Study Discusses Causes and Risks of Catastrophic Caldera-forming Eruptions

Text and figures for this press release are downloadable from the link below.

• Press Release Kit

Professor TATSUMI Yoshiyuki and Associate Professor SUZUKI Keiko from the Department of Earth and Planetary Sciences at Kobe University’s Graduate School of Science statistically analyzed the scale and frequency of volcanic eruptions that have occurred in the Japanese Archipelago in the past 120,000 years and have obtained important new findings. These findings were publicly released to the media, including the Ministry of Education, Culture, Sports, Science and Technology (MEXT) Press Club, on October 22, 2014.

1. Normal eruptions and catastrophic caldera-forming eruptions occur due to different mechanisms relating to magma composition and eruptive style. It is suggested that large magma reservoirs, which cause catastrophic caldera-forming eruptions, lead to eruptions when cracks are caused by their melt buoyancy.
2. Volcanoes prone to catastrophic eruptions are located in regions with a low crustal strain rate. The study proposed that viscous silicic melts that cause such eruptions can be readily segregated from the partially molten lower crust, forming a large magma reservoir in such a tectonic regime.
3. There is an approximately 1% probability of a catastrophic eruption in the next 100 years in the Japanese Archipelago. This is the same level as that of the 30-year probability immediately before the 1995 Kobe Earthquake struck Japan. Therefore, it should be recognized that such catastrophic eruptions can be triggered at anytime. In the worst case scenario, more than 120 million people are anticipated to be unable to sustain their lives^(*) in the aftermath of such a catastrophic caldera-forming eruption.

These research findings will be published in Proceedings of Japan Academy, Series B, Physical and Biological Sciences on November 11, 2014. (Edited: It is published at http://www.japan-acad.go.jp/en/publishing/pja_b/contents/90/90_9.html)

(*) Edited on November 6, 2014:

The original press release kit showed a 120 million death toll since substantially 120 million fatalities were anticipated. However, during the press conference, an inconsistency with the paper published on the Proceedings of Japan Academy, Series B, Physical and Biological Sciences was pointed out and the expression was revised to read as follows: 120 million people are anticipated to be unable to sustain their lives.

(Graduate School of Science Faculty of Science)