The terrible scenes of the eruption of the Honga Tonga volcano (500 times more powerful than the atomic bomb of Hiroshima) have brought back all the widespread fears about similar eruptions also in Italy. Leaving aside the volcano most similar to Honga Tonga, that Marsili that "lies" just below the surface of the water, the suspect number one (I am not saying this because of Naples) is Vesuvius.
Vesuvius is a very dangerous volcano. It is the only volcano in Europe classified as a decadal volcano, meaning it has the potential to produce a major eruption within 10 years. The last time Mount Vesuvius erupted was in 1944, and the resulting ash and pumice caused considerable destruction in the area. If Vesuvius were to erupt again now, the consequences could be catastrophic.
History has shown us how dangerous the eruptions of Vesuvius can be, prompting us to think about a possible method of prevention.
The expert researchers of volcanoes of the ETH in Zurich have started a new study, dedicated precisely to the analysis of the volcano's eruptions and its history. The main objective is to develop a theory on a possible new explosion.
The previous episodes, which occurred both in historical times and prehistoric, they brought explosive eruptions capable of destroying entire countries. The people settled nearby have had no chance to save themselves, and the consequences have been catastrophic.
To try to predict the arrival of the new one eruption, researchers from Zurich examined the four largest eruptions of Vesuvius, which occurred in the past 10.000 years.
In particular, they considered: the Avellino eruption of 3.950 years ago; the eruption of 79 AD that buried the Roman cities of Pompeii and Herculaneum (also known as the “Plinian eruptions”); the sub-Plinian eruption of 472 AD and the eruption of 8890 BC
Garnets in the magma of Vesuvius
The first elements analyzed, taken into consideration to differentiate the different eruptions, are the garnet crystals present in the volcanic deposits
“Garnet” is a unique material of its kind, a mineral that grows from magma when the latter remains stuck in the magma chamber. Knowing the age of the crystals helps establish how long the magma remained in the chamber before Vesuvius erupted.
In their study, published in the journal Science Advances , the researchers explained the analysis mechanisms of garnet.
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To determine the age of crystals, materials such as uranium and thorium were used.
Garnet has a structure that incorporates small amounts of the materials, which can then be measured by experts. Using the ratio of the isotopes uranium-238 to thorium-230, researchers can calculate the crystallization age of minerals.
The garnets taken into consideration for the development of this study come from the set of materials collected by the ETH team directly "on site".
To ensure the highest level of precision, the sites corresponding to the four explosions – the places where debris can still be found – were chosen for each extraction.
The age of granite crystals
By developing the research and analyzes described above, the researchers were able to understand the mechanism behind the explosion.
They understood that the most explosive magma in Vesuvius (the magma called "phonolytic”) is stored in a reservoir in the upper crust for several thousand years before the influx of hotter magma (the so-called “ magmaprimitive“), who is responsible for the explosion.
Apparently, in the two prehistoric events the magma remained in the chamber for about 5.000 years. In historical ones, time has shrunk to around 1.000 years.
All this happens because, as the project manager reminds us Olivier Bachmann, “Vesuvius has a rather complicated hydraulic system.”
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Under the volcano there are several magma chambers connected by a system of pipes.
The upper chamber – responsible for the eruptions – fills with magma coming from one of the lower chambers. Here, the material crystallizes, activating a process called “magmatic differentiation”. At this point, the "differentiated" magma is called phonolite.
After a certain amount of time, the more primitive or "mafic" magma flows into the upper chamber, generating an increase in pressure inside the chamber. All this pressure pushes the phonolitic magma upward, potentially all the way to the surface, starting an eruption.
A reserve of phonolitic magma is currently preserved under Vesuvius. Experts wonder how much more remains, and whether the next eruption will be catastrophic or "manageable."
Vesuvius next eruption: is it possible to predict it?
A new statistical model that examines periods of high and low eruptive activity allows us to compare the probability of eruption and the danger of Vesuvius, the Ischia area and the Campi Flegrei. This understanding can help improve our knowledge of their behavior.
An international team of researchers fromNational Institute of Geophysics and Volcanology (Ingv),University of Bari Aldo Moro and British geological survey (bgs) of Edinburgh (United Kingdom) published the study “a Simple two-state model interprets temporal modulations in eruptive activity and enhances multivolcano hazard quantification” in Science Advances. The aim of the study was to analyze three active volcanoes. I link it to you here.
The publication of this new study helps improve our scientific understanding of volcanic activity, which is essential for making predictions and taking measures to protect people and infrastructure in risk areas.
When and how will it be?
Currently, it is not possible to determine the amount of magma, both phonolithic and mafic, preserved in the depths of Vesuvius. However, as the volcano has been producing mainly mafic magma since 1631, researchers believe it is unlikely that differentiated phonolite is currently accumulating.
The hypothesis of a disastrous explosion like the one that destroyed Pompeii and Herculaneum is quite unlikely. The volcano requires a much longer period of quiescence to reach similar levels. “We think it is more likely that a large, explosive eruption of Vesuvius will occur only after a period of dormancy lasting centuries.” Bachmann revealed.
“However, smaller but still very dangerous eruptions like the one in 1944 or even the one in 1631 can occur after shorter periods of quiescence. An accurate prediction of the size and style of volcanic eruptions is so far not possible. However, awakening magma reservoirs beneath volcanoes are now recognizable by monitoring.”
To better apply the data to the model created, and safeguard the citizens who live near Vesuvius, the volcano will be monitored 24 hours a day. In addition, an emergency plan has been prepared for possible evacuation, so as to protect as many people as possible. .
