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
The Clay Minerals Society The Clay Minerals Society The Clay Minerals Society is an international non-profit organization devoted to the study of clays and clay minerals. The Clay Minerals Society began as the Clay Minerals Committee of the National Academy of Sciences—National Research Council in 1952, in response to the need for a formal way to hold national clay conferences. By 1962, the Clay Minerals Committee had become strong enough to stand on its own, and The Clay Minerals Society was incorporated. From 1952 to 1964, Proceedings of the annual conferences were published. The journal Clays and Clay Minerals was first published in 1964.