IntroductionIchinomegata, the easternmost, largest, and oldest of the three maars, is 600 m in diameter. Ninomegata and Sannomegata are located immediately east and south of Toga Bay (Togowan), which itself is a maar. The rim of the rhyolitic Toga (Togowan) maar, larger than the Megata maars, is breached by the sea on the western side and was formed about 450,000 years ago. The Megata maars are mostly late Pleistocene in age, but Murayama (1987) noted that pottery from roughly 4000 years before present has been found within tephra layers from the maars.
- Smithsonian GVP volcano information
- Murayama I, (1987) "Volcanoes of Japan (I)", Tokyo: Daimedo, 315 p (2nd edition, in Japanese)
- Katsui et al (1979) "GENESIS OF CALC-ALKALIC ANDESITES FROM OSHIMA-OSHIMA AND ICHINOMEGATA VOLCANOES, NORTH JAPAN", J. Fac.Sci., Hokkaido Univ., Series IV, v. 19 (1-2), pp. 157-168
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