Hachimantai volcanHachimantai (Hatimantai) volcano is a complex stratovolcano in northern Honshu, Japan, located at the front of the northern Honshu volcanic arc. It belongs to the Towada-Hachimantai National Park.
Hachimantai was originally the name of a small peak (1614m) in the northern Sengan area, but is now commonly used as the name for the entire volcanic group, which contains several cones and craters in a widely scattered area.
Its summit is a vast undulated plateau containing circular craters near Komono-more and Mokko-dake in the center.
There are no historical eruptions from the volcanic group and the last activity is probably more than 7000 years ago, but there are still major major gas emissions around the Fukenoyu cone and active solfataras are found on the western and southern flanks.
Introduction:Hachimantai was built from from widely scattered vents during the Pleistocene and is capped with andesitic lavas from vents in the center of the complex.
The Hachimantai volcanic group comprises the Chausudake-Maemoriyama, Ofukadake-Magarizakiyama and the Hachimantai-Morobidake group, which itself consists of several vents and volcanic edifices: 2 major andesitic cones of Hachimantai and Chausu-dake, and 2 major basaltic cones, Fukenoyu and Morobi-dake, as well as several minor dacitic, andesitic, and basaltic cones including Komono-morem, Mokko-dake, Ebisumori, Daikokumori, Yanomune-dake, Appi-dake.
Hachimantai is similar to the Iwate volcanic field in vent alignment and rock type, including high magnesium andesites, likely produced by 2-stage magma mixing. Both contain sub-parallel W-E trending volcanic chains at a spacing of about 12 km. In both volcanic chains, andesite cones are situated at the western end, and basalt to basaltic andesite magmas are erupted in the middle and eastern chains.
Volcanic activity at Hachimantai occurred in at least 3 major periods:
1) 0,7-1 million years ago (mainly andesites),
2) 300-400,000 years ago (basalt, high-magnesian andesite, andesite and dacite magmas).
3) 100-200,000 years ago (basalt magmas).
- Smithsonian / GVP volcano information
- Quaternary Volcanoes of Japan. Geol Surv Japan, AIST
- Ohba et al (2007) "High-Magnesian Andesite Produced by Two-Stage Magma Mixing: a Case Study from Hachimantai, Northern Honshu, Japan", J. Petrology, v. 48(3), pp 627-645
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