Santorini Hides Largest Eruption in 765,000 Years
Research drilling reveals a 150-meter pumice layer and nineteen previously undocumented eruptions at the nearby Kolumbo volcano.
Updated on Nov. 6, 2026 in Geology
Research drilling under the international Ocean Discovery Program uncovered a previously unknown pumice layer up to 150 meters thick beneath Santorini, recording the island's largest known eruption 765,000 years ago. Researchers also identified at least 19 previously undocumented eruptions at the submarine Kolumbo volcano over the past 265,000 years.
Why it matters
The findings reshape the known eruption history of an interconnected volcanic-tectonic system spanning Santorini, Kolumbo and Amorgos. The record shows the region has produced eruptions far larger than the Minoan event, informing how scientists assess future hazards.
The pumice layer reaches up to 150 meters thick and records the 765,000-year-old eruption, while drilling identified at least 19 previously undocumented Kolumbo eruptions over 265,000 years. Hydrothermal changes and unstable crater slopes could trigger cascading hazards even without magma reaching the surface.
The players
Ocean Discovery Program
An international scientific drilling program that funded the research drilling beneath Santorini and surrounding waters.
The details
Drilling was conducted under the international Ocean Discovery Program, which uncovered the pumice layer beneath Santorini. The 726 AD eruption at Kameni released approximately one cubic kilometer of magma, and magma remained trapped deep underground during the 2025 seismic crisis, which has fully subsided.
Timeline
765,000 years ago: Santorini's largest known eruption
726 AD: Kameni eruption releases about one cubic kilometer of magma
Past 265,000 years: At least 19 undocumented Kolumbo eruptions identified
2025: Seismic crisis at Santorini, now fully subsided
The Big Picture
The discovery shifts the scientific understanding of the Santorini-Kolumbo-Amorgos system, which the Ocean Discovery Program's drilling has now shown to be interconnected. It challenges assumptions built on the Minoan eruption as the defining benchmark for the region's volcanic hazard.
Scientists may use the eruption record to refine hazard assessments for islands in the region. Understanding that hydrothermal changes and crater instability can cascade without magma reaching the surface could guide future monitoring priorities.
The takeaway
The region's volcanic history extends far deeper than the Minoan eruption, so hazard planning should account for the full record. Monitoring should watch for hydrothermal and slope changes, not only magma movement.
Further reading
Explore more in Geology for context on how volcanic records like these are built.
Source note: This article includes information reported by Ekathimerini.
