Scientists warn Canary Islands volcano could generate large tsunami

Subsequent studies have shown that hillside collapses occur regularly throughout the Canary Islands. “However,” he told DW vulcanologist Thomas Walter, professor at the German University of Potsdam, “these rock masses will probably not slide in a single block, as expected, but in several smaller “. So “the problem cannot be completely ruled out”, adds the geological risk specialist.

What happens is that “No one wants to hear that he lives under such a drastic threat”Walter laments, and emphasizes that “thanks to excellent management”, the current eruption on La Palma has not killed anyone.

Volcanology has progressed over the past 20 years. “Today we can get data from satellites and radar that allow us to see through clouds, even through smoke from craters, and scan the ground.” says Walter, a member of the IPOC Volcanoes Watch Network.

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The large volume of thick lava reaching the sea hides another danger, in addition to the more obvious one of direct destruction by contact.

Predictions in volcanology, as well as in meteorology, are also based on history. And although each volcano has its own “character”, the German volcanologist considers It is important to take into account the lesson left by one of the most famous volcanic islands, Krakatoa, in Indonesia: “The collapse of Krakatoa, which is much smaller than La Palma, generated a large tsunami ago. 140 years “. The island collapsed into a caldera in 1883 and reappeared above sea level in the 1920s.. Since then, there have been several landslides that triggered small tsunamis.

“A team of Italian vulcanologists then carried out the most precise seismic measurements ever made in Krakatoa, but the study was ignored. Until the collapse of the flanks of the volcano, which caused a tsunami of great proportions in December 2018 ”, warns Professor Walter.

Is it currently possible to make a forecast for Cumbre Vieja? “It is not yet possible,” replied Walter, of the Helmholtz Alliance on Remote Sensing (EDA), adding that “there has been no experience of flank collapse in La Palma in the past. .. What we know is the volume of the old quiet neighborhoods ”.

According to Professor Thomas Walter, Volcanologists around the world have wondered for 22 years how big a tsunami could be, if produced, how far submarine sediments will be transported and what is the magnitude of the pressure release in the system magmatic. But, despite the progress, “the data are still scarce to be able to give precise answers”, emphasizes the scientist. Cumbre Vieja, like other volcanoes, still holds many secrets.

What seems clear is that no major earthquakes would occur in La Palma in the future. Because? Professor Walter explains: “The conditions for an earthquake of magnitude 8 on the Richter scale to occur, for example, have to do with the proximity of large continental faults and the flow of magma, withor in the Pacific, off the coasts of Latin America and the Andes, Japan or Indonesia”. Walter explains that “The Canary Island of La Palma is so small that it is simply impossible for it to generate so much energy”. This does not mean that magnitude 5 tremors do not cause damage.

For the moment, until September 22, “the lava flow had somewhat reduced its speed on La Palma”, adds the expert, to whom “It is surprising how many houses have been destroyed”, which were built in the areas of lava flows, and approved by the authorities, despite all the scientific studies.

Professor Walter finds, anyway, “admirable”, that the inhabitants of La Palma accept to live with risk: “The Canaries know very well that they live on active volcanoes. This is what the fertile land gives them, and it is the source of tourism. Corn They are also aware that whatever the volcano gives, can again be taken away. at any moment”.