“We are powerless in the face of natural forces”

It was a rather bumpy landing. The passengers in the window-seats could see a column of ash rising in the sky. A short time later, La Palma’s airport was closed to traffic. The runways and many of the roads are coated in layers of ash. The eruption of the volcano Cumbre Vieja dominates both the scene and island life. In some places cars, are buried under the black dust, and in some areas the explosions can be heard day and night. “Even for expert volcanologists, every new eruption is a dramatic experience,” says LMU volcanologist Dr. Corrado Cimarelli. Together with his colleagues Drs. Ulrich Küppers and Thomas Kunzmann, he led a group of students on a field trip to the island during the eruption. Here, he talks about his research and his impressions the on the island.

Dr. Cimarelli, you have just returned from an excursion to La Palma. What was the purpose of the trip?

We take our Bachelors’ students on a field trip to La Palma and Tenerife every year. It‘s always a hands-on course. We take the students in the field, and show them what sorts of fingerprints volcanic eruptions leave behind. We analyze the course of past eruptions based on the types of deposits they produced, in order to understand the characteristic features that reveal how the volcano behaves.

The excursion had been planned for March, but had to be postponed until October owing to the trajectory of the coronavirus pandemic. The postponement allowed you to observe the Cumbre Vieja eruption at first hand. Would you describe this as a lucky break?

I would describe it in much more ambivalent terms than that. For us and the students who accompanied us, it was a wonderful research and teaching opportunity. We were on the spot and we could show them everything. A volcanic eruption is a tremendously exciting event. You can hear the eruptions, see the clouds of ash spewing out, and observe the courses of the lava streams. It’s impossible to convey all of that in a seminar room. – And we had the chance to combine on-site tuition and research. We had our research instruments with us, and we were able to support the local volcanologists.

On the other hand, it was terrible to witness at first-hand the damage done by the eruption to the property and livelihoods of many of the island’s inhabitants.

Can you describe the atmosphere on the ground?

The new scoria cone on Cumbre Vieja rises above a group of small villages, which were hit directly. This was the first eruption in Europe for quite some time that demonstrated that volcanos are not only spectacular sights for visitors, but can also present an immediate threat to human life. That’s because, generally speaking, recent volcanic eruptions in Europe have occurred in areas which are sparsely populated.

We encountered some highly dramatic scenes while we were on the island. – A gas station that had been overrun by a lava stream and was burnt down; a house encircled by lava, and in the garden was a paddling pool with toys lying around it; cars that were buried by ash, whole plantations and livelihoods destroyed. That’s not something that one can easily forget.

So far, some 7000 people have been evacuated for their own safety, and about 1300 houses have been destroyed. Meanwhile, new lava streams have developed, which are eating more land further north and south across the island.

These are shocking numbers, especially when one recalls that many of these people have lost the material basis of their existence. On the other hand, the efficiency and professionalism of the local emergency services was very impressive. There has been no loss of human life, evacuations have all been carried out without a hitch and, where necessary, drones have been used to supply stray animals with food. That was very touching to see.

The island’s inhabitants are aware of the eruption risk. Were you able to observe their reactions directly?

We met a whole variety of people during the excursion. But those we were able to speak to were of two kinds. The first were tourists who had lost their holiday homes or apartments. It‘s probably safe to say that they are unlikely to build new houses on La Palma …

But we also spoke with many of the local people, the Palmeros. They accept the risks presented by the volcano. They may lose everything, but they have lived on the island for generations, and their livelihoods are based on what it offers, such as work on the agricultural plantations. Many don’t really have the option to leave the island.

Furthermore, one must remember that a vast portion of the island has been overrun by the lava flows, and it takes a very, very long time before volcanic rock weathers sufficiently to yield a soil that can be cultivated, and the necessary infrastructure can be rebuilt.

In addition to your work with students, you have pursued your own research projects. Your research focuses on lightning. What is the connection between lightning and volcanos?

Lightning is phenomenon that is normally associated with storm clouds. Pliny the Younger, who described the explosive eruption that destroyed Pompeii, also mentions the lightning flashes that accompanied it. Volcanic eruptions have been observed and reported by many people, but our research program at LMU is nevertheless relatively new. Our basic assumption is that lightning is not a random feature of eruptions, but is directly connected with them.

We began to study the phenomenon in our laboratory in the Theresienstraße: Particles of volcanic ash are accelerated into a shock tube and imaged with the aid of a high-speed camera. This enables us to observe the properties of the discharges that develop in the ash cloud. The next stage will involve observations in the field with a view to identifying the parameters responsible for generating the lightning. As part of a large-scale project funded by a grant from the European Research Council (ERC), we have developed a unique set of instruments, with which we can measure and analyze these flashes. We used them on Cumbre Vieja, which provided an unmatched kick-off opportunity for our project.

Can you summarize your initial results?

So far, we have confirmed that the numbers and the sizes of the volcanic ash particles both play a role in determining whether or not lightning flashes are generated – the smaller the particles, the higher the number of flashes.

In the course of our observations, we repeatedly asked ourselves whether or not the size of an eruption has an impact on the generation of lightning. On La Palma, we had the chance to experience a relatively small-scale, explosive eruption, which produced lots of lightning flashes. This essentially confirms our basic assumption. Virtually all eruptions have an inherent tendency to generate lightning. So we now need to exhaustively test and characterize our instrumentation.

How do you go about this in the field?

When we realized that an eruption was imminent, we immediately took the necessary organizational steps to ensure that we could take our instruments with us. On the island, we were in regular consultation with the local authorities and scientists. We were able to set up our instruments in the restricted zone and began to make measurements. The original idea was to bring the instruments back with us, but the collaboration with our local colleagues worked so well that we left them there. We are now working in close cooperation with the researchers on the ground, and we receive all the necessary data from them, which we are now analyzing.

Another aim of our project is to enhance the capabilities of the instruments we have developed, so that they can become part of the standard portfolio of an integrated monitoring package. Their use in the context of an ongoing eruption is an ideal setting in which to demonstrate what they can do.

At the moment, the volcanic island Vulcano, one of the Aeolian Islands off Sicily, is in the news, because a Code Yellow warning has been issued. How does this potential eruption differ from the one on La Palma?

I’m an Italian myself, and as a student I was often on Vulcano. Its most recent eruptive phase took place between 1888 and 1890. Its behavior is characterized by frequent and highly energetic eruptions, so it’s much more dangerous than Cumbre Vieja. However, fewer people are at risk, as the island is visited only in the summer by tourists and Italians who have holiday homes there. Only a few hundred people spend the winter on the island, which makes evacuation easier in the event of an imminent eruption. The authorities have already taken the first families off the island, since the volcano is now making its presence felt. It’s intensively breathing, the floor of the crater has risen by 2 cm, and gases are escaping from vents all around the island. They can become very dangerous if they hang in the valleys or are trapped in cellars.

Of course, Vulcano is ‘the type species’, so to speak. Not only it gives its name to these geologically fascinating objects, but its typical inpulsive cannon-like explosive character was firstly described by Giuseppe Mercalli (the proposer of the seismic Mercalli scale) and gives its name “Vulcanian” to an eruptive style frequently encountered at many other explosive volcanoes of the world.

Areas in the vicinity of volcanos are often densely populated, and their inhabitants are always aware of the risks. Mount Vesuvius, which is frighteningly close to Naples, is a prime example. What might the response to an eruption of Vesuvius look like?

We are essentially powerless in the face of such natural forces. In the case of active volcanos, the only thing we can do is to monitoring them with a dense network of instruments and warning systems. In addition, collaboration with the authorities must be very effective. We have the instruments required to forecast eruptions, but forecasts are very often possible only at relatively short notice. – And Vesuvius presents an enormous organizational challenge. We’re not talking here about a few hundred people, but hundreds of thousands of people who would have to be evacuated.

On La Palma, for example, the magma tends not to erupt very explosively, so there was time to get people out of the danger zone. On Vesuvius, there would have been less time to react, because it’s eruption style would be significantly more explosive. In addition to maintaining its dense monitoring network, it‘s crucial to take a pro-active approach, and ensure that planning policies are designed to ensure that the population density in the areas in the vicinity of the volcano is tightly restricted.