Why Japan’s deadly Ontake eruption could not be predicted

By Rebecca Williams, (@volcanologist)

This article was originally published on The Conversation on the 30th September 2014. It is re-posted here in order for the article to be updated as further news about the ongoing activity comes in, and analysis by Japanese volcanologists and the JMA are released. 

Mount Ontake, Japan’s second-highest volcano, erupted killing at least 31 people (as of Oct 27th, the death toll is at 57 and 6 are missing) on September 27. Since then, there has been feverish speculation about why tourists were on an active volcano and why the eruption wasn’t predicted.
Mount Ontake (also known as Ontakesan) is a stratovolcano which last erupted in 1979-80 and 2007 (there was also a possible, unconfirmed eruption in 1991). Before this, there were no recorded historical eruptions at Mount Ontake.
Since the eruption in 1980, Ontake has been monitored by the Japan Meteorological Agency (JMA). It has seismometers around the volcano to record volcanic tremors and instruments to measure any changes around the volcano. This would provide the JMA with signs that there was magma movement underneath the volcano and that perhaps an eruption was imminent. There had been a slight increase in volcanic tremors starting at the beginning of September. Why, then, was this eruption not predicted?

No warnings

Firstly, the ability to predict volcanic eruptions is an ambition that volcanologists are far from realising. Magma movement under a volcano will cause volcanic tremor, make the ground rise and fall and release gases such as sulphur dioxide. If these signs are monitored closely, then it may be possible to forecast that an eruption may be imminent.

Safe distance. EPA/Kimimasa Mayama

However, all of these things can also happen without any volcanic eruption. Knowing what these signs mean for an individual volcano relies on data collected during previous eruptive episodes, as each volcano behaves differently. Mount Ontake has only had two known historical eruptions and previous to the 1979 eruption, had not been monitored, so scientists here had no previous data to work with. Volcanic tremors are very common at active volcanoes and often occur without being associated with an eruption.
Secondly, the type of eruption that volcanologists think occurred at Ontake is one that does not cause the signals typically monitored at volcanoes. The images and videos captured by hikers on the volcano show that the ash cloud was mostly white, which can be interpreted to mean that the eruption was mostly steam.
The effects of the pyroclastic density currents, the flows of ash, and gas that flowed over the ground from the summit, suggest that they were low-temperature and low concentration. Both of these point to there being no magma directly involved in the eruption. Instead, it is likely water had seeped into the volcano and was superheated by magma within the volcano and flashed to steam causing what is known as a phreatic eruption. Phreatic eruptions occur without magma movement, hence the lack of precursor signals. The 2007 eruption was also phreatic and also occurred with little warning.

Power of nature

So, if an eruption like the one in Japan could not be predicted, should tourists have been allowed up Mount Ontake? Ontake is a place for religious pilgrimage, as well as a popular destination for hikers and climbers. This is quite common for volcanoes around the world; tourists flock to Kilauea, Hawaii to watch the lava flows, climb volcanoes in the Cascade Range, USA and even ski at volcanoes such as Ruapehu in New Zealand. A phreatic explosion such as the one seen at Ontake on Saturday is possible at all of these places.
There is something compelling about the power of nature, and the beauty of a volcano that draws people to them. Volcanoes are inherently dangerous places and there will always be risks to those who visit them. However, events like that at Ontake are thankfully rare. Laying the blame at the foot of either the hikers, or the authorities that allow tourists to visit active volcanoes would be misplaced.

The events at Ontake were tragic. It’s my opinion that it was a tragedy that could not have been predicted or prevented, given our current level of knowledge. It highlights the need to understand volcanic systems better. My thoughts are with the survivors, and the families of those who didn’t make it.

This article was originally published on The Conversation. Read the original article.

Please post links to updated information in the comments below.

Updates

Latest death toll

It seems that this eruption claimed the lives of 57 people, and 6 others are still unaccounted for. Recovery efforts are expected to recommence in the spring.

'Lessons' in disaster preparedness

The events on Mount Ontake in September have already led to calls for better disaster preparedness on Japan's volcanic mountains. Toshitsugu Fujii, the director of the Coordinating Commitee for Prediction of Volcanic Eruptions, stated in a press conference that he believes there is a gap in the understanding of the commonly used volcanic alert signals. He said "a level 1 danger alert refers to what is 'normal' for an active volcano...in other words, anything could happen inside the crater". He goes on to say that the committee is now looking into the perceptions of these alert levels from those who release them, to those who use them, such as climbers.

Others have issued a call to arms for volcanologists, asking for a national agency for volcanology, rather than research on individual volcanoes being the responsibility of individual university research groups. Shozawa Shin'ichiro states that the only volcanoes in Japan that have manned observatories are "Mount Usu, Mount Unzen, Sakurajima, Mount Aso, and Mount Kusatsu-Shirane" and that "the University of Tokyo, for instance, used to assign instructors and technical associates to its volcano observatories in Kirishima, Izu Ōshima, and elsewhere, but nowadays these facilities are largely unmanned. No researchers were stationed at Mount Ontake, nor are there any on Mount Fuji". Other countries with active volcanoes do have government agencies who are responsible for monitoring active volcanoes, such as the US Geological Survey, who have the Hawaiian Volcano Observatory and the Cascades Volcano Observatory. Currently, in Japan, this responsibility lies with the Japan Meterological Agency (JMA).

There are 35 disaster prevention councils which have been set up to cover 35 active volcanoes across Japan. A survey conducted after the Mount Ontake eruption showed that half of them have yet to set up evacuation plans, though they are considering this and are also considering asking climbers to submit plans before accessing the mountain. These groups also call out to central government for support to improve their disaster preparedness. "If the central government draws up guidelines, it would facilitate the move (to improve disaster prevention measures)," said an official with the Fukushima Prefectural Government, which serves as the secretariat for the Mount Adatara and two other volcano disaster prevention councils.

At Mount Asama, the council have developed a smart phone platform which it uses to alert climbers to weather and volcanic events, if the climber has signed up to the service. However, only a fraction of the mountain visitors have signed up to the alerts. The council are looking at ways to extend the use of its warning system and the JMA seem to be considering rolling it out at other locations. Noritake Nishide, the Director-General of the JMA said that "portable handheld devices such as smartphones should be instrumental in terms of providing information to individual mountain climbers".

Unprecedented coverage on social media
Much of the news of the eruption, and details about the event, were first to be found on Twitter. Hikers on the volcano were tweeting images and commentary during the eruption and this proved invaluable to understanding the processes that occurred. Sadly, recent pathology reports indicate that half of the victims died whilst taking photos of the eruption. Though, apparently Nikon repaired a camera found on a deceased victim, cleaned it and returned it to the family, after recovering some 200 photos. Some survivors found themselves hounded by journalists for details and photos, whilst they were still trapped on the volcano. It led to a lot of armchair volcanology and criticism of the JMA for not predicting the eruption. More thoughts on this below.

Hindsight bias

The article above was largely written in response to several inflammatory articles suggesting that there was someone to blame for this tragedy, or that 'warning signs were missed'. I will not link to those articles here. These types of articles either fall into the trap of thinking that someone must be to blame, or they have looked at the events with 'hindsight bias'. Jonathon Stone has written an excellent article about hindsight bias that I urge you to read here: http://www.nonsolidground.blogspot.co.uk/2014/09/i-knew-it-all-along-avoiding-hindsight.html