磐梯山明治噴火による地形
文献にもとづく問題の整理
1971 年 23 巻 1 号 p. 10-17
詳細
1971 年 23 巻 1 号 p. 10-17
Based on the various literatures and some field data relating to the geomorphology of Bandai-san which erupted in the 21st year of Meiji (1888), the author concludes as follows;
(1) The applciation of the term “directed vocalnic blast” to the Meiji eruption by G. S. Gorshkov (1959, 1963) is justified with the exmaination of the details of the accident including the damage on people and trees etc. It must be noted, however, that S. Sekiya and Y. Kikuchi (1890) on which Gorshkov's applciation depends had used the term “wind blast” and described the nature of blast transmission and the related phenomena. Gorshkov expresses that the property of the eruption has not been fully understood and claims the applcaition of the term mentioned above. But the present author can not state positively so.
(2) Two mudflows were poured out at that eruption, namely Ura-bandai Mudflow to the north and Biwa-saw Mudflow to the southeast. G. S. Gorshkov applied his term “agglomerate flow” to both mudflows. The present author disagrees with him. The materials of Ura-bandai Mudflow is not sutiable to be named “agglomerate” viewed from the rule of lithological nomenclature, as pointed out by Prof. Toshio Ishikawa (1970 pers. communciation). Biwa-sawa Mudflow is composed chiefly of the red loamy soil underlain the contemporary mountain slope.
(3) It is questionable whether the materials of Ura-bandai Mudflow was saturated with water or not and some Japanese and foreign textbooks write that the materials contain much water. The descriptions on the ground conditions just after the accident set by Sekiya & Kikuchi (1890) who began their field study four days after the eruption and Prof. Hatsuo Yasuda (1949) who checked the official record at that time-said that the mudflow was dry.
(4) On the geomorphology of Ura-bandai Mudflow, some questions have been unsolved. The first of them is the forming process of flow mounds. Various field data and various theories were proposed, but no reasonable conclusion is found by the author. He thinks that it is necessary to make a systematic data smapling on the topography and geology of b-area and c-area (Fig. 3) respectively.
(5) On the whole, what is necessary for the geomorphology around Bandai-san are not new terms but much field data.
