For more than 100,000 years, the Methana volcano in Greece appeared dormant. No lava, no explosions, no ash clouds. It appeared extinct – like many other volcanoes today. An international research team led by ETH Zurich has reconstructed a detailed, long-term history of the Methana volcano. Their conclusion is striking: While Methana appeared silent at the surface, enormous amounts of magma were steadily accumulating deep within its magma chambers.
To uncover the volcano’s hidden activity, researchers focused on tiny minerals called zircon. These crystals form inside magma reservoirs in the Earth’s crust, as the magma is cooling, and act like natural time capsules, preserving information about when and under what conditions they grew.
“We can think of zircon crystals as tiny flight recorders. By dating more than 1,250 of them across 700,000 years of volcanic history, we’ve reconstructed the volcano’s inner life with a precision and statistical power that simply wasn’t possible a decade ago,” explains Olivier Bachmann, senior author and professor of Volcanology and Magmatic Petrology, ETH Zurich. “What we learned is that volcanoes can ‘breathe’ underground for millennia without ever breaking the surface.”
The results of the study show that magma was produced almost continuously beneath Methana. While there were active phases with volcanic eruptions, there was also one exceptionally long quiet period of more than 100,000 years, during which no eruptions occurred at all. Crucially, this was exactly the geological timeframe when zircon growth peaked, showing clear evidence of intense magma activity.
The researchers report that the magma supplying Methana’s upper crustal chamber was very water-rich – far more so than they expected, particularly during the periods of dormancy. The mantle beneath Methana is strongly influenced by materials carried down by a subducting tectonic plate – including ocean-floor sediments and substantial amounts of water. This process “hydrates” the mantle and makes magma production especially efficient. As the magma rises through the crust, it becomes water-saturated and creates bubbles. Water saturation triggers crystallisation which thickens the magma and reduces its mobility. Using physical and thermodynamic models, the researchers show that such magma effectively slows itself down during ascent. Paradoxically, the more magma supply at the depth can lead to fewer eruptions because the magma is too water-rich and too crystalline to reach the surface.
“We actually believe that many subduction zone volcanoes might be periodically fed by particularly wet primitive magma, something that the scientific community has not yet fully recognized. These so-called ‘superhydrous’ melts might be much more prevalent in subduction-related volcanoes worldwide”. Lead author, Răzvan-Gabriel Popa, a volcanologist at ETH Zurich clarifies, “Methana is a great example where we have seen this effect clearly, but the impact of our findings can be generalized and widespread.”
The study’s most important and unsettling message is clear: A prolonged period of volcanic silence does not mean a volcano is extinct. Instead, it could signal the buildup of a large and potentially more dangerous magma system. This has major implications for volcanic risk assessment. Volcanoes that have not erupted for tens of thousands of years are often labelled extinct and receive little monitoring. Methana shows how risky that assumption can be – since a volcano can remain quiet for millennia while quietly storing energy for future reawakening.
“For volcano hazard authorities, for example, in Greece, Italy, Indonesia, Philippines, South and North America, Japan, etc. this means re-evaluating the threat level of volcanoes that have been quiet for tens of thousands of years but show periodic signs of magmatic unrest,” says Bachmann.
Modern monitoring tools, such as measurements of earthquakes, ground deformation, and gas emissions, as well as acquiring high-resolution images of the underground by geophysical methods, can help detect these hidden processes before they escalate.
Science Advances
Experimental study
Not applicable
A volcano reawakens after more than 100,000 years of “silent” magma reservoir growth
22-Apr-2026