Structure of the Earth 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
Sulfate crust into the atmosphere. Sulfate crust Sulfate crust is a zone observed in the axial (central) parts of burning coal dumps and related sites. It is a zone built mainly by anhydrous sulfate minerals, such as godovikovite and millosevichite. The outer zone can easily be hydrated giving rise to minerals like tschermigite and alunogen. The zone forms due to interaction with hot (even around 600 °C) coal-derived gases (mainly NH and SO) with the "sterile" material (i.e. shales and other rocks serving as the source of Al, Fe, Ca and other cations) in case of the lack of vents for the