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
Geology of Ascension Island same time as the Sister's Peak region 829,000 years ago. Bentmoreite scoria cones record evidence of mafic volcanism, although older rhyolite and trachye flows, domes and pyroclastic deposits point to felsic eruptions as well. The Central Felsic Complex (CFC), centers on Green Mountain and Middleton Ridge and is older than the Eastern Felsic Complex. Here, ash is typically welded together and breccia is laden with rhyolite and obsidian fragments. Middleton Ridge formed more than one million years ago and is accompanied trachyte and rhyolite flows. By comparison, Green Mountain formed as recently as 395,000 years ago with trachyte flows and