On 19 September, lava came out of the Cumbre Vieja in several places for the first time in fifty years. (Photo: Shawn Appel / Unsplash)
On 19 September, lava came out of the Cumbre Vieja in several places for the first time in fifty years. (Photo: Shawn Appel / Unsplash)

The likelihood of Cumbre Vieja volcano on La Palma exploding and causing a mega tsunami has decreased even further, Delft researchers believe. “Maybe in ten thousand years.”

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The worst tsunami that humans ever saw would threaten the world if La Palma would break in half and partly disappear into the sea. This news went round the world in 2001 after a study by British scientists into the tectonics of the island. The disaster would happen if the sleeping volcano, the Cumbre Vieja, on the southern tip of the Canary Island woke up, wrote the scientists in the journal Geophysical Research Letters. The people on the east coast of North America would have to prepare for a 40 to 50 metre high wave, said the British scientists.

But the calculation is completely wrong, wrote TU Delft researchers in 2006. The island is a lot stronger than the British study assumed. Dozens of assumptions were wrong. And should part of the island break off, it would probably move slowly towards the sea. In other words, not fast enough to cause a mega tsunami. Some other studies at the time drew similar conclusions.

Sitting tensely glued to the TV
Nevertheless, if things start rumbling beneath the island, you still sit tensely glued to the TV, despite all your calculations and simulations. It came to pass on 11 September. The island began to shake, and on 19 September lava spurted out of various parts of the Cumbre Vieja.

“Of course I have followed the situation on La Palma with great interest over the last few days,” says researcher Robert Jan Labeur of the Faculty of Civil Engineering and Geosciences (CEG). In 2006 he was one of the TU Delft scientists that pored over the Cumbre Vieja and the chance of a tsunami. “I know the island’s situation well. In theory, it could be possible that the volcano erupts and that part of the island drops into the sea. But the chance is extremely small. And now that some of the pressure on the volcano has been released, the chance is even smaller.”

Researchers at the University of Madrid have monitored the ground movements of the western slope of the Cumbre Vieja (which has the highest chance of breaking apart) from satellites in space. They use a radar technique called InSAR (Interferometric synthetic-aperture radar) that was largely developed by Professor of Earth Observation Ramon Hanssen (CEG). They concluded that the western slope seems to have become more stable over the last years.

What happens in 10,000 years is a different story, wrote the TU Delft academics in their study. By then the volcano will probably have grown, causing its sides to be less stable.