Volcanic plateau up by foundering of the Earth's crust to form the present ocean basin. The Earth features numerous subaerial and submarine volcanic plateaus such as the Columbia River Plateau (subaerial) and the vast Ontong Java Plateau (submarine). Pyroclastic plateaus are produced by massive pyroclastic flows and they are underlain by pyroclastic rocks: agglomerates, tephra, volcanic ashes cemented into tuffs, mafic or felsic. Examples include Shirasu-Daichi which covers almost all of Southern Kyūshū, Japan and the North Island Volcanic Plateau in New Zealand. Volcanic plateau A volcanic plateau is a plateau produced by volcanic activity. There are two main types: lava plateaus
Charnockite thoroughly reconstituted clays and shales. It is of wide distribution and great importance in India, Ceylon, Madagascar and Africa. It was named by geologist T. H. Holland in 1893 after the tombstone of Job Charnock, in St John's Church in Calcutta, India, which is made of this rock. The charnockite series includes rocks of many different types, some being felsic and rich in quartz and microcline, others mafic and full of pyroxene and olivine, while there are also intermediate varieties corresponding mineralogically to norites, quartz-norites and diorites. A special feature, recurring in many members of the group, is the presence