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
Potassium studies because potassium is a macronutrient required for life. Potassium is formed in supernovae by nucleosynthesis from lighter atoms. Potassium is principally created in Type II supernovae via an explosive oxygen-burning process. is also formed in s-process nucleosynthesis and the neon burning process. Potassium is the 20th most abundant element in the solar system and the 17th most abundant element by weight in the earth. It makes up about 2.6% of the weight of the earth's crust and is the seventh most abundant element in the crust. The potassium concentration in seawater is 0.39 g/L (0.039 wt/v%), about one twenty-seventh