Mount Etna Is a Rare Fourth-Category 'Petit-Spot' Volcano
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- University of Lausanne researchers published a study in the Journal of Geophysical Research—Solid Earth proposing that Mount Etna is fed by magma pockets 80 kilometers deep in the upper mantle, not by conventional subduction or hotspot processes.
- Mount Etna fits none of the three standard volcano formation models (plate boundaries, subduction zones, hotspots), despite its chemical composition resembling hotspot volcanoes—prompting researchers to invoke a 'petit-spot' mechanism first described by Japanese geologists in 2006.
- Lead author Sébastien Pilet said the finding is unexpected because petit-spot processes had previously only been documented in tiny submarine volcanic structures rising a few hundred meters, while Etna is a 3,000+ meter stratovolcano active for roughly 500,000 years.
- The African-Eurasian plate collision drives sporadic magma transport toward the surface through fractures in the bending tectonic plate, likened by researchers to 'liquid being squeezed from a sponge.'
- Etna's magma composition has remained largely consistent over 500,000 years even as the tectonic regime evolved, supporting the idea that the magmas pre-exist in the upper mantle and that eruption volume is controlled by plate movements.
- The study, done in collaboration with Anna Rosa Corsaro of Italy's Istituto Nazionale di Geofisica e Vulcanologia in Catania, could improve volcanic hazard assessment for Europe's most active volcano.
Why it matters: Mount Etna erupts several times a year near populated areas of Sicily, and its behavior has never fit any standard volcanic model. Identifying it as a petit-spot volcano—fed by 80-km-deep mantle magma pushed up by the African-Eurasian plate collision—gives INGV researchers a new framework for hazard assessment of a volcano that has long defied prediction.
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