A change in the composition of gases emitted from a volcano can signal a major volcanic eruption. Some volcanoes erupt without any warning signs and speculating the exact time a dormant volcano would erupt is difficult, hence, this observation will warn scientists days or months before an eruption, preventing casualties in the process.
The study, published in the journal Nature Geoscience, involved analysing trapped apatite, minute mineral crystals that have been emitted from the Campi Flegrei volcano found near Naples in southern Italy, which last erupted in 1538 but has been showing signs of unrest lately.
Scientists from the universities of Oxford and Durham in the UK in collaboration with the team from the Vesuvius Volcano Observatory in Italy, explain that the apatite crystals are “time capsules.” They reveal that the magma has been in a bubble-free state and only becomes filled with bubbles, consisting of fluorine, chlorine and water inclusions, shortly before an eruption.
Experts used to think that the eruptions were caused by the pressure from the accumulation of bubbly, gas-saturated magma over centuries. However, this study proves that some eruptions may be triggered even if gas bubbles only formed within days to months.
So earthquakes and ground deformation seen at the surface may not necessarily be signs of an imminent eruption under these conditions. Instead, these signs only indicate the arrival of new magma batches below.
‘We have shown for the first time that processes that occur very late in magma chamber development can trigger explosive eruptions, perhaps in only a few days to months,” adds lead author Mike Stock, from the Department of Earth Sciences at the University of Oxford. “This has significant implications for the way we monitor active and dormant volcanoes, suggesting that the signals we previously thought indicative of pre-eruptive activity – such as seismic activity or ground deformation – may in fact show the extension of a dormant period between eruptions.”
“Now that we have demonstrated that this approach can work on a particular volcano, and given apatite is a mineral found in many volcanic systems, it is likely to stimulate interest in other volcanoes to see whether there is a similar pattern,” asserts co-author David Pyle from the Department of Earth Sciences at the University of Oxford. “This research will also help us refine our ideas of what we want to measure in our volcanoes and how we interpret the long-term monitoring signals traditionally used by observers.”