According to the Express website, La Palma is being “smashed by hundreds of earthquakes from the deadly Cumbre Vieja.”
We’ve been so thoroughly smashed that I haven’t felt a thing. Literally nothing. Not a sausage. The biggest we’ve had was a 3.5 magnitude earthquake and that doesn’t “rock” anything. Most people didn’t noticed it at all. The others were magnitude 1 or 2. I should mention that it’s a log scale: a magnitude 1 earthquake is 10 times smaller than a magnitude 2. Damage starts at about magnitude 5.
I have a geologist friend called Gerard, who’s doing a master’s thesis on the Cumbre Vieja for the OU. He helped me understand what’s happening down there.
Yes, we’ve had over 100 tremors. The magma is gurgling around down there, and it might even be rising, but the movements are 27 km below sea-level. At that depth, the pressure is tremendous and the magma is more solid than liquid. Before there’s an eruption, this almost solid magma has to force its way to the surface through solid rock. (OK, when it gets to a zone called the adiabat the magma becomes more liquid due to the decrease in pressure. That’s about 11 km below sea-level.) The journey to the surface takes years and there’ll be earthquakes all the way. If we get a series of earthquakes getting steadily closer to the surface, more powerful, and longer lasting, then I’ll worry. But magma rises slowly, that we should have at least 44 years before it gets as far as the adiabat, and longer before anything goes BANG. As Gerad says, plenty of time to finish your beer.
How bad would an eruption be?
Well the Teneguía eruption, in 1971, was a very nicely behaved little volcano. It’s a very sparsely populated part of the island. It made a mess of vineyards and the salt works, and I believe they had to evacuate some goats. To be honest, I could quite fancy seeing an eruption that size, and other people agreed: it was a tourist attraction at the time.
The underwater eruption on El Hierro caused almost no direct damage. The tremors were alarming – the biggest was 5.5 magnitude, and some sent large rocks careening down a cliff into someone’s house although no body was hurt. They had evacuation plans ready, but didn’t need them. The worst damage was economic. Ridiculous hype in the media scared the tourists away, the sulphur that eventually erupted scared the fish away, and the slightly warmer air over the island scared the clouds away which meant a very dry winter.
The 1949 San Juan eruption made a much bigger mess, but nobody was killed. In fact, La Palma’s had 7 historical eruptions and only one person has died. From memory, just 14 people have been killed by eruptions in the Canary Islands.
And the mega-tsunami thing?
Yeah no. According to Gerard:
The Cumbre Vieja is stable, and the crack that some people mention occurred in 1949, it is depending on where you measure it from 1&1/2 or 2&1/2 km long. It does not run the length of the Cumbre Vieja – that is about 25 km long! The crack was reported by a local geologist – Juan Bonelli-Rubio in 1949, as being “1&1/2 km long about 2 metres deep and about 2 metres wide”. It still retains those dimensions with no indications of any motion. In fact there is a large number of geologists, myself included, who consider that the there is no risk for the foreseeable future of a collapse. One study indicates it could be about 10000 years in the future.
Again, plenty of time to finish your beer.
If you want to keep an eye on this, don’t pay any attention to the Express or Sun. Remember when Obama was introducing the Affordable Care Act and Fox News was wall to wall bollocks about the NHS? That’s about the level of trustworthiness. Try the Institute of Volcanogy of the Canary IslandsInvolcan, or the Plymouth Herald who had a much more sensible article.
Meanwhile, I could use that beer. It’s been really hot today.