1974年1月13日の時点における西之島新島から大気への放熱量の推測

抄録

Since April 1973 a volcanic activity which brought forth a new volcanic island has been observed near 27°14.5´N and 140°53´E on the east of the Island of Nishinoshima, the Ogasawara Islands, about 930 km south of Tokyo. 0n 13 January 1974 which falled on between December 1973 when the newly-formed island was named formally the Island of Nishinoshima-Shinto and June 1974 when the new island began to connect with the Island of Nishinoshima, surface temperatures of both islands and their peripherical sea were measured at the flight levels from 300 to 900 m with the airborne infrared line scanner Model DEI-1200 (Kubotera, Tanaka and Ossaka, 1974). The distribution of surface temperatures and other information concerning with the eastern pit of the Island of Nishinoshima-Shinto observed with the eye from the aircraft were utilized to estimate heat discharge from the Island of Nishinoshima-Shinto, based on a method developed by Yuhara and Sekioka (1975) to assess heat discharge from the summit crater of Miharayama volcano. Estimation shows that total radiant flux from the eastern pit and heat discharge from the Island of Nishimshima-Shinto excluding the eastern pit were 7.4×10⁶ cal/sec and 2.0×10⁷ cal/sec, respectively. Furthermore, radiant flux from flying volcanic bombs spouting from the eastern pit was computed 5.3×10² cal/sec which is negligible amount. Total heat discharge was then of 2.7×10⁷ cal/sec. Comparing this value with the other estimated one of 3.3×10⁶ cal/sec at July 1975, about one and half years later, by Ehara and Yuhara (1975), cooling of the Island of Nishinoshima-Shinto seems to be suggested.