Wednesday, October 27

The questions about volcanoes that science still can’t answer

Living on the slopes of a volcano obviously involves a very high risk. The inhabitants of the areas affected by the lava flows and pyroclasts from the spectacular eruption on the beautiful island of La Palma are experiencing the loss of their homes with grief.

Given this, it is science that must lend a hand. An informative hand. Because science can only aspire to understand in order to explain the processes of nature, because it cannot stop it; neither a volcanic system like this one, nor the atmospheric dynamics that a typhoon generates, nor the lithospheric dynamics that move some tectonic plates closer and further away from each other. We can always study and understand to react better, but never stop.

Explain the rash

Little can be added to everything mentioned and described up to the moment of this eruptive episode. Much has been explained in early boat interviews (some on the ground) by technicians and scientists. They have made an effort to also attend to this information front, at any level of knowledge, from the dissemination for school children (what is a volcano, the difference between magma and lava …), to the most advanced scientific detail (chemical composition, mechanisms of degassing, satellite images, monitoring activities …). But all this does not seem to help what is necessary.

The eruption by definition in Geology is from effusive to slightly explosive because the magma that feeds it is of basic composition, that is, poor in silica and not very viscous and, therefore, of fluid lava emanations. This chemical composition of magma can fuel strombolian-type eruptions as in the case of La Palma, or Hawaiian type – what we all recognize as “open taps” of fast-flowing lava on the Hawaiian Islands.

The strombolian ones compared to the Hawaiian ones are only slightly more explosive, and with a slightly higher fragmentation and dispersion capacity of the ejected material and the height of the eruptive column. They are far from the explosive capacity of Vulcanian, Plinian or Peleano type eruptions, for example, with viscous lavas and very violent eruptions (such as those of Vesuvius, Santa Helena, Pinatubo, etc). Or even those hydromagmatic eruptions in which the water-magma interaction can generate very explosive eruptions.

In fact, if La Palma were an uninhabited island, we would simply be enjoying (science and tourism) the wonders that nature gives us from time to time: a “quiet” volcanic eruption at hand (or selfie). However, with human lives in danger, this information and details offer little comfort and have not satisfied the curiosity (need?) Of society about when, what day, will the volcano cease to roar for good.

The specialist’s scientific explanation aims to provide sufficient knowledge tools for society to find the balance between staying alert and maintaining enough serenity to react efficiently, being aware of such a particular scenario (we are talking about a volcano that affects inhabited municipalities ).

Questions without answer

Unfortunately, science still has no answer to the two key questions in volcanology:

  • when and how the priming of the magma chamber occurs in depth that generates and feeds the eruption on the surface,
  • and at what moment the eruptive activity, mainly of solid material, ceases.

For the first question, science has the details studied in previous eruptions together with monitoring tools that, in the case of La Palma, have worked perfectly to alert the population that the volcano was getting nervous.

Up to 15 cm of deformation (bulging) of the ground and eight days of earthquakes have led to the eruption. Honestly and humbly, we must admit that we did not know if 4, 15 or 40 cm, as well as 5, 8 or 100 days of earthquakes would be the precise ones before the eruption. This is where all research groups worldwide must continue our scientific efforts.

As a close example, the contribution of our group from the Geology Department from the University of Salamanca to this desired prediction focuses on comparing the arrival of the geophysical signal (earthquakes and deformation) with the geochemical signal (release of mantle gas when the magmatic chamber is destabilized before the eruption is already underway). We check in the case of Tagoro (island of The iron) in 2011 how the geochemical signal warned geophysics in advance of the arrival of what was the last (underwater) eruption in the archipelago.

For the second concern, it is not necessary to be a scientist to assume that volcanic activity ends when the magmatic reservoir empties sufficiently to relax the internal pressure that destabilizes it. And science has yet to predict this checkpoint.

A punctual stop in the emission of lava like the one that happened yesterday on La Palma it can indicate the beginning of the end of the eruption, or the beginning of the end of an eruptive pulse awaiting the arrival of a new one.

From now on the first emergency will be to attend and compensate the affected families as much as possible. Later, when the material has cooled a bit, carefully read the information that the interior of the planet has written to us in the material expelled by this eruption.

The rocks (pyroclasts and solidified lavas) and their components (minerals and volatiles included) are the witnesses of what happened in depth, before and during the eruption. Studying them, we will be able to better understand the eruptive process under La Palma, so that science continues to advance and get closer to better constraining the conditions in which the next eruption will occur, aware that it will arrive without man or science being able to stop it. The impregnable nature.

When all this is over, we will have more knowledge tools to face the next eruption, in general, and on La Palma, in particular: a landscape, as well as a topographic-geological map, new or modified, but just as beautiful.

This article was originally published on The Conversation. You can read it here.





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