The temporal distribution of volcanic eruptions of different scales and magnitudes on Earth has been revealed. The results of the research, conducted by INGV, have been published in Nature Scientific Reports
The research, Global time-size distribution of volcanic eruptions on Earth, by the National Institute of Geophysics and Volcanology (INGV), describes the return times and the frequency of eruptions of different scales, from small and frequent to rare ones and catastrophic, and suggests that its size and impact cannot be predicted with certainty. Volcanic eruptions are among the most spectacular events on our planet. With an average frequency of about 40 per year, they can vary from peaceful lava flows along the sides of the volcano, up to fortunately rare events capable of modifying the earth's climate and, in extreme cases, never observed in historical times, trigger devastating consequences.
The study integrates the methods of statistical analysis with the recent compilation of worldwide databases for the last million years. The results were published in Nature Scientific Reports (https://www.nature.com/articles/s41598-018-25286-y).
"By analyzing the data", says Paolo Papale, INGV research manager of the Pisa Section and author of the publication, "we understood that explosive eruptions, from the smallest ones which occur on average 4-5 times a year up to the cyclopean ones of which we know 27 cases over the last two million years (the last occurred in New Zealand about twenty-seven thousand years ago), occur on the planet's scale with a frequency distributed according to a power law. In other words, a rash tends to be ten times rarer when its size is ten times larger. The situation is analogous to that of a pile of sand: as we add sand to the top, landslides of material occur whose dimensions are distributed according to a power law.
For this category of events, the occurrence of a certain size depends on a very high number of variables that interact with each other in such a complex way as to preclude any possible control or certain forecast, regardless of how refined the knowledge of the system is.
“Today we are able to carry out numerical simulations of the processes that occur from the depths of magmatic systems up to the dispersion of volcanic products in the atmosphere and we constantly measure a large number of parameters that warn us of even minimal variations in the state of an active volcano. All this allows us to prepare for the occurrence of a new eruption. However", observes Papale, "a reliable method has never been produced worldwide to predict, on the basis of these measurements, the magnitude of the eruption that will follow".
The results of the research suggest that this limit may constitute a fundamental characteristic of explosive eruptions and therefore it may not be possible, even in the future, to make certain predictions on the size and impact of a future eruption.
“For this reason”, concludes Papale, “in our hazard assessments we refer to different possible eruptive scales, each associated with a different probability. Research in the field of volcanic hazard therefore focuses on how to transfer increasingly in-depth knowledge into more reliable probabilistic assessments that can allow the authorities to better manage volcanic risk".
Extended
Global time-size distribution of volcanic eruptions on Earth
Paul Papal.
Volcanic eruptions differ enormously in their size and impacts, ranging from quiet lava flow effusions along the volcano flanks to colossal events with the potential to affect our entire civilization. Knowledge of the time and size distribution of volcanic eruptions is of obvious relevance for understanding the dynamics and behavior of the Earth system, as well as for defining global volcanic risk. From the analysis of recent global databases of volcanic eruptions extending back to more than 2 million years, I show here that the return times of eruptions with similar magnitude follow an exponential distribution. The associated relative frequency of eruptions with different magnitude displays a power law, scale-invariant distribution over at least six orders of magnitude. These results suggest that similar mechanisms tend to explosive eruptions from small to colossal, raising concerns on the theoretical possibility to predict the magnitude and impact of impending volcanic eruptions.
Photo 1 - Eruption of the Soufriere Hills Volcano, Montserrat Island, Antilles, 1997.
Volume of volcanic products greater than 10 million cubic meters.
Photo B. Voight.
Photo 2 - Piñatubo volcano eruption, Philippines, 1991.
Volume of volcanic products greater than 10 cubic kilometers.
US Geological Survey photo.
Image 3 - The study allows to determine the frequency on a global scale of eruptions of different sizes. Explosive eruptions are distributed according to a power law, represented by the rectilinear trend shown by the blue dotted line.