1792 Unzen Eruption and Tsunami

Background. Mount Unzen is an active stratovolcano near Shimabara on Kyūshū. In late 1791, earthquakes on the western flank moved toward Fugen-dake. Eruptions began in February 1792, producing a lava flow that lasted two months. These events preceded the catastrophic collapse of the Mayuyama dome, which triggered the deadly landslide and tsunami.

Disaster. On May 21, 1792, earthquakes caused the collapse of the Mayuyama lava dome. The resulting landslide swept through Shimabara and into the Ariake Sea, generating a tsunami. The disaster killed approximately 15,000 people, making it Japan's worst volcanic-related disaster. It was known as 'Shimabara suffered, Higo affected' due to casualties in both regions.

Casualties. Of the estimated 15,000 fatalities, around 5,000 died from the landslide in Shimabara. Another 5,000 perished from the tsunami in Higo Province, across the Ariake Sea. A further 5,000 were killed when the tsunami returned to strike Shimabara. This event remains the largest scale volcanic disaster in Japanese history.