Mount Etna: New Insights into Europe's Most Active Volcano

Mount Etna, a stratovolcano in Sicily approximately 500,000 years old, is Europe's most active volcano, producing several eruptions per year. Two recent studies have provided new insights into the volcano's magma generation and eruption dynamics.

Magma Source and Generation

A study published in the Journal of Geophysical Research: Solid Earth proposes that the source of Mount Etna's magma differs from that of most stratovolcanoes.

"Etna's magma source is analogous to that of petit-spot submarine volcanoes—typically small, rising only a few hundred meters—making Etna's scale unusual."

Key findings from this study include:

• Etna releases alkaline lavas at a higher rate than expected, given the typical time required to produce such magma.
• Analysis of lava samples from the past 500,000 years shows consistent chemical composition despite tectonic changes.
• The research proposes that Etna's magma source is analogous to that of petit-spot submarine volcanoes, first identified in 2006.
• The proposed mechanism involves magma trapped between the upper mantle and tectonic plates approximately 80 km below the surface. This magma is released through cracks resulting from the subduction of the African Plate under the Eurasian Plate.

The research was led by Sébastien Pilet, a geoscientist at the University of Lausanne.

Eruption Dynamics

A separate study, led by Cornell University and published in Geochemistry, Geophysics, Geosystems on June 2, examined the different mechanisms behind two historic eruptions.

The two eruptions studied were:

• The 122 B.C. Plinian eruption
• The Fall Stratified event, which occurred approximately 4,000 years ago

"The research shows that both water and carbon dioxide can drive explosive eruptions, with CO₂ causing eruptions that originate deeper and occur faster, while water controls shallower processes."

Key findings from this study include:

• The 122 B.C. eruption involved magma originating from a depth of approximately 22 km. The magma paused at a depth of 2–5 km for weeks, releasing gas gradually before erupting.
• The Fall Stratified event involved magma rising quickly from a depth of 24–30 km. This eruption occurred within hours and was driven by a higher concentration of carbon dioxide (CO₂).

Methodology:

The researchers used Raman spectroscopy to measure the density of CO₂ in micron-sized bubbles within magma crystals. They converted this density measurement to pressure, and then to depth. Field samples were collected by collaborators from Columbia University and the University of Hawaii.

Implications:

According to the study, understanding these dynamics aids in volcanic risk assessment. The method is being applied to volcanoes in Chile, Hawaii, and other locations. The study was led by Maxim Gavrilenko and Esteban Gazel (Cornell University).