Home

Aogashima volcano

Aogashima is a beautiful lonely island, 300km south of Tokyo, and is surrounded by sea cliff. The last eruption is AD1783-1785.
Photographs

Quaternary volcanoes DB in Japan (Aogashima)

Geological map (Takada, 1992, 1994)


Geology of Aogashima Volcano

The edifice volume: about 30 km3 // The relative height from the sea bottom: 1100 m // The highest peak: Otonbu, 423m // The population: a villege of 200 people on the northernwest slope.

The history of Aogashima Volcano (about 3 km3 in volume) (Takada et al., 1992; 1994).
(1) [Pre Main stratocone] The growth of
Kurosaki Volcano (0.3 km3) in the northwestern area of Aogashima island.
(2) [before 3000 y.B.P.] The construction of the main edifice of
Main stratocone in the southeastern area.
(3) [~3,500 y.B.P.] Fissure eruptions of Aphyric basalts (<0.1 km3) on the northwestern flank.
(4) [~3,000 y.B.P.] A surge activity (Ojiroike Surge Deposits) .
(5) [3,000-2,400 y.B.P.] The eruptions of
Kintagaura Lavas (0.15 km3) filling the southeasern basin, and airfalls (Yasundogo Aairfalls Tephras) (0.4 km3) on the east and north flanks.
(6) the occurrence of a debris avalanche (Nagashizaka Debris Avalanche Deposits) associated with the formation of the Ikenosawa Crater (1.7 km x 1.5 km in size).
(7) [A.D. 1781-1785]
the Tenmei eruption (0.08 km3) (an ash fall in 1781; an scoria fall in 1783; intermittent ash falls in 1785; lava flows in the Ikenosawa Crater) (SiO2=61%).

// Aogashima Volcano is composed mainly of tholeiitic basalt (SiO2= 49-63%). During the development of Aogashima volcano, magma paths were shifted over a distance of about 4 km. The chemical composition of magma changed with the shift in magma path. The magma-supply rate of Aogashima volcano was fluctuating in time and space with the growth of each geological unit, which may have led to the generation of andesite magma.


References
The Board of Education and the village office of Aogashima island (1984) The life and culture of Aogashima island. The village office of Aogashima island, 1053 p. (in Japanese).
Isshiki, N. (1955) Ao-ga-sima volcano. Japanese J. Geol. Geogr., 26, 209-218.
Kobayashi, I. (1981) History of Aogashima island. The village office of Aogashima island, 601 p. (in Japanese ).
Omori, F. (1903) Record of the seismic and volcanic disturbances in Hachijo-jima and Ao-ga-shima. Reports Imp. Earthq. Invest. Com., 43, 25-33 (in Japanese with English abstract).
Suga, K. and Fujioka, K. (1990) Volume of volcanic materials along northern Izu-Bonin Arc, Bull. Volcanol. Soc. Japan, 35, 359-374 (in Japanese with English abstract).
Takada, A. (1989a) Aogashima volcano. Bull. Volcanol. Soc. Japan, 34, 177-179 (in Japanese).
Takada, A. and Yuasa, M. (1990) 1:200,000 geological map, Hachijjima. Geol. Survey of Japan.
Takada, A, Oshima, O., Aramaki, S., Ono, K., Yoshida, T., and Kajima, K. (1992) Geology of Aogashima volcano, Izu Islands, Japan. Bull. Volcanol. Soc. Japan, 37, 233-250.
Takada, A, Murakami, and Yuasa, M. (1994) Geological maps of Aogashima volcano and submarine volcanoes, south of Izu Islands, Geological survey of Japan, Geological map of volcanoes 7.
Tokyo-To (1990) Report of studies on the characteristics of volcanic eruptions in the Izu islands area. Committee for Disaster Prevention, Tokyo-to, the booklet of Aogashima. 89 p. (in Japanese).
Tsuya, H. (1937) On the volcanism  of the Huji volcanic zone, with special reference to the geology and petrology of the Izu and southern islands. Bull. Earthq. Res. Inst., 15, 215-357.