2. The Outline of the 1970-71 Eruption of Akita-Komagatake(IV. Chronorogy of the 1970-71 Eruption of Akita-Komagatake)

Abstract

The writers intend here to sketch in broad outline the 1970-71 mixed eruption of Akita-Komagatake with special reference to explosion earthquakes. This is the first magmatic eruption of the volcano in the historical time. The present eruption took place near the summit of Medake, one of the central cones of the composite volcano, on September 18, 1970, after a long repose of 38 years, and continued without interruption until January 26, 1971. The total of the new volcanic products was ca. 4×10⁶ tons (lava : ca. 3.34×10⁶ tons, ejecta : ca. 0.67×10⁶ tons). The total kinetic and thermal energies estimated by solid products were ca. 1.6×10²⁰ ergs and ca. 5.0×10²² ergs, respectively.