The ________ forms the relatively cool. brittle plates of plate tectonics.

53) The forms the relatively cool, brittle plates of plate tectonics. A) Asthenosphere B) Lithosphere C) Astrosphere D) Hydrosphere rocks form by crystallization of magma. 54) A) Sedimentary B) Indigenous C) Primary D) Igneous


53) lithosphere Lithosphere, Rigid, rocky outer layer of the Earth, consisting of the crust and the solid outermost layer of the upper mantle. It extends to a depth of about 60 mi (100 km). It is broken into about a dozen separate, rigid blocks, or plates. Slow convection currents deep within the mantle, generated by radioactive heating of the interior, are believed to cause the lateral movements of the plates (and the continents that rest on top of them) at a rate of several inches per year. 54) Igneous

igneous rocks form from when hot, molten rock crystallizes and solidifies. The melt originates deep within the Earth near active plate boundaries or hot spots, then rises toward the surface. Igneous rocks are divided into two groups, intrusive or extrusive, depending upon where the molten rock solidifies.

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