lithosphere [%PREMIUM_LINK%] (lĭth'ə-sfîr') Pronunciation Key |
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The outer part of the Earth, consisting of the crust and upper mantle. It is about 55 km (34 mi) thick beneath the oceans and up to about 200 km (124 mi) thick beneath the continents. The high velocity with which seismic waves propagate through the lithosphere suggests that it is completely solid. Compare asthenosphere, atmosphere, hydrosphere.