A newly discovered method of monitoring magma movements under Mount Etna could help scientists predict when a volcano might erupt.
Mount Etna, located on the Italian island of Sicily, is the largest active volcano in Europe. Humans have documented its activity over the past 2,700 years, but the volcano’s eruptive history extends It dates back 500,000 years.
The new method could make it easier to predict Mount Etna’s eruptions. In a new study, researchers at the Italian National Institute of Geophysics and Volcanology (INGV) analyzed a parameter called the b-value, which describes the ratio of low-magnitude earthquakes to high-magnitude earthquakes in a region of the Earth’s crust. This ratio can change as magma rises through the crust to the top of the volcano, the researchers reported in a study published October 8 in the journal. Advancement of science.
“Changes in the b value over time reflect how pressure evolves inside the volcano,” said the study’s lead author Marco Ferretto CarlinoThe geophysicist at INGV’s Etna Observatory told Live Science in an email. “Since the rise of magma leads to changes in pressure within the crust, tracking the b value can help reveal the different stages of magma transition from depth to the surface.”
The b value is an established parameter in volcanology, but the researchers examined it in a new way, using an updated statistical model. By collecting 20 years of seismic data from Mount Etna, they found a “very strong” relationship between the b value and Etna’s volcanic activity, Ferrito Carlino said.
Mount Etna is located in the collision zone between the African and European tectonic plates. As a result, a vertical fracture in the Earth’s crust known as a strike-slip fault lies beneath the fault volcanoThis facilitates the rise of magma to the surface, according to the study.
The crust beneath Mount Etna is up to 19 miles (30 km) thick. Magma rises through this volume before erupting, but instead of replenishing a single magma chamber, the molten rock feeds a series of interconnected storage areas located in the crust at different depths.
The deepest magma storage area is 7 miles (11 km) below sea level, and it feeds an intermediate storage system with different zones that likely extend 2 to 4 miles (3 to 7 km), Ferrito Carlino explained. As the magma rises, it travels through a complex network of fissures and eventually reaches the final storage area, which is located above sea level within the volcanic edifice.
The researchers had a wealth of data to work with and extract b values from, due to Etna’s frequent activity. They analyzed seismic patterns in 19 miles of crust beneath the volcano from 2005 to 2024, paying particular attention to how these patterns vary between regions of the Earth’s crust.
In general, regions of the Earth’s crust that contain active magma storage areas show higher b values than more stable regions, because active regions are exposed to smaller volumes Earthquakes Of the bigger ones.
“This happens because rocks affected by the moving magma become weak and severely fractured,” Ferrito-Carlino said. “For example, when magma inside a reservoir releases volatiles, it permeates the surrounding rock, facilitating the sliding of small fractures.”
Conversely, areas of the Earth’s crust that are more stable typically experience larger earthquakes more than smaller ones, because breaking rocks requires greater force. “Rocks with good mechanical properties can store pressure for longer periods,” Ferrito-Carlino said. “When they finally break, they produce larger earthquakes, corresponding to lower b values.”
Therefore, by tracking the b value over time, it may be possible for researchers to follow the movement of magma through the deep crust to the first storage area, from there to the intermediate storage system, and again to the shallow storage area. This method could help experts estimate the timing of eruptions on Mount Etna.
“Monitoring the b value provides a powerful way to track the movement of magma within the crust and assess the state of volcano development before eruptions,” Ferrito-Carlino said.
Mount Etna was a good testbed for the study due to its layered magma storage areas and massive earthquake catalog, but the findings may also apply elsewhere.
“In principle, the b value could also be used to track magma movements in other volcanic regions, provided that a sufficient number of earthquakes are available and that their locations are distributed over different crustal sectors, well constrained by previous geological studies,” Ferrito-Carlino said.