interview
The lava reached the first houses in the coastal town of Grindavik and set them on fire. Scientist Troll hopes that the volcano will calm down again soon – but assumes that there will always be eruptions.
tagesschau.de: Did this new outbreak surprise you?
Valentine Troll: Actually, he didn’t surprise me. We had been waiting for new outbreaks in the area for a week or two. There have been repeated outbreaks since 2021, and we expect further outbreaks in the near and even some distant future. The activity on the Reykjanes Peninsula will probably continue for several years with small outbreaks, which unfortunately can also affect towns and infrastructure.
To person
Valentin Troll is a professor at Uppsala University in Sweden. He specializes in volcanic rocks and volcanic phenomena. He completed his studies at St. Andrews University in Scotland and received his doctorate from the GEOMAR Research Center at the University of Kiel. During this time Troll taught volcanology and petrology at Trinity College Dublin. He completed his habilitation at the Blaise Pascal University of Clermont-Ferrand, France.
Small openings in the earth’s crust
tagesschau.de: What is special about this volcano?
Troll: The Reykjanes Peninsula lies on the spreading zone between two major tectonic plates, the North American Plate and the Eurasian Plate. There it is the case that the plates not only move apart vertically, but they also rub against each other. And of course that leads to small openings in the Earth’s crust as the plates move. Then the excess pressure that exists in the magma reservoir – in the magma chambers – is discharged through small eruptions.
Once an eruption occurs and the pressure is released, it has to build up again and so I think we will be dealing with several smaller eruptions over the next few years.
“The whole peninsula has a rhythm”
tagesschau.de: You’ve been watching the volcano for a long time – does it perhaps have a recognizable rhythm?
Troll: Yes, the whole peninsula has a rhythm. Geologists have studied the last 3,000 years and have found that the entire area is episodically volcanically active. There are periods when nothing happens for about 800 years, and then there are periods when there is a lot of activity that last 200 to 300 years. This has now repeated itself several times in these exact cycles.
And in 2021 it started at Fagradalsfjall, and we now expect that there will now be a larger cycle in the area that will continue to develop over years, decades, possibly a century or two.
Several small volcanoes are likely to erupt
tagesschau.de: What does that mean? Now if you say there will be a cycle, that means there will be repeated earthquakes in this area and the volcano will erupt again and again?
Troll: Probably yes. It won’t just be one volcano, it will be several small volcanoes. There are five volcanic systems on the peninsula, and it will probably go back and forth a bit. Once it’s this one, then it’s the next. This will probably continue for quite some time and we will have smaller volcanic eruptions there.
tagesschau.de: How exactly can you predict when an outbreak might happen again?
Troll: Volcanologists can now predict this relatively well. We knew that there would most likely be an eruption in the Grindavik area now. We’ve known this for weeks. I actually thought it would start a few days ago. It has now taken a few days longer, but the data, ground elevations, seismic activity, earthquakes, temperature developments, gas emissions, all this data is being collected and of course it points to certain events.
Accordingly, it was also possible to evacuate the place in time. And so far no one in the population has been harmed by the direct volcanic activity. Unfortunately, there was an accident during clean-up work a few days ago that was probably fatal. But that wasn’t directly due to volcanic activity.
People avoid volcanic areas
tagesschau.de: What does that mean for the people who live there? Is this piece of earth still habitable?
Troll: Yes, of course the area is habitable. The example of La Palma shows what can happen. There was an outbreak there two years ago. Some people then no longer wanted to live there. If the eruption or eruptions only occur irregularly with long periods between eruptions, then people can still come to terms with it. But if it happens every few months that a small volcano erupts somewhere and you don’t know exactly where it is happening, then I expect that some people will migrate from the area.
Psychologically, I think it is very difficult to live with this uncertainty, and it is well known from volcanic areas, which are often affected, that people also migrate and that the places then slowly lose their residents, infrastructure and, accordingly, economic power .
Protection against toxic gases
tagesschau.de: What is dangerous about outbreaks like this? Is it perhaps gases that are created there, the lava that reaches the houses? What are the dangers for people?
Troll: Volcanoes are divided into different types. The volcano here is a fissure volcano. And there the main danger is the lava emission, that lava flows down the slope and towards towns, as has now happened in the coastal town of Grindavik.
Gases can also escape and if the wind direction is unfavorable, then the gases can of course also drift towards residential areas and then severely affect the air quality. The wind direction in this area is often towards the south, so the gases are blown out to sea. Then of course it’s not particularly harmful. But if the wind changes temporarily, toxic gases can also be blown into Reykjavik, the capital.
But the wind is very strong and the gases are often diluted. By the time the toxic gases reach Reykjavik, there will probably no longer be a high concentration of toxic substances in the air. But in the immediate vicinity this could of course be problematic. The protection authorities, the fire brigade, the police, have to go into the areas around the volcano with gas masks in order to protect themselves – so such dangers can occur locally.
Protective dams against lava masses
tagesschau.de: And the lava flows, can they be diverted?
Troll: There are different types of lava here too. For example, there is knitted lava and pita lava. It is relatively thin, flows very quickly and can be redirected. Then there is another type of lava, the block lava, which is more like a tank track that moves forward. If enough lava comes out, it can hardly be stopped. Higher dams can then have a temporary effect, but not in the long term. Dams have been built around Grindavik in recent weeks because this eruption was predicted or at least expected.
The first fissure that opened sent lava towards Grindavik and could be diverted through this dam. But then cracks opened up within the ramparts and that’s why there are now lava escapes that are closer to the town, behind the dam and so the first houses are affected and burn.
“There remains hope that the volcano will calm down quickly”
tagesschau.de: If you look at your measurement, what will happen in the next few days?
Troll: The first developments show that the intensity of the outbreak has decreased somewhat. There is now hope that the eruption will calm down somewhat. If you look at the eruption on December 18th in comparison – the eruption only lasted three days.
Likewise in the summer of 2023. The entire outbreak activity subsided in two to three weeks. So we hope that things will calm down very quickly. And then large parts of Grindavik could be spared. Of course, if eruption activity continues in earnest now, if enough lava is produced, then larger parts of the town could be destroyed. We can only hope that the volcano calms down quickly.
The interview was conducted by Anja Martini, science editor tagesschau. It has been edited and shortened for the written version.