Mount Unzen has been dubbed as the most lethal of all volcanoes in Japan. It is an active volcano located on the island of Kyushu, near the city of Shimabara, Nagasaki Prefecture. It has been recorded having several violent eruptions with many casualties. However, the place is also a popular destination for tourists due to the hot springs on its southwest side.
Since prehistoric times, Shimabara Peninsula was seen to be an area of extensive volcanism for many years. Unzen complex was formed from eruptions of dacitic lava. In 200,000 years, the volcano grew rapidly which ultimately formed a large cone. As a product if its activity, the complex formed four domes at different sites: No-dake, Myoken-dake, Fugen-dake, and Mayu-yama volcanic peaks. Fugen-dake is its highest peak (1,359 meters).
The mountain’s deadliest eruption occurred in 1792 on the night of May 21 which caused an earthquake and tsunami in the area. One side of the mountain (Mayuyama dome) collapsed which swept through the city and into Ariake Bay. It resulted in a tremendous tsunami killing 15,000 inhabitants. The tsunami was considered to be a megatsunami due to its huge waves reaching a height of 100 meters. It first struck the Higo Province and bounced back hitting Shimabara. It is said that 5,000 people were killed by the landslide, 5,000 by the tsunami in Higo Province and another 5,000 by the tsunami in Shimabara.
Unzen calmed down for several years after that but in 1990 it erupted again and was followed by many intermittent eruptions. In 1991, a group of journalists and scientists ventured into the danger zone when the mountain violently erupted again killing them all. The latest eruption is said to have ended in 1995.
Unzen is now considered a part of Unzen-Amakusa National Park. It has now become a popular destination due to its hot spring resorts. During hot summers in Japan, it remains cool. Around 30 hot springs are available in the area where you can bath as a couple at a cheap price of 100 yen at a time.
With such violent history, Mount Unzen is no doubt Japan’s deadliest mountain. If you are planning on visiting, you can take a bus from Isahaya Station in the Nagasaki Prefecture which will take you to Unzen Koen Park and usually takes around an hour and fifteen minutes. You may also take the ferry boat from Kumamoto Port to Shimabara.