Researchers from ETH Zurich and collaborators reconstructed ~700,000 years of volcanic history at Methana, a peninsula volcano in the Saronic Gulf. It’s part of the South Aegean Volcanic Arc, formed by the subduction of the African plate beneath the Aegean microplate.

The team reconstructed ~700,000 years of volcanic history at Methana (a peninsula volcano in the Saronic Gulf, ~50–60 km southwest of Athens, Greece) using detailed petrochronology — combining geochemistry, isotopes, and zircon U-Th/Pb geochronology. They analyzed data from over 1,250 zircon crystallization ages across 31 eruptive units.

Methana experienced multiple eruptive phases separated by long pauses. Its longest quiescence lasted >100,000 years (roughly 280,000–168,000 years ago). During this interval, there were no recognized surface eruptions, which might have led observers to classify the volcano as “extinct” or fully dead.

Olivier Bachmann (ETH Zurich) noted that this means reassessing threat levels for volcanoes quiet for tens of thousands of years but with periodic magmatic signals.

“Quiet doesn’t always mean safe.”

“Extinct” is a human label based on surface behavior, but magmatic systems operate on much longer timescales. A volcano that has been quiet for millennia may simply be in a “silent growth” phase — still very much alive beneath the surface.

This doesn’t mean panic for Methana or similar volcanoes, but it does mean greater caution in how we define and monitor volcanic risk globally. Long dormancy can be misleading comfort.

However, zircon crystallization (a proxy for active magma presence, cooling, and differentiation in the crust) did not stop. It actually peaked during this long quiet period. This indicates that magma production continued vigorously in the mantle and upper crust, with substantial magma accumulation and reservoir growth happening silently underground.

The magma involved was unusually water-rich (superhydrous). High water content causes early crystallization as the magma rises and cools/depressurizes, making it more viscous and “sticky.” This traps it in the crust instead of letting it ascend easily to erupt. The result: the volcano “breathes” quietly, building a larger reservoir over tens of thousands of years without visible activity.

Eventually, after this “silent growth” phase, the system reactivated with new eruptions. The study suggests this mechanism explains why some volcanoes can appear dead for very long periods but still pose future hazards.

Popa and team describe the volcano as the visible “tip of the iceberg,” while most of the igneous system evolves hidden below. This mechanism explains extended quiescence without the system dying.

Re-evaluating “extinct” volcanoes: A long dormancy (even >10,000–100,000 years) does not reliably mean a volcano is dead. It can instead signal a maturing system building a larger reservoir that could later produce more significant activity.

Transition potential: Such silent growth may allow small stratovolcanoes to evolve toward larger, more hazardous systems (including caldera-forming ones) by accumulating substantial magma volumes over time.

Hazard monitoring: For Methana and similar subduction-arc volcanoes (e.g., others in the South Aegean Volcanic Arc like Santorini), scientists need sensitive geophysical and geochemical tools to detect deep reservoir changes, not just surface unrest. Methana itself is still considered active (last eruptions in the Holocene, a few thousand years ago), but it is not currently showing signs of imminent threat.

The study emphasizes that this process is likely widespread in subduction zones where water-rich magmas are common.

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A volcano reawakens after more than 100,000 years of “silent” magma reservoir growth

That’s the title of the open-access paper published on April 22, 2026, in Science Advances by Răzvan-Gabriel Popa and colleagues (including Olivier Bachmann) from ETH Zurich and collaborators.

Journal: Science Advances, Vol 12, Issue 17

DOI: 10.1126/sciadv.aec9565

Article Title: A volcano reawakens after more than 100,000 years of “silent” magma reservoir growth

Article Publication Date: 22-Apr-2026

Authors: Răzvan-Gabriel Popa, Olivier Bachmann, Marcel Guillong and Andrea Giuliani

Abstract

Magmatic systems can remain dormant for tens of thousands of years, creating a misleading perception of extinction that complicates hazard forecasting. To identify drivers of protracted quiescence, we integrate geochemical, isotopic, and zircon geochronological data comprising over 1250 crystallization ages from 31 eruptions at Methana, an active volcano near Athens, Greece. This record allows us to link eruptive activity, magma reservoir evolution, and mantle source variations over 700,000 years. Here, extended repose correlates with increased metasomatism of the mantle wedge by slab-derived components. The longest quiescence at Methana (>100,000 years) coincides with substantial magma production that was preferentially trapped in the crust. We attribute this trapping to the generation of superhydrous melts (>6 wt % H₂O) from a highly metasomatized mantle. These volatile-rich magmas undergo water saturation and crystallize during ascent, preventing eruption. Such trapping mechanisms can grow large magma reservoirs and may enable transitions from small stratovolcanoes to highly hazardous, caldera-forming systems.