Stromboli's Eruptions Reveal a Pattern in the Last 140 Years

Italy's Stromboli volcano has remained active with low activity, allowing scientists to study its behavior. A recent study published in the Nature journal Scientific Reports, an analysis of Strombolian activity was done by scientists from Italy's National Institute of Geophysics and Volcanology (INGV) and the University of Bristol.

Occasionally, the volcano has sudden explosions that are more intense than usual, like what happened this July. Also known as Strombolian paroxysms, some of the volcano's craters are simultaneously active, resulting in major explosions.

The team cataloged Stromboli's volcanic activity for the last 140 years, discovering that 36 out of 140 explosions were paroxysms. Historical records were then used to estimate how frequent larger paroxysms occurred and if there is evidence of eruption memory or the relationship between two paroxysmal eruptions.

Patterns of Strombolian Paroxysmal Eruptions

Massimo Pompilio from INGV said that the catalog they created made it possible for the researchers to classify Stromboli's explosions. In the past decade, there was about one paroxysm every four years. During the 1940s, the major explosions were more frequent.

Stromboli "alternates between periods of intense activity and periods of relative quiet," said Pompilio. For example, the 56-day gap between two major explosions in 2019 was not rare. There were also four periods that a gap between paroxysms lasted up to 15 years. Between 1959 and 2003, there were no recorded paroxysms.

The catalog of past explosions can help researchers forecast future activity and possibilities of paroxysms. Andrea Bevilacqua explained that volcanic explosions occurring at irregular intervals are studied at inter-event times. "In particular, the development of inter-event models allows us to calculate the probability of an explosion occurring as a function of the time elapsed since the last event of that type".

Currently, there is a 50% chance that a paroxysm will occur a year after the last explosion. There is also a 20% chance that a Stromboli paroxysm will occur less than two months after and a 10% chance that no major explosion will occur in the next ten years.

Predicting Future Volcanic Eruptions

The data proves that the volcano's explosions are not random events, said Augusto Neri. For the statisticians, the repetitive sequences are memory processes. The next scientific challenges include understanding the reasons and physical mechanisms of the volcanic memory processes.

Forecasting future paroxysmal activity can also help determine how likely major explosions will occur and associated risks. With volcano tourism growth in recent years, said Professor Willy Aspinall from Bristol, it is important to predict eruptions to keep tourists safe and avoid the White Island/Whakaari volcano incident in New Zealand last year.

Understanding how specific volcanoes have eruption memory could help "inform decisions about volcanological fieldwork at the craters,' said Aspinall. For now, more research is still needed to determine how to keep people safe from unexpected volcanic explosions.

Check out more news and information on Volcanoes on Science Times.