著者

荒牧 重雄

出版者

特定非営利活動法人日本火山学会

雑誌

火山. 第2集 (ISSN:04534360)

巻号頁・発行日

vol.32, no.1, pp.57-72, 1987-04-30

被引用文献数

3

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Lake Nyos is a maar-type volcano formed by phreatomagmatic eruption along the fissure. The rock is weakly alkaline olivine basalt very rich in crustal xenoliths and mantle-derived spinel-lehrzolite nodules. Stratiied surge deposits made of scoria and ash drape the pre-Cambrian(?) granitic basement along the lake shore. Lake Nyos is a part of Cameroon Volcanic Line which contains many fields of monogenetic volcanoes. Among them is another maar-type crater lake Monoun, which erupted similar lethal gas(CO_2) in 1984 and killed 37 people. The rocks of these young monogenetic volcanoes range from weakly to strongly alkaline basalts and basanitoids. The older(Tertiary?), plateau-forming basalts which constitute immediate basement are also alkaline basalts and basanitoids.