GEOS1001 Chapter Notes - Chapter 17: Seismic Refraction, Seismic Wave, Ultramafic Rock
27 Oct 2018
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Document Summary
The interior of the earth is studied indirectly by geophysics a study of seismic waves, gravity, earth magnetism, and earth heat. Seismic reflection and seismic refraction can indicate the presence of boundaries between rock layers. The earth is divided into three major units, the crust, the mantle, and the core. The earth"s (cid:272)rust (cid:271)e(cid:374)eath o(cid:272)ea(cid:374)s is 7 kilometers thick and made of basalt. Continental crust is 30-50 kilometers thick and made of rock that has the same seismic velocity as granite. The mohorovicic discontinuity separates the crust from the mantle. The mantle is a layer of solid rock 2900 kilometers thick and is probably composed of an ultramafic rock such as peridotite. Seismic waves show the mantle has a structure of concentric shells, perhaps caused by pressure transformations of minerals. The lithosphere, which forms plates, is made up of brittle crust and upper mantle. 70 to 125 kilometers thick and moves over the plastic asthenosphere.
