"The Abu volcano group, located along the Japan Sea coast near the SW end of Honshu, consists of basaltic-to-dacitic lava flows, small shield volcanoes (some of which have associated cinder cones) and lava domes. More than 40 monogenetic volcanoes are located in an area of 400 sq km. Irao-yama at 641 m forms the high point of this group of small volcanic edifices, some of which form offshore islands or submarine vents. Volcanism here is considered to be related to subduction of the Philippine Sea Plate. An earlier phase of activity at the dominantly Pleistocene Abu volcano group during the late-Pliocene to early Pleistocene was followed by renewed activity about 800,000 years ago that continued into the Holocene. The latest dated eruption was dated by thermoluminescence at about 8800 years ago."  -Smithsonian Volcano Archive
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