A recent study focusing on the sampling and examination of volcanic ash from the Cumbre Vieja volcano in the Canary Islands, situated off the northwest coast of Africa, indicates that the type of magma can influence tremors during volcanic eruptions. The research emphasizes the usefulness of volcanic ash analysis in monitoring and predicting eruptions.
A recent study focusing on the sampling and examination of volcanic ash from the Cumbre Vieja volcano in the Canary Islands, situated off the northwest coast of Africa, indicates that the type of magma can influence tremors during volcanic eruptions. The research, published today in the journal Nature Geoscience and led by scientists from the American Museum of Natural History and the City University of New York (CUNY), underscores the significance of analyzing volcanic ash as a method for monitoring and forecasting eruptions.
“In recent years, the volcano research community has significantly improved its ability to predict when a volcanic eruption might begin, but forecasting the nature and length of these eruptions remains challenging,” stated study co-author Samantha Tramontano, a Kathryn W. Davis Postdoctoral Fellow at the Museum. “If our findings apply to other volcanoes, we could potentially monitor the internal properties of magma during eruptions from the surface, which would be crucial for assessing hazards.”
In September 2021, following 50 years of dormancy, the Cumbre Vieja volcano on La Palma island in Spain’s Canary Islands erupted, leading to the evacuation of thousands. Over the next 85 days, the eruption destroyed over 3,000 structures and vast areas of farmland. Tramontano and her then-advisor at CUNY, Marc-Antoine Longpré, established a system to collect nearly daily samples of ashfall throughout the three-month eruption, collaborating with colleagues from the Instituto Volcanológico de Canarias and the Instituto Geográfico Nacional.
The collected samples represented 94 percent of the eruption’s duration and were sent to the Museum for chemical analysis of the glass contained within the ash, which originated from rapidly cooled magma ejected from the volcano. This was accomplished using an electron microprobe, producing a continuous daily dataset of the liquid composition of the magma, a first in its field.
The study unveiled fluctuations in the silica content of the samples, a substance that contributes to the viscosity of magma. Higher viscosity in magma typically corresponds with more explosive eruptions. Researchers discovered that silica levels were elevated during the first week of the eruption but declined steadily until a notable increase occurred two weeks prior to the end, likely signaling the depletion of magma supplies from the mantle.
The research team correlated this chemical data with physical observations gathered simultaneously, finding a link between silica levels and the intensity of volcanic tremors—seismic vibrations linked to the movement of liquids and gases under the volcano’s surface. Through modeling and additional analysis, the team suggests that more viscous magma with higher silica content correlates with greater volcanic tremor strength, although further research is necessary to validate this mechanism.
Beyond shedding light on the origins of volcanic tremors, a critical parameter for eruption monitoring, this study highlights the advantages of integrating petrological data collection, such as ashfall, with geophysical measurements to enhance eruption forecasting, hazard evaluations, and decision-making processes during volcanic emergencies.
“A significant challenge in petrological monitoring is organizing fieldwork and sample transfers during eruption events to facilitate rapid analysis,” explained Longpré. “With careful planning and advancements in technology, it should become feasible to conduct efficient, near-site sample analyses in the future, thereby aiding the prompt interpretation of geophysical data.”
