Canary Islands Seismicity


It has been brought to my attention that there has been elevated seismicity on the island of El Hierro in the Canary Islands, the bearer of that news transmitting with it considerable alarm over what might happen there, suggesting it might equal a super-eruption of Yellowstone. Well we never know what might happen, but  we do know that flying into a panic will in no way serve us, and personally I do not care to engage in scare-mongering.

So I went looking for facts. It has been reported by according to the Instituto Geografico Nacional (IGN), that over the past 5 weeks over 4200 small quakes have occurred at El Hierro, most of them under magnitude 1, and the largest of them being magnitude 3.5 on August 22nd. That’s the newest information I could find about the quake swarm there.

Here is a map of the island showing the quakes mapped up until the end of August, or thereabouts, (click for larger image) First off, a swarm of small quakes on a small island in the Atlantic does not a global catastrophe make.

The Hierro shield volcano on the island  is truncated by a large NW-facing escarpment formed as a result of gravitational collapse of El Golfo volcano about 130,000 years ago. Hierro contains the greatest concentration of young vents in the Canary Islands. Uncertainty surrounds the report of an historical eruption in 1793, and a small eruption, during the 18th century, produced a lava flow from a cinder cone on the NW side of El Golfo.

It may be that the recent upswing in seismicity there is a precursor to renewed volcanic activity and might indicate rising magma. Worst case, the old El Golfo vent might open up again and build a new cone over time. Understandably officials there are nervous and uncertain where this is going, and the Canary Islands government has convened meetings to discuss it. The Instituto Volcanologico de Canarias has also reported a 1cm inflation over part of the island’s volcano following on from GPS analysis. That would be on the east end of the island seen above.

It is claimed on one website that a massive landslide originating in the area of the quakes gave rise to a 100 meter tsunami 50,000 years ago, but I have been able to find no other information on that. If it did happen that land has already slid, so I’m not going to trouble myself about it.

Certainly, the alarm over the quake swarm at El Hierro ties in with the big scare that was going around online some years ago over claims that giant volcanic mountain Cumbre Vieja on La Palma, also in the Canary Islands, was going collapse and slide into the ocean generating a giant tsunami that would race across the Atlantic at over 600 mph and hit the east coast of the U.S.

These claims were shown to be nothing more than shabby attempts at sensationalistic scare-mongering by certain “scientists” seeking to stimulate funding for their own research projects on which they might have lived very well indeed. Not the last time that’s been tried, and the recent seismic activity at El Hierro seems to have revived that scare to some extent among those still waiting for the big disaster from the Canary Islands.

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About Martina Vaslovik

Volcano nerd and seismogeek
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