Oceanic plateau
From Wikipedia, the free encyclopedia
An oceanic plateau (also submarine plateau) is an undersea large igneous province, the equivalent of continental flood basalts such as the Deccan Traps in India and the Snake River Plain in the Pacific Northwest of the United States. An oceanic plateau, as its name suggests, rises above the level of the ambient seabed.
Geologists believe that oceanic plateaus may well represent a stage in the development of continental crust as they are generally less dense than oceanic crust while still being more dense than normal continental crust.
Density differences in crustal material largely arise from different ratios of various elements, especially silicon. Continental crust has the highest amount of silicon and is called "felsic". Oceanic crust has a smaller amount and is called "mafic". Oceanic plateaus have a ratio intermediate between continental and oceanic crust, although they are more mafic than felsic.
However, when a plate carrying an oceanic plateau subducts a plate carrying oceanic crust, the volcanism which erupts on the plateau as the oceanic crust heats up on its descent into the mantle erupts material which is more felsic than the material which makes up the plateau. This represents a step toward creating crust which is increasingly continental in character, less dense and more buoyant. If an oceanic plateau is subducted underneath another one, or under existing continental crust, the eruptions produced thereby produce material that is yet more felsic, and so on through geologic time.
[edit] List of oceanic plateaus
Kerguelen Plateau (Indian Ocean)
Ontong Java Plateau (South Pacific)
Caribbean-Colombian Plateau (Caribbean)
Central Atlantic Magmatic Province (North Atlantic)
Shatsky Rise (North Pacific)
Agulhas Plateau (South Atlantic)
Marion Plateau
