This geochemical study has used multiple research methods, such as bulk rock analyses and X-ray diffraction, to explore the causes for Vesuvius eruptions, their possible precursor phenomena and the expected effects of volcanic activity.
A Blog Article by Pablo Markin.
In March 2017, Francesco Stoppa, Claudia Principe, Mariangela Schiazza, Yu Liu, Paola Giosa and Sergio Crocetti have published a scholarly article bearing the title ‘Magma evolution inside the 1631 Vesuvius magma chamber and eruption triggering’ in Open Geosciences, an Open Access, peer-reviewed journal initially launched by Versita and Springer Science+Business Media as the Central European Journal of Geosciences in 2009. After the journal has been transferred to De Gruyter Open (formerly Versita), an imprint of De Gruyter, in 2014, the journal has been re-launched under its current title in Open Access format in 2015.
The key contribution of this paper to scholarly literature is a simplified description of the processes that take place between different Vesuvius eruptions, which has both historical and predictive aspects. More specifically, this article explores geological and structural reasons for the up-swelling of new magma batches from the deep geological layers of this mount and for the emplacement of a new magma chamber under Vesuvius. Moreover, this paper has proposed a parsimonious and precise manner to describe the evolution of magma inside this chamber and the possible factors leading to its eruption. By dint of this, the present research goes against the tide of the foregoing scholarship, since it sidesteps a widely accepted explanatory model for volcanic processes. This contributes to the scientific progress, as the proposed model of volcanic eruptions is significantly simpler than existing ones.
Given that no magma chamber under Vesuvius currently exists, it is important to investigate the reasons for the emplacement of a magma chamber under the volcano prior to the 1631 eruption. Likewise, this study has concentrated on the evolution of this chamber toward eruptive conditions eventually leading to the eruption of 16 December 1631, which was the last Plinian eruption at Vesuvius. The scientific community considers the Plinian model of eruptions to be the most probable eruptive scenario for the case in which Vesuvius can once again become an epicenter of volcanic processes leading to an explosive eruption. Therefore, the reconstruction of historical geological processes, such as the emplacement, evolution, and breaking of the 1631 magma chamber, that the authors of this article have performed is highly important for the forecasting of Vesuvius’s possible volcanic activity scenarios in the future.
Based on previous reconstructions of the eruptive phenomenology of the 1631 eruption, performed on the basis of field work and historical record analyses, the authors of this study have collected a statistically representative sample of eruptive products of this historical eruption. This study has used the classic petrochemical method involving an analysis of rock and mineral samples, to reconstruct the petrochemical evolution of the 1631 magma chamber. This research indicates that laboratory simulations, upon which existing scientific literature is based, cannot describe these natural processes with sufficient precision. Through its analytical conclusions based on primary data and comparisons with other Vesuvius deposits, the authors of this study have reconstructed the entire path of chemical evolution that has happened in the course of this magma up-swelling. Moreover, this research has identified several stages of magma rise, the nature of the parental magma of Vesuvius and the evolution this primitive magma inside the magma chamber up to the 1631 eruption event.
Therefore, this research sheds light on the manner in which volcanic activity at Vesuvius has taken place. It has found that this activity involves periodic up-swelling of primitive magma batches from the earth’s mantle and its progressive chemical evolution, first inside a deep reservoir and afterwards in a subterranean magma chamber. Inside this chamber, the magma evolved in a delicate equilibrium that was disrupted by repeated in-flows of fresh magma from a reservoir in the deep geological layers, which has led to the explosive eruption in 1631 AD. As this paper argues, this entire process has been controlled by crystal fractionation and settling mechanisms. These geological processes can also form the foundation for the future behavior of the volcano, while leading to the next explosive eruption. The explanatory model presented in this paper also indicates that fresh and relatively basic magma can reach directly the surface of the mount in the form of a lava flow, instead of leading to an explosive eruption. As this study, thus, suggests the up-swelling of magma, coming from a deep geological reservoir does not necessarily lead to explosive volcanic activity.
As this study of the 1631 eruption demonstrates, the re-emplacement of a magma chamber under Vesuvius cannot happen without magma arrival, chamber emplacement and its final destabilization, as has happened in the case of this eruption. This is the more probable scenario for the case of an explosive reactivation of Vesuvius. At the same time, as follows from this research, it is also possible that the volcano reactivation can happen by means of a relatively rapid eruption of a basic lava flow with a minor presence of long-term precursor factors and limited devastation as a consequence.
By Pablo Markin
Featured Image Credits: Mount Vesuvius, Italy, June 22, 2008 | © Courtesy of Katie Schenk.