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 primary purpose of The Clay Minerals Society is to stimulate research and to disseminate information relating to all aspects of clay science and technology. Through its conferences and publications, the Society offers individuals a means of following the many-sided growth of the clay sciences and of meeting fellow scientists with widely different backgrounds and interests. The primary activities of The Clay Minerals Society consist of publication of the bi-monthly journal "Clays and Clay Minerals", organization of the annual conference, workshop, and field trip, student research grants, publication of a workshop lecture series, slide sets, and special publications, the providing