Wednesday, March 21, 2012

Government Officials Declare El Hierro Eruption Over... When It's Not

Apparently under public pressure to declare the resort island of El Hierro "open for business", Government officials in Spain/Canary Islands have declared the alert level at El Hierro be lowered to "green" (the level before the eruption). This occurs as INVOLCAN conducted an R.O.V. mission to the crater, and discovered that yes, in fact, the volcano is still very much erupting, although the characteristics of the eruption has changed. While there is no vigorous "jacuzzi" on the surface, below the water a lot is still going on.

The eruption is very much like the submarine eruptions produced by Loihi on the southern end of the Big Island of Hawaii. Pillow lavas are being extruded onto the sea floor, and continue to do so.

So was this declaration of "green" a politically motivated, and non scientific maneuver? You betcha. I don't think there would be one actual scientist studying this volcano that would say the eruption has ended. If that were true... well obviously lava would not be flowing, now would it?

So the eruption actually continues at this time. The type of eruption this has ended up as is not a Surtseyan eruption, as many people thought might occur, rather the eruption type is called an "Serretyan" type eruption. Earthquake-report.com has a lot more info on this, but I thought I'd share their great image they published on what characterizes a Serretyan eruption.


Descriptive image of a Serretyan eruption, from Earthquake-report.com
El Hierro is a difficult volcano to analyze and monitor as it has turned out to be very unique in its eruption characteristics. Many thought a pyroclastic cone would develop on the island, or that an eruption would ensue in the El Golfo bay (probably because it is shaped like a caldera, even though its just a massive collapse scarp), which actually still has the potential to happen, but it ended up being a very benign submarine eruption that never reached the water's surface. While not an exciting eruption to watch, the concept of this volcano is pretty intriguing, and of great scientific interest, as this volcano is displaying some mechanics that we don't often get to witness.

In any case, if anything interesting happens at El Hierro, I'll be sure to post about it! I simply wanted to share this with the readers to notify that the eruption is still going on, despite what governments may say!


5 comments:

  1. Hey! That is a nice issue... but, can you tell me what causes the formation of floating bombs which arise to the surface in this underwater volcano? Why this doesn’t happen in other situations of submarine volcanism? The magma have the same characteristics: it is basaltic magma in both cases...

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  2. Earthquake-report.com has a full analysis of what causes the lava balloons, but in a nutshell, in this case the magma was highly gaseous and the lava was highly viscous when emitted. You can sort of think of it like blowing bubble gum. As the gas decompresses, the hardened but still very hot lava creates balloons of rock that float to the surface and eventually burst, and the gas can ignite when it hits oxygen. The lavas erupted at El Hierro are a mix of primarily silica, and other minerals, but very mixed overall.

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  3. Yes, I really understand what you're saying... but this should also happen in other cases of submarine volcanism! As I already said, the magma is the same. Supposedly, this magma doesn't incorporate silica of the continental crust , so it's a basaltic magma and this magma don't have so many gases... Right? By the way, can you give me the link of that paper, please?

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  4. Its a very specific type of eruption called a Serretyan eruption, and most submarine volcanoes probably are not close enough to the surface to produce the lava balloons, which at greater depths would be under more water pressure and most likely burst well before they break the surface.

    You might have to sift through reams of posts, but here is the link to Earthquake-report.com's excellent live and daily coverage of the El Hierro eruption. You'll probably want to look for the same date as this blog to find the research paper about the Serretyan eruptions (you'll see the same picture as posted on this blog, with a better explanation than I can provide).

    http://earthquake-report.com/2011/09/25/el-hierro-canary-islands-spain-volcanic-risk-alert-increased-to-yellow/

    Enjoy!

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  5. Yes, I know that type of volcanism. Actually, I'm portuguese and, as you certainly know, the Serretyan volcanism first happened in Azores, and the "Serretyan volcanism" term was created by the portuguese geologist Vitor Hugo Forjaz, that has studied this eruptions in Azores. Yes, maybe depth is the likely cause of the appearance of this lava baloons in just some underwater volcanos... How Nature can be fantastic! Thanks for your help and attention!

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