basalt is the most common type of rock in earth's crust.
basalt is the most common type of rock in earth's crust.
the most common type of rock in earth's crust is?
basalt
the earth's crust ranges from in depth and is the outermost layer. the thin parts are the oceanic crust, which underlie the ocean basins (5–10 km) and are composed of dense (mafic) iron magnesium silicate igneous rocks, like basalt. the thicker crust is continental crust, which is less dense and composed of (felsic) sodium potassium aluminium silicate rocks, like granite. the rocks of the crust fall into two major categories – sial and sima (suess, 1831–1914). it is estimated that sima starts about 11 km below the conrad discontinuity (a second order discontinuity). the uppermost mantle together with the crust constitutes the lithosphere. the crust-mantle boundary occurs as two physically different events. first, there is a discontinuity in the seismic velocity, which is most commonly known as the mohorovičić discontinuity or moho. the cause of the moho is thought to be a change in rock composition from rocks containing plagioclase feldspar (above) to rocks that contain no feldspars (below). second, in oceanic crust, there is a chemical discontinuity between ultramafic cumulates and tectonized harzburgites, which has been observed from deep parts of the oceanic crust that have been obducted onto the continental crust and preserved as ophiolite sequences.
structure of the earth
section::::types of crust.:secondary crust.









































secondary crust is formed by partial melting of silicate materials in the mantle, and so is usually basaltic in composition.









































this is the most common type of crust in the solar system. most of the surfaces of mercury, venus, earth, and mars comprise secondary crust, as do the lunar maria. on earth, we see secondary crust forming primarily at mid-ocean spreading centers, where the adiabatic rise of mantle causes partial melting. 









































section::::types of crust.:tertiary crust.









































tertiary crust is more chemically-modified than either primary or secondary. it can form in several ways:
crust (geology)