The Canaries’ tsunami potential. The recent volcanic activity on the Island of La Palma in the Canary Islands triggered a memory that has stayed with me since I read a thriller novel several years ago. In the novel, a terrorist tried to create a gigantic underwater landslide which would result in a massive tsunami aimed at Western Europe and the United States. The site of that landslide was the Canary Islands, or so I thought I remembered. At the time of my reading the novel, I was interested enough to research if such an event would be possible. To my surprise, it was not only possible, but quite likely at some point in the future. Not so much the terrorist part of the story, but the existence of an underwater feature that could produce a tsunami. That’s why it stayed with me, and La Palma was where my memory said it was located.

     Last week, at the height of the reporting on the continuing volcanic activity on the Island, I decided to check and, sure enough, there is a huge, unstable, underwater cliff on the west coast of La Palma.  

     A little background. In 1953, two geologists visited a remote bay in Alaska searching for oil. They noted that in the past the bay had been struck by huge waves, and they wondered what might have caused those waves. The answer came in 1958 at the same place. A huge cliff collapsed into the water and created a wave half a kilometre high that surged through the bay devastating all in its path. This Alaskan example was relatively small, but it dramatically demonstrated the effect of a landslide into the sea. A much larger landslide would cause a mega-tsunami.

     Scientists have since searched the world for sites that could potentially cause a mega-tsunami. In the process they have found evidence of at least 11 mega-tsunamis over the last 200,000 years. The last one happened 4,000 years ago on the island of Reunion in the Indian Ocean. A smaller scale tsunami, such as that created by the explosion of the Krakatoa volcano in 1883, killed 37,000 people. Fortunately, perhaps, there were far fewer people around 4,000 years ago…but not fewer animals!

     Ideal conditions for the creation of a mega-tsunami now exist on the island of La Palma. The Canaries’ tsunami potential.

     The southern volcano on the island erupted in 1949. A huge crack opened across one side of the volcano and the western half slipped a few metres towards the ocean. Scientists believe that the western flank of the volcano will collapse completely during some future eruption and a huge chunk of southern La Palma, weighing 500 billion tonnes, will slide into the Atlantic, creating a mega-tsunami that will move rapidly westwards.

     The colossal energy of the collapse (five thousand trillion joules of kinetic energy) would be converted into a 900 metre-high wave that would travel west at great speed (it would move 250 km in the first 10 minutes). By the time it reached the United States, the wave would be lower (50m high) and wider. It would sweep up to 20 miles inland all along the coast, from Boston to Miami, and destroy everything in its path. Almost every person in the coastal cities will drown.

     Although the main wave would travel west, smaller waves would damage other North Atlantic coastlines. Ireland, Britain, France, Spain, Portugal and North Africa would be badly hit.

     The volcanos on La Palma normally erupt about every 200 years, according to the evidence we have available. Since the last one was in 1949, no-one was expecting a major eruption just yet. The events of last week have blown the “200-year” theory completely out of the water.

     Scientists had also concluded that it might take several major eruptions before the “Big Slide” but their predictions of the next major eruption cycle of 200 years makes you seriously wonder about that conclusion as well. The Canaries’ tsunami potential is growing daily.

     It will happen, the only question is when, and that “when” appears to be creeping closer.

     Time to move a little further inland, me thinks!

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