There is nothing we can do about flank collapses except have a good early warning system.
Don’t worry about it ”, the mainstream media are running the risk that the volcanic eruption in La Palma, in the Canary Islands, turns into a mega-tsunami. The media definitely overstated this risk when it was first suggested twenty years ago, so now they have to work across the street. But the original story still has legs. The eruption is now over two weeks old, but explosions and lava flows continue to increase. Part of the main cone of Cumbre Vieja (old summit) collapsed a few days ago. La Palma and its neighbor El Hierro, the westernmost islands of the Canaries, are so volcanic that similar cone collapses have removed about half of their mass above the water over the past million years. Volcanoes are constantly rebuilding islands too, so massive landslides are an integral part of their geology. This is why the volcanologist Joan Martí, when asked if the side of the Cumbre Vieja could slide into the sea and cause a huge tsunami, replied that “it is possible, but it is not probable” . But there will eventually be another collapse in La Palma, then a tsunami, maybe tomorrow, maybe 100,000 years or so. The original scientific article warning of a possible La Palma mega-tsunami was written by Steven Ward and Simon Day in 2001.
They estimated that the giant waves generated by a flank collapse would hit the Moroccan and Spanish coasts in two to three hours, and would cross the Atlantic to hit the Brazilian, American and Canadian coasts in nine hours. From a height of hundreds of meters at first, the tsunami waves would have probably reached a hundred meters when they reached Spain, and perhaps only 25 meters high when they hit the North American coast. from Florida to Newfoundland. But it’s still a lot. At least that’s what Ward and Day estimated – what other scientists immediately crammed into to insist they were wrong about the geology, or the volcanology, or the speed at which the waves. tsunami lose height over long distances. What the media missed was that all the basic facts were correct: the relatively frequent massive landslides (one every 100,000 years in the Canaries, on average), the ensuing tsunamis and the immense damage that they speak. The chances of this particular volcanic eruption causing a mega-tsunami are less than one in a hundred, maybe one in a thousand. Even if a La Palma tsunami hit the Americas, wave heights could be less than one meter. But the risk of unpredictable life-changing events is real. There is nothing we can do about flank collapses on volcanic islands other than having a good early warning system, but they are only common in the Hawaiian Islands, the Canary Islands, and the Indonesian archipelago. Then there are the asteroid strikes, the global plagues, nuclear winters, but let’s stick with volcanoes. Just east of the Rocky Mountains in the west-central United States, Yellowstone staged three long-lasting “super-eruptions” 2.1 million, 1.3 million, and 631,000 years old. Each time, it blanketed the surrounding states with a meter thick volcanic ash, smeared the entire continent with enough ash to kill most of the green plants, and grew over a thousand cubic kilometers. of pulverized rock and gases in the atmosphere. This blocked out much of the incoming sunlight for the next six to ten years and caused a “volcanic winter”, with an average global temperature 3 or 4 ° C lower. If that happened today, it would lead to global crop losses and massive famine.
(Gwynne Dyer’s new book is ‘The Shortest History of War.’ The opinions expressed are personal.)