Explosion off Tonga – volcanologist: “It really must have been a doomsday mood”

A submarine volcanic eruption rocks large parts of the South Pacific. (New Zealand High Commission/ZUMA Press Wire Service/dpa)

The information from the site is still very sporadic, said the volcanologist Thomas Walter from the Geoforschungszentrum Potsdam (GFZ). The first recordings showed that the eruption clouds had risen to several kilometers in just a few minutes. Where the cloud then moved, the sunlight was very clouded. “It’s getting dark during the day as it is at night, and there is no longer any visibility. That must have been a doomsday atmosphere,” said Walter.

According to Thomas Walter, the region of the eruption is part of the Pacific Ring of Fire. “This is a series of numerous, actually most active, explosive volcanoes in the world.”

Possibly “biggest eruption in recent decades”

The blast height could actually be historic, according to the volcanologist. Latest data indicated that it climbed 31 kilometers. “And that would actually make it one of the largest eruptions in recent decades.” The number of flashes was also noteworthy. A total of 400,000 flashes were measured in the first 12 hours on the Hunga Tonga-Hunga Ha’apai volcano. “And that shows the dynamics of the outbreak.”

With Lightning and Thunder – The Unusual Outbreak of Hunga Tonga-Hunga Ha’apai

On January 15, there was nowhere on earth with more electricity. “It was literally crazy,” explains mineralogist Corrado Cimarelli from the Ludwig Maximilian University in Munich. “Our networks have counted record rates of four, five, six thousand flashes per minute, which is ten flashes per second, which is something you would never expect in a thunderstorm.”

The full text of the interview

Thomas Walter: The eruption occurred in a very remote area, which is not really the subject of intensive on-site monitoring, and also shows us that hidden volcanoes in particular can trigger dramatic eruptions. The height of the eruption was more than 30 kilometers, according to the latest data.

bold: What exactly happened that it could be of such magnitude, and why exactly there?

Walter: The region is part of the Pacific Ring of Fire, which is a series of numerous, actually most active, explosive volcanoes in the world. We know of 450 active volcanoes there, some of which are dormant, that is, in a temporary state of dormancy, some of which are erupting. There in the region it is a so-called subduction zone, which means that the Pacific plate is submerging and is generating this volcanism at this interface.

bold: In the discussions on the Internet and in social media, some people are already suspecting that it was an eruption that only occurs every 1,000 years. Is that so?

Walter: It’s hard to say at the moment how big the eruption actually was, because here we have the interaction between magma and water. Water develops a very high explosive power when it is heated to high temperatures. You can imagine a liter of water, when it is converted to steam, we have an almost thousand-fold increase in volume. That certainly played a big role here. The eruption height here was likely well over 20 kilometers high, with recent data suggesting it went as high as 31 kilometers high, making it indeed one of the largest eruptions in recent decades. But as I said, in order to assess how strong the eruption actually was, you have to wait and see, because other measurement data are also included, not only the height, but also the volume, the duration of the eruption and other things.

“Over 400,000 flashes in the twelve hours”

bold: That was also very spectacular, the tension that was released there, i.e. thousands, if not hundreds of thousands, of flashes. Do you already have numbers or clues?

Walter: The lightning observation of volcanoes is a very important element, which we can now do worldwide with a very high degree of accuracy and reliability. There is a flash monitor globally, where various data are also collected. In fact, more than 400,000 lightning bolts were measured on the volcano in the twelve hours. That already shows the dynamics of the outbreak.

bold: When we looked at this from a bird’s eye view, it was very, very impressive. How must it have felt for the people on site – also with a view to these discharges – almost apocalyptic, yes.

Walter: So the first information was also shared via social media and showed recordings, including video recordings from ships. They showed that within a few minutes the eruption clouds had risen to a height of several kilometers, maybe ten to twelve kilometers. Lightning did not appear at that time, but we can see that the first lightning appeared at this point in the first few minutes. This is mainly seen from satellite data. There, where the cloud has been transported, the sunlight has certainly become very clouded, it is dark during the day as it is at night and it is usually no longer visible. That really must have been doomsday mood.

“Data still very thin”

bold: The volcano had already stirred in December, then it was quiet. And suddenly, that was my impression, the big bang came. Was that so?

Walter: Exact advances are very difficult to assess simply because there was no properly functioning local surveillance system. Basically, major volcanic eruptions are already on the horizon, simply because magma accumulates underground, the volcanism that we see on the surface is ultimately the final stage in a long chain of events. Thus, such large eruptions usually announce themselves. In this case, the data is still very sparse, it has to be said, and we are still trying to get better information, including from the neighboring islands. But at the moment one cannot really say how strong the signs were or even whether the population was really warned in time.

bold: What is the question that is most important to you at the moment, where you would have quick answers?

Walter: A tsunami was also triggered here during the eruption. Basically, in volcanic tsunamis that are generated by explosions, the wave heights are relatively low, simply because they are point sources and therefore disappear very quickly. In this case, considerable wave heights have also been measured off Japan. That is now one of the big questions, what ultimately led to this tsunami. I can only speculate at the moment, I suspect that it has less to do with the explosion itself and more with ground movements. But future studies are certainly still necessary to substantiate this or suggest another solution.

Statements made by our interlocutors reflect their own views. Deutschlandfunk does not adopt the statements of its interlocutors in interviews and discussions as its own.


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