Rising from the Atlantic ocean, hundreds of miles off the coast of West Africa, there’s a volcano with a 73,000-year-old scar swiped across its face. This is the mark of an ancient catastrophe, etched into the rock when a huge chunk of the volcano’s eastern flank rushed all at once into the sea.
That particular flank collapse displaced enough water to generate a powerful tsunamione that, new evidence shows, might have been much, much bigger than geologists previously believed. Our work provides evidence that the well-known collapse at Fogo volcano produced a very large tsunami that impacted the nearby island of Santiago, said Ricardo Ramalho, an Earth-sciences research fellow at the University of Bristol.
Very large, even by tsunami standards, seems like an understatement here.
Ramalho and his colleagues identified giant boulders almost half a mile inland, hundreds of feet above sea level, that they believe were transported by a mega-tsunami. Based on what they found, the scientists believe the tsunami swelled to a height of about 560 feet, tall as the Washington Monument, before inundating the island. These characteristics make this event one of the largest mega-tsunamis preserved in the geological record, Ramalho and his colleagues wrote in a paper about their findings.
Flank collapses like the one that decimated what is now Santiago are rare, but not unheard of. Hawaii has its own history of mega-tsunamis, most recently about 100,000 years ago. One block of rock that slid off Oahu is the size of Manhattan, wrote Becky Oskin in Live Science.
Flank collapses like the one that decimated what is now Santiago are rare, but not unheard of. Hawaii has its own history of mega-tsunamis, most recently about 100,000 years ago. One block of rock that slid off Oahu is the size of Manhattan, wrote Becky Oskin in Live Science.
2015 by The Atlantic Monthly Group