Magma plumbing system beneath Chokai volcano

2016 Fiscal Year Final Research Report

• Project/Area Number: 26400509
• Research Category: Grant-in-Aid for Scientific Research (C)
• Allocation Type: Multi-year Fund
• Section: 一般
• Research Field: Petrology/Mineralogy/Economic geology
• Research Institution: Yamagata University
• Principal Investigator: Ban Masao 山形大学, 理学部, 教授 (50208724)
• Project Period (FY): 2014-04-01 – 2017-03-31
• Keywords: 活火山 / マグマ供給系 / 噴火史 / 鳥海山 / 東北日本 / 噴火のタイムスケール / 東北地方太平洋沖地震 / 東鳥海カルデラ

Outline of Final Research Achievements

Chokai volcano is a Quaternary stratovolcano in NE Japan. The newest collapse was at BC466 and a caldera was formed. Effusion of lavas in this caldera has continued intermittently to present. This volcano erupted (Jougan eruption) after the Jougan big earthquake. Thus, after 2011 Tohoku earthquake, it is important to examine the geologic and petrologic features around Jougan eruption to predict future eruption.
Detailed volcano stratigraphic analysis reveald that the eruption rate decreased and the compositions of mafic magma were changed after the Jougan earthquake. By the petrologic investigations revealed followings. The magma plumbing system is composed of shallow chamber filled by lower temperature magma which was repeatedly infused by mafic magmas from depths, which resulted in the eruptions. The time scales from the infusions to th eruptions are estimated to be less than several years. The compositions of the mafic magma changed at the timing of the Jogan earthquake.

Free Research Field

岩石学、火山学