Today, I would like to share with you an interesting article, about an island in the southern Spain.
The last of the 20 megagliding, that have been documented, in the geological past of the Canary Islands, which opened 80,000 years ago the valley of El Golfo, on El Hierro, has moved double rocks and materials, than which was estimated so far: 318 km3, almost 6% of the total volume of the island.
El Hierro island with the Valley of El Golfo
The megagliding of volcanic islands happen to be one of the most impressive phenomena of nature, or, at least, that is deducted by scientists for the "scars", left in Hawaii, in Cabo Verde and in the Canary Islands, because none of them has occurred in a recent past.
The scientific consensus believes these gigantic collapses of land occur because the volcanic islands grow so fast and so vertical, the base does not withstand the weight and its slopes can collapse suddenly, if they are destabilized by other natural phenomenon, like an earthquake, a rash or millennia of internal erosion by groundwater aquifers.
Slopes over the Valley of the Gulf
The latest studies on the gliding of El Golfo, published in 2011, date in a period between 39,000 and 97,000 years ago, and they estimated that it caused an avalanche of 150-180 cubic kilometres of land.
Rocks on the Valley of the Gulf
This spectacular gliding, occurred after collapsing the northern slope of the volcano of El Golfo (the volcano Tiñor), which had grown over 400,000 years, on the plain left by another megacollapse, 600,000 years ago.
Gully Tiñor
Megagliding of land
The authors review thoroughly the final collapse of the youngest of the islands of the Canary Islands, using seismic data, provided by the National Geographic Institute, the bathymetry and echo sounders, carried off its coast, by the Navy and the Spanish Institute of Oceanography (IEO) and a detailed study of the geology of the walls of the Gulf, forming an amphitheater of 15 kilometres amplitude, and all its water wells and galleries.
Their first conclusion is that the megagliding of the Gulf was, in fact, the succession of two collapses, separated only by "a few thousand years", that left, as a mark, on the north of the island, two overlapping natural amphitheaters: the first cast, on the Atlantic, about 243 km3 of rocks and, the second, about 84 km3.
Only the smallest, of those collapses, suddenly moved such volume of material as it is estimated that, in the worst case, the Vesuvius expelled, in eruption that buried the Roman cities of Pompeii and Herculaneum, in the first century or what is the same as 55 times the capacity of Mequinenza swamp, the largest reservoir of the Ebro Valley.
Panoramic views of the Valley El Golfo
The three scientific institutions, involved in this study, have also revised underground galleries, in which several marine deposits following that collapse are appreciated, that were covered by other eruptions, in El Hierro, later. In them, they have found areas of erosion that allow them to calculate that the collapse of El Golfo happened between 23,500 and 82,500 years ago.
The characteristics of the remains, buried by lava, lead them to think of a time with the same sea level than today, among the last two ice ages, so they consider that the most likely is that all happened about 80,000 years ago.
As for the remains found under the sea, the proportions which those reveal, on this megagliding, they are not minor: the northern slope of the volcano of El Golfo generated an avalanche of boulders up to 1.5 kilometres long and 300 metres high .
Finally, the article announces that possible remains of more recent undocumented landslides have been found, in that area of El Hierro, so the landslide of El Golfo would not be the last one.
That would explain the datings, offered by the registration of undersea deposits, caused by ancient tsunamis, that exists in Madeira funds, to the north of the Spanish archipelago, suggesting that other megagliding, occurred in the Canary Islands, about 17,000 years ago.
Well, I hope that you have considered this post as interesting as I do.
Until my next post, kind regards,
Luis.
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