The Etna, located in Sicily, is the most active volcano in Europe and a natural laboratory for understanding the mechanisms that trigger the most violent eruptions.
A study led by Cornell University, with participation from Columbia University and University of Hawaii, analyzed two explosive episodes separated by thousands of years and revealed how variations in magma gases —water and carbon dioxide— can determine whether an eruption occurs within hours or after weeks of retention.
Two eruptive styles in the same volcano
- Plinian Eruption of 122 B.C.: the magma ascended from 22 km depth and was retained between 2 and 5 km below the surface for weeks. The slow escape of gases and the formation of crystals made the magma more viscous, accumulating pressure until generating a sudden explosion that launched ash more than 26 km high and covered 530 km² of Sicily.
- Fall Stratified Event: occurred 4,000 years ago, the magma remained at greater depth (24-30 km) with high levels of CO₂. The gas pressure caused a rapid ascent at 17.5 m/s and an explosive eruption in a few hours, without a surface retention phase.
The role of gases
Professor Esteban Gazel explained that Etna is one of the few volcanoes where water and carbon dioxide compete to control the eruption:
- When CO₂ predominates, the explosion occurs quickly and from great depth.
- When water predominates, the process slows down and concentrates at levels near the surface.
These findings show that the same volcano can produce very different eruptions depending on the gaseous composition of the magma.
State-of-the-art techniques
The study used advanced methods to analyze microscopic bubbles trapped in olivine crystals:
- Raman Spectroscopy: allowed measuring the density of CO₂ and calculating the pressure and depth of the magma before the eruption.
- Magmatic inclusions: small pockets within crystals containing remnants of molten rock or gas, key to reconstructing the history of the magma.
- Physical and chemical models: estimated the original amount of water and CO₂ and the storage conditions in the Earth’s crust.
Implications for volcanic prediction
Understanding how gases influence the explosiveness of Etna has direct consequences for the assessment of volcanic risks:
- Improves early warning systems in populated regions.
- Allows creating more accurate models to anticipate eruptions in other active volcanoes.
- These techniques are already being applied in volcanoes in Chile, Hawaii, and other countries, with the aim of building global prediction models.
The study demonstrates that the explosiveness of Etna depends on both the water and carbon dioxide present in the magma. This duality explains why the same volcano can generate slow, retained eruptions or rapid, deep explosions.
The research not only provides key information about Sicily but also opens the door to improving preparedness for volcanic risks worldwide.
