CO2 and Water Drove Mount Etna's Historic Eruptions

A new study led by Cornell University has revealed that carbon dioxide and water played crucial roles in two historic eruptions of Mount Etna in Italy, offering insights that could help assess volcanic risks worldwide. The research, published June 2 in Geochemistry, Geophysics, Geosystems, used a novel technique involving Raman spectroscopy to analyze tiny bubbles trapped in magma crystals, measuring their density to reconstruct the volcano's plumbing system with unprecedented precision.

The team, led by Esteban Gazel, found that the 122 B.C. eruption, one of the most explosive on record, involved magma rising slowly from about 22 kilometers depth, pausing at 2 to 5 kilometers for weeks to release gas before erupting.

In contrast, a much older eruption known as the Fall Stratified event, nearly 4,000 years ago, saw magma rise quickly from 24 to 30 kilometers deep, propelled by high CO2 concentrations, erupting within hours. Mount Etna is unique among volcanoes in that both water and CO2 compete to control eruptions, with higher CO2 thresholds leading to deep, fast eruptions and higher water thresholds controlling shallow processes.

The method is now being applied to volcanoes in Chile, Hawaii, and other locations, with the goal of improving physical models for risk assessment.