Message #262300

[Apocalypse]

Debris discovery
Related stories

    Switzerland braces for Alpine lake tsunami
    Planetary disasters: It could happen one night
    Realities of risk

More related stories

In 2011, a team of European geologists published evidence3 of moderately sized tsunamis hitting Santiago Island in Cape Verde, an archipelago country off the coast of Senegal. According to the paper, the events occurred around 100,000 years ago as the oceanic volcano Fogo gradually collapsed 55 kilometres away.

As he read that paper, Ramalho remembered that, while he was conducting PhD research on Santiago Island in 2007, he had noticed mysterious boulders strewn across a wide plateau around 200 metres above sea level. He realized that to rip the rocks from cliffs and push them so far upwards would have required a much larger wave than the ones suggested by the 2011 paper.

Ramalho and his colleagues went back to Santiago and took samples of the boulders. They found that they were composed of a type of rock that was otherwise found only around the edges of the plateau. A trail of chaotic debris — including marine fossils — also pointed to a tsunami. They calculated that a wave powerful enough to carry the largest boulder would have been at least 170 metres tall as it reached the coastline, sloshing up the island to reach elevations as high as 270 metres.