Ōjin Seamount (応神海山) is an underwater volcano classified as a seamount within the Hawaiian–Emperor seamount chain of the Pacific Ocean. It is considered an extinct volcanic structure.
Geology and form
Ōjin has a characteristically flat summit and is therefore described as a guyot. Such flat-topped seamounts commonly were planed off by wave action when they stood near or above sea level; subsequent cooling and the weight of the oceanic crust caused the volcanic edifice to subside to its present depth.
Like other members of the Hawaiian–Emperor chain, Ōjin was produced as the Pacific Plate moved over a volcanic hotspot. Geological evidence indicates the last volcanic activity at Ōjin occurred roughly 55 million years ago, and no eruptions have taken place since, classifying it as extinct.
Name
The seamount is named for the historical Japanese ruler Emperor Ōjin.