidence of a solid core came from travel Hme of P- waves, through the Earth, on more sensiHve seismographs developed in the 1930s. l༆  If you assume a low velocity core, because it is all liquid, then you expect a certain travel Hme for p- waves that go through the Earth’s core. l༆  More sensiHve seismographs detected a faster than expected arrival Hme 32 33 l༆  The conclusion was that the central core must be a high velocity region. l༆  ImplicaHon is that it must be solid. l༆  That is what it is, a solid, extremely hot, iron- nickel alloy. l༆  March 1964 Anchorage, AK Earthquake and presence of seismometers around the Earth confirmed the theory Crust ComposiHon 34 l༆  ConHnental Crust and Oceanic Crust are made of different materials l༆  ConHnental crust is mostly granite (density approximately 2700 kgm- 3 l༆  Oceanic crust is mostly basalt (density approx. 2900 kgm- 3) Crust ComposiHon 35 l༆  Lithosphere...
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This document was uploaded on 01/17/2014.

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