View of Mt. Mayuyama is toward the north. Mt. Mayuyama is one of the dacite lava domes that form the Unzen Volcano complex on Kyushu Island, Japan. The east flank of Mt. Mayuyama collapsed without warning on May 21, 1792, and generated a landslide that swept through Shimabara City and slammed into the Ariaka Sea. The displacement of water triggered a tsunami along the adjacent shoreline of Shimabara Peninsula (visible above and right of Mayuyama) and also 17-23 km across the Ariaka Sea in neighboring provinces. The landslide and tsunami killed nearly 15,000 people, Japan's worst historical volcanic disaster.
Scientists have interpreted the conspicuous hummocks along the shore as part of a landslide deposit that occurred before 1792. Maps submitted to the Tokugawa Shogunate in 1792 as the official documents of the Shimabara Catastrophe clearly show the existence of small islands before the disaster struck.
Other historical volcano landslides are known to have generated tsunami, including:
Siebert, L., 1984, Large volcanic debris avalanches: characteristics of source areas, deposits, and associated eruptions: Journal of Volcanology and Geothermal Research, v. 22, n. 3/4, pp. 163-197.
Miyachi, M., 1992, Geological examination of the two old maps from the Tokugawa Era concerning the Shimabara Catastrophe: in Yanagi, T., Okada, H., and Ohta, K. (eds.), Unzen Volcano, the 1990-1992 eruption, Nishinippon & Kyushu University Press, pp. 99-102.
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