Unzen, Again

I did some extensive rewriting of the original post on the Decade Volcano for the upcoming eBook and also included an intriguing video of a train trip around the peninsula. What do you think?

Japan’s Unzen Volcano is a complex of lava domes and low stratovolcanoes, none of them more than 5,000 feet high.

It’s big enough to cover most of the Shimabara Peninsula, which sits across an inlet of the East China Sea east of Nagasaki (yes, that Nagasaki).

Unzen is one of the few Decade Volcanoes that killed people during the 1990s.

Chances are that you only know it from an online video showing a huge pyroclastic flow that surges over a ridge as people in the foreground flee in terror.

And that did happen at Unzen in June 1991.

While those we see in this video lived, the fiery gray cloud of pulverized rock and searing gases coming at them had just killed 43 people, including volcanologists Harry Glicken and Maurice and Katia Krafft.

Glicken was a pioneer in volcanic avalanche studies.

The Kraffts filmed erupting volcanoes. They were at Unzen that day to obtain more footage for a public education film about volcano hazards. (Thompson)


One reason why experts made Unzen a Decade Volcano is that Shimabara City and other large population centers are only a few miles away.

And Japan’s worst recorded volcanic disaster happened here in 1792.

That’s when eruption seismicity triggered the partial collapse of one of Unzen’s largest lava domes.

The landslide debris missed the famous castle and its samurai but cascaded through what’s now Shimabara City and smashed into the sea, causing a 180-foot-high tsunami.

About 15,000 people died that day.

Once the International Decade got underway, Unzen also attracted much scientific attention.

It awoke from a two-century sleep in 1990 and then surprised volcanologists by extruding from its summit lots of sticky gray lava, which accumulated atop Mount Fugendake –the current center of Unzen’s activity — as a large dome.

This was very unstable, of course, and frequently collapsed in pyroclastic flows, including the lethal one on June 3, 1991.

It’s important to point out that there were triumphs for the Decade Volcano program here, as well as tragedy.

This was one of the first eruptions monitored in-depth by volcanologists from start to finish.

Unzen was so well “wired” that they were able to accurately predict the time and location when lava first appeared.

While nothing could be done at the time to prevent the $2 billion in property damage, experts and emergency managers issued life-saving warnings multiple times and successfully evacuated people before a pyroclastic flow occurred. (Nakada and Eichelberger; Newhall)

As a measure of their success, only one other fatality is listed after the Krafft/Glicken group: someone who ventured into an evacuation zone in 1993 and was caught by a pyroclastic flow. (Brown et al.)

But not all is death and destruction at Unzen.

As always, people are drawn here by the scenery and the volcano’s many direct and indirect benefits.

Vacation video:

First, here is a quick overflight:

Video note: This gorgeous region was Japan’s first national park. Today it is also a UNESCO Geopark.

Now, if you like, you can venture out on a forty-minute self-explanatory excursion around the Shimabara Peninsula on a cute little yellow train.

This presentation focuses on the people and on tourist attractions. They only mention Unzen a few times, but it is always there, nevertheless.


32.761° N, 130.299° E, in Nagasaki Prefecture, northwest Kyushu, Japan. The GVP Volcano Number is 282100.

Nearby Population:

Per the Global Volcanism Program website:

  • Within 5 km (3 miles): 6,979.
  • Within 10 km (6 miles): 76,424.
  • Within 30 km (19 miles): 444,737.
  • Within 100 km (62 miles): 7,313,362.

Current Status:

Aviation Code Green, normal.


  • Eruption styles: Explosions, lava flows, pyroclastic flows, debris flows, and lahars (ashy mud flows).
  • Biggest recorded event: The Mayuyama dome collapse in 1792.
  • Most recent eruption: 1996.
  • Past history: Volcanic activity may have started on the southern part of the peninsula 4 million years ago, eventually reaching its present center around one of the Unzen stratovolcanoes (Mount Fugen, or Fugendake) some 500,000 years ago.

    When you check the GVP’s history, though, the lack of high-VEI eruptions may surprise you.

    Volcanoes, especially those like Unzen that are steep and “crumbly,” don’t have to erupt intensely to be terrible.

    The lethal and costly 1990-1995 eruption was “only” VEI 1 and Unzen’s most recent activity in 1996 was VEI 2, as was the 1792 eruption in which so many thousands of people lost their lives.


The Japan Meteorological Agency (JMA) and the Shimabara Earthquake and Volcano Observatory (Japanese).

Webcam (JMA).

Tokyo Volcanic Ash Center (VAAC) issues aviation advisories as needed.

Featured image: Traction/Shutterstock

Brown, S.K.; Jenkins, S.F.; Sparks, R.S.J.; Odbert, H.; and Auker, M. R. 2017. Volcanic fatalities database: analysis of volcanic threat with distance and victim classification. Journal of Applied Volcanology, 6: 15.

Geological Survey of Japan, AIST. n.d. Active Volcanoes of Japan: Unzen Volcano. https://gbank.gsj.jp/volcano/Act_Vol/unzen/text/eng/exp08-1e.html Last accessed bbn April 2, 2020.

Kyushu University. 1998. Internet Museum: Eruption of Unzen Volcano and its Background. http://museum.sci.kyushu-u.ac.jp/e/

Nakada, S., and Eichelberger, J. 2004. Looking into a volcano: Drilling Unzen. https://www.geotimes.org/mar04/feature_Unzen.html

Newhall, C. 1996. IAVCEI/International Council of Scientific Union’s Decade Volcano projects: Reducing volcanic disaster. status report. US Geological Survey, Washington, DC. Retrieved from https://web.archive.org/web/20041115133227/http://www.iavcei.org/decade.htm

Oregon State University page on the Kraffts. http://volcano.oregonstate.edu/who-were-maurice-and-katia-krafft-how-did-they-die

Oregon State University: Volcano World. 2020. Unzen. http://volcano.oregonstate.edu/unzen

Thompson, D. 2002. Volcano Cowboys: The Rocky Evolution of a Dangerous Science. St. Martin’s Griffin (this edition: https://www.goodreads.com/en/book/show/178244.Volcano_Cowboys)

University of Tokyo Volcano Research Center and Kyushu University Shimabara Earthquake and Volcano Observatory. 1999. Welcome to Unzen Decade Volcano. https://web.archive.org/web/20060615204125/http://hakone.eri.u-tokyo.ac.jp/unzen/index.html

Unzen Tourist Association. n.d. tp://www.unzen.org/e_ver/ Last acessed April 2, 2020.

Wikipedia. 2020. Mount Unzen. https://en.wikipedia.org/wiki/Mount_Unzen Last accessed April 2, 2020.

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