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
Magnesite in Greece Magnesite in Greece Magnesium (Mg) is a chemical element, an alkaline earth metal, the eighth-most abundant element in the Earth's crust and the fourth-most common element on Earth. It is contained in magnesite, dolomite, brucite, carnallite, talc, and magnesium minerals. China is now the biggest producer of crude magnesite in the world for refractory and agricultural uses. Crude magnesite was produced in Greece in 1910. It was first found in Atalanti and in the Province of Lokris, central Greece. Other localities were Perachori, near Corinth; Ermioni (or Kastri) and on Spetses Island in southern Argolis in the Peloponnese; on Paros