The Yomiuri ShimbunIt has been two months since 12 people were killed or injured in the eruption of Mt. Motoshirane, which is part of Mt. Kusatsushirane in Gunma Prefecture. Volcanoes that regularly emit smoke are worrying, but we must not forget about the volcanoes that seem quiet, either. Could other volcanoes also suddenly erupt right before tourists’ eyes like Mt. Motoshirane? What countermeasures are needed? The Yomiuri Shimbun asked a professor at the University of Toyama, Yasuo Ishizaki, a volcanologist who has studied Mt. Motoshirane.
The following is an excerpt from the interview.
Lack of vigilance
The Yomiuri Shimbun: Observation equipment to predict eruptions was not installed at Mt. Motoshirane. Why?
Yasuo Ishizaki: The most lively volcanic activities in the Mt. Kusatsushirane area had been seen around Yugama on Mt. Shirane, where the detection equipment was concentrated. I started a geological survey on Mt. Motoshirane in 2013 and found that a magma eruption occurred around 1,500 years ago. I have spoken about this several times at society meetings, and also was just compiling a new paper, warning that it was not enough to merely look at Mt. Shirane. I was too late.
Q: Why were you studying Mt. Motoshirane even though it had no historical record of eruptions?
A: I just happened to visit the site in 2012 and found around 50 centimeter in diameter volcanic stones thrown out by the volcano lying on the side of the trail. It was originally thought that the last eruption was around 3,000 years ago, but I had a feeling it was more recent. Since then, I have been studying the geological strata with other researchers. You have to keep visiting a mountain for years before you finally start to see its eruption history.
But small-scale water vapor eruptions like the one in January don’t leave any marks in the strata, and there is no way to tell how frequently they have occurred in the past. Countless small eruptions have probably occurred between eruptions large enough to leave indications of activity in the strata.
Q: Besides Mt. Motoshirane, many volcanoes are not being observed enough. Can sudden small eruptions happen on any active volcanoes?
A: If a volcano has had a relatively large eruption in the past 3,000-2,000 years, it is no wonder that a small eruption like this could happen anywhere at any time. For example, Mt. Yakedake (between Gifu and Nagano prefectures) developed a lava dome on its peak around 2,300 years ago, and water vapor eruptions frequently occurred throughout the 20th century, over 2,000 years after its last major eruption. There could be magma below the ground, which is probably acting as a heat source.
On the other hand, we studied Mt. Nantai in Tochigi Prefecture and found its last eruption had occurred 7,000 years ago. My personal feeling is that it’s not likely to have a small eruption anytime soon.
Some mountains require investigation
Q: In that investigation, you discovered that Mt. Nantai was an active volcano, which means it has erupted in the past 10,000 years or so. Could there be more active volcanoes that we don’t yet know about?
A: There are a few mountains that seem in need of investigation. Volcanoes are usually tourist destinations, which is why some local governments may not want to know the risks of disaster. However, the most important thing for tourist destinations is to protect the safety of tourists.
Since Mt. Nantai was designated as an active volcano, the Japan Meteorological Agency has started observing its volcanic activity. Being able to detect signs of an eruption is beneficial for the region in the long run. On Midagahara plateau in Mt. Tateyama in Toyama Prefecture, a volcanic disaster prevention council comprised of surrounding municipalities distributes pamphlets to people visiting the mountain and warns them about volcanic gases and other dangers.
Properly dealing with the risks allows more people to visit with ease when the volcano is safe. And it allows them to enjoy themselves to the full there.
Q: In that sense, how do you evaluate the measures taken at Mt. Motoshirane?
A: There is snow on the summit for around a third of the year. If an eruption spewing magma in the form of a pyroclastic flow or high-temperature volcanic projectiles occurs, there is a risk of volcanic mudflows caused by melted snow. Our hazard map doesn’t show the potential reach of mudflows from Mt. Motoshirane, so it needs to be added. As observing was strengthened there this time, if the recent seismic activity were to lead to such an eruption, we would probably be able to detect signs of earthquakes or changes in the terrain. We need to continue observing the changes.
Q: Japan does not have many volcanologists. Doesn’t Japan lack adequate staff to cover all 111 active volcanoes in the country?
A: A lot of students come to my lab, but it requires great resolve to progress to a Ph.D because there’s not a lot of security after you get the degree. There are not many jobs where you can use this specialty. I wish the Japan Meteorological Agency and local government disaster prevention departments would hire more volcano experts.
Even if you get a research position at a university, it’s usually only for a set amount of time, so you have to produce results quickly. This is difficult in the field of geological research. The research fund aid system also tends to demand short-term results, so it doesn’t suit this field. If you want to cultivate volcanic geology specialists, you need to give them more time until they can support themselves.
— This interview was conducted by Yomiuri Shimbun Senior Writer Hiroshi Masumitsu.
Mt. Motoshirane alert level ‘2’
Mt. Motoshirane’s volcanic alert level was newly established separately from Mt. Shirane (Yugama) on March 16. The Japan Meteorological Agency announced it is now Level 2 (“Do not approach the crater”), saying, “An eruption similar to the one in January is possible, for the time being.” It is prohibited to be closer than 1 kilometer from the crater where the eruption occurred in January.
Yasuo Ishizaki / Professor at the University of Toyama
Ishizaki is a volcanology specialist who belongs to the Faculty of Sustainable Design at the University of Toyama. He completed his doctorate at Hokkaido University in 1995 and is a member of the Japan Meteorological Agency Volcanic Eruption Prediction Liaison Council’s Kusatsushiranesan committee. He also serves as a member of the Midagahara volcanic disaster prevention council. He is from Tochigi Prefecture. He is 52.Speech