Whether a volcanic eruption was violent with high dust emissions or lukewarm depends, among other things, on from the formation of the ingot (liquefied rocks) that then forms the lava. It also depends on additional factors, for example whether this alloy will come into contact with water on its way, says the professor. Iowa weak.

It started in Iceland on March 19 this year. A volcanic eruption at Fagradalsfjall Massif, about 40 km from Reykjavik. Since then, the lava flows quietly there from cracks in the ground. In turn, in Sicily in mid-December 2020, Mount Etna woke up; Dozens or so eruptions have already occurred, as lava sprang up and clouds of dust from the crater. After each stage of the awakening, it is necessary to sweep the streets and roads from the volcanic dust in the neighboring villages.

Why is the Icelandic volcano at Fagradalsfjall now quieter than the Sicilian Mount Etna? This was explained in an interview with PAP by geologist Professor M. Iwa Sui, Director of the Institute of Geosciences of the Polish Academy of Sciences and President of the European Union of Minerals.

“In order for a volcanic eruption to occur, a volcano must contain an alloy that is nothing but liquefied rock. The composition of this alloy determines what the eruption will look like” – says the professor. Weak.

The researcher explains that volatiles are a component of the alloy, which plays an important role in violent explosions. The mantle and crust may contain minerals that contain volatile groups, such as sulfur compounds, fluorine, chlorine, carbon dioxide, and hydroxide groups. When an alloy contains such components and has a high temperature, it is homogeneous, and these materials are incorporated into its structure. However, when the temperature drops, these substances are released in the form of more or less toxic gases. Its release from the alloy is accompanied by a rapid increase in pressure as the alloy rises to the surface and into the chimney of the volcano, splits into small fragments escaping from the volcano in the form of a massive cloud of dust and fragments of larger magma (these products from the volcanoes are called thermosets). The lava plume can reach several tens of kilometers in height.

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In most cases, volcanoes form at the surface separating tectonic plates. Whether these plates are pushing against each other or on the contrary, diverging, this is specifically related to the presence of volatile compounds, and thus the type of volcanoes and the nature of their eruptions.

Volcanic feet usually contain more volatile matter as tectonic plates compress each other. This is the case, for example, in Sicily, Mount Etna. That is why this volcano emits large quantities of ash and coarse fractions.

At the same time, volcanoes, which emit quietly lava, usually form in places where the continental or oceanic plates expand, and as a result of a long process, they break and separate in these places, and it should be noted that the oceanic plates – thinner – are more susceptible to these The process. We call it the rift process, “- says the professor. Weak. He explains that beneath the rift zone, especially the ocean, the Earth’s mantle, which does not contain much of the volatiles, is melting. The rift zone extends across the entire Atlantic Ocean, including Iceland. Hawaii is another site for continuous explosions of low volatile alloys. However, the genesis of these volcanoes is different, and has nothing to do with the rift.

For example, the most recent activity of the Icelandic volcano at Fagradalsfjall massif are fissures through which the ingot is ejected very softly. a. Bohr notes that the feet contain certain amounts of volatiles (so he advised residents of surrounding areas to close their windows). However, there are so few of them that a violent explosion could not occur in this environment.

Video: Live view of an eruption of an Icelandic volcano in the Fagradalsfjall mountain range

“In places where tectonic plates are stretched, volcanic eruptions are calm. However, they may be accompanied by additional conditions that could make these floods dangerous as well” – says the professor. Weak. “This was the case, for example, in Iceland in 2010, when Eyjafjallajokull volcano erupted, temporarily paralyzing air traffic in Europe. In this case, the problem was that the volcano was covered by an ice sheet. The ice was melted by temperature. The lava (about 1000 ° C), and the mixture of water and hot magma gave an incredibly powerful eruption effect. This water-melting reaction is called phreatomagmic. The ingot then violently shattered and turned into a dust cloud. The dust plume rose by about 12 km and encountered horizontal currents in The atmosphere spread the cloud over a large area of ​​Europe, which paralyzed air traffic. Ironically, the nearest airport in Reykjavik was not affected by this phenomenon “- describes Professor Siwi.

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He adds that the Icelanders were also anxious in 2014. Then the Bardaronga volcano woke up, which is partly under the glacier and has a very dynamic system of up to five chambers of magma at great depth. “A volcanic eruption would be so dangerous for the local population that not only would there be a strong emission of lava, dust and toxic gases, but also severe flooding. Fortunately, this volcano found a side outlet for its alloys and was quietly emitting without the glacier melting quickly. So it was There is a disaster, “- says the professor. Weak.

When a geologist was asked whether volcanic eruptions could be predicted, he explains: “No; at this stage in the development of science, we can identify and model the mechanisms that lead to the formation of the alloy, and predict its formation. We are also able to predict what kind of eruption it will have, with Taking into account the location of the volcano’s activity., We can predict what a lava flow or volcanic material flow (dust and coarse fractures) will look like and what their formation will look like, what are the morphologies, and what the structures are. We can also monitor the activity of magma chambers – recording increased revival or periods “Silence in them. He is able to predict a very accurate time for the eruptions themselves. However, using the knowledge gained from studying contemporary volcanoes, we can reconstruct the origin of the alloys and the course of their activity for the volcanoes millions of years ago.”

Therefore, it is not possible to accurately predict an eruption. The interviewee from PAP notes, for example, that the 2014 Japanese eruption of the Japanese Ontake volcano, which was a popular destination for weekend excursions, was a complete surprise. More than 60 people were killed then. “No one expected this day to come. It was a beautiful day and a large number of people went for a walk on its slopes. The cloud of dust that suddenly appeared made the people inside stop breathing” – he comments on that. It also gives an example of White Island near New Zealand. “The local Whakaari volcano was and still is a tourist attraction, and many companies have organized tours, picnics in the crater, and helicopter trips over the volcano there. In 2019, an unexpected violent eruption occurred and more than 20 people died. While monitoring the activity of this volcano, it was Volcanologists are aware of its increased activity, but it was impossible to predict the exact time of its eruption, ” – the researcher told PAP.

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There is no way to control volcanic activity. These are mighty powers, and humans are only able to increasingly recognize these phenomena without being able to control them. To a very limited extent, he can direct them a little “- he says. He only gives an example of the small actions that man can take – while indicating that this has nothing to do with the possibility of great control over the mighty forces of nature that lead to the formation of volcanic phenomena.

“Let’s go back to Mount Etna. During one of the volcanic eruptions, the inhabitants of a village near this volcano dug ditches to drain lava to prevent their homes from being destroyed. This action had a positive effect. However, please note what a small, large-scale stream means eruptions that could be That it emits millions of cubic meters of lava (for example Etna in 2018, 3-6 million cubic meters). This better illustrates the size of the phenomenon and our position as a human being, an observer, and a researcher of this type of phenomena, “- says the researcher.

PAP – Science in Poland, Ludwica Tomala

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