Scientists from ETH Zurich have revealed that the Methana volcano in Greece, long considered dormant, has maintained active magma reservoirs for over 100,000 years without surface eruptions. The study, published in Science Advances, indicates that the volcano located near Athens remains geologically active despite its last recorded eruption occurring in 250 BCE.

Researchers analyzed more than 1,250 zircon crystals from ancient volcanic rock to track geological processes through radioactive uranium degradation. The data confirmed that zircon formation and magma movement continued during periods of surface silence, proving that the volcanic system was accumulating magma in deep chambers rather than entering a state of extinction.

The study attributes the lack of surface activity to the specific composition of the magma, which is exceptionally water-rich. As this magma rises, decreasing pressure causes gas bubbles to form, increasing its viscosity and trapping it beneath the Earth's surface. This process creates underground reservoirs that do not immediately result in volcanic events.

These findings challenge the traditional geological definition of extinct volcanoes, which typically applies to those without eruptions for 10,000 years. The research suggests that periods of dormancy lasting up to 100,000 years do not guarantee a volcano is no longer a potential threat.

Geologists will now reassess monitoring protocols for other volcanoes currently classified as extinct. Further studies are expected to determine the specific triggers that could cause these trapped magma chambers to reach the surface.