Scientists have found that 73,000 years ago, a slope from the volcanic island Fogo in the Cape Verde islands off the coast of Africa fell into the ocean and caused a tsunami, the Washington Post reports.
"You're displacing a huge mass, which must generate movement of water," Ricardo Ramalho, the lead researcher behind the study, told The Washington Post.
"And in the case of volcanic flank collapses they can be very acute, because you have all this mass collapsing basically into the oceans."
Ramalho published the work along with a team of researchers from Columbia University as well as several universities in Portugal and Japan.
The study was published in the journal Science Advances.
Scientists say that the powerful tsunami wave must have surged over the top of a more than 600-foot high cliff, attaining water levels nearly 900 feet above sea level.
In 2007, Ramalho saw large boulders on top of the high plateau in Santiago that ended in a steep cliff face and was puzzled by their origin. Ramalho and his colleagues decided to take a closer look at the boulders and other associated geological evidence at much higher elevations. There was also strong evidence that Fogo had undergone a partial collapse, which the scientists connected with the occurrence of a megatsunmsami.
Ramalho and his colleagues now assert that the boulders must have come from far below, up the side of a sheer vertical cliff, a feat that could only be achieved by a megatsunami.
The researchers conclude that tsunamis may occur on certain volcanic islands. They encouraged the study of volcanic islands so as to "realistically assess the full hazard potential of such low-probability but high-impact events."
"I'm not saying that this is going to happen on Fogo or elsewhere, tomorrow," says Ramalho. "I'm just saying, this happened in the past, so we need to be vigilant."
