Knowing how to distinguish the differences between dormant volcanoes and permanently extinct volcanoes is crucial for the safety of populations. When a crater remains silent for tens of thousands of years, vigilance inevitably drops, vegetation regains its rights and cities are established at its feet. It is precisely this feeling of security that an international team of researchers has just shaken up by looking into the case of Methana, a volcanic peninsula located in Greece.
On the surface, Methana today is a peaceful place, best known for its hot springs and picturesque landscapes, but beneath the surface the story is quite different. To uncover the secrets of this sleeping giant, scientists delved into the volcano’s most distant past by analyzing tiny crystals called zircons, released during ancient eruptions.
These crystals function like real geological black boxes. As they cool in the Earth’s core, they trap the exact conditions that existed in the magma chamber when they formed. Researchers from the Swiss Federal Institute of Technology in Zurich (ETH) have achieved the feat of analyzing more than 1,250 of these crystals, thus reconstructing the internal activity of the volcano over a dizzying period of 700,000 years.
The results of this survey, relayed by IFL Science, are surprising. Analyzes prove that Methana went through a period of apparent sleep for more than 100,000 years. However, during this very long silence, the volcano was absolutely not dead. On the contrary, it continued to accumulate large quantities of magma in an immense underground reservoir, well hidden in the shadow of the earth’s crust.
The mystery of magma that “breathes” in silence
“What we learned is that volcanoes can breathe underground for millennia without ever breaking through the surface»explains Olivier Bachmann, lead author of the study. This invisible breathing means that the absence of an external eruption does not guarantee the end of the danger. But then, why has this overflowing tank not exploded yet? The answer lies in the chemical composition of the molten rock.
The zircons revealed that the magma trapped beneath Methana contained a much greater amount of water than previously thought. However, a waterlogged magma changes its behavior, it becomes thicker, viscous, and crystallizes quickly. By becoming slimy in this way, it struggles to rise to the surface and remains stuck in the depths. It is this physical phenomenon which saved the region from a major catastrophe, even if the risk of a sudden awakening is not excluded today.
This study radically changes the situation for global volcanological monitoring. Highly exposed countries such as Italy, Indonesia, Japan and the Philippines are home to dozens of structures considered inactive or extinct since the dawn of time. For security authorities, the message could not be clearer: we will have to reassess the threat level of these forgotten sites as soon as they show the slightest sign of magmatic unrest.
A dormant volcano – even for millennia – is therefore not dead. Thanks to these small zircon crystals, science now has a new parameter to monitor closely in order to avoid a potential catastrophe.
