figure 1 3D view of Vesuvius and the inhabited centers on its slopes, seen from the West; DTM with superimposed color digital orthophoto (Laboratory of Geomatics and Cartography, INGV-OV).
Picture 1The inhabited area around Vesuvius volcano in a 3D perspective view from West; DTM overlaid with digital color orthophoto (Laboratory of Geomatics and Cartography, INGV-OV).
figure 2 Pyroclastic deposits within the town of Pompeii which include stratified levels with traction structures formed by Pyroclastic Currents
Picture 2 Pyroclastic deposits within the Pompeii inhabited area including stratified layer with tractional structures formed by the Pyroclastic Density Currents
Pompeii: determined the duration of the pyroclastic currents generated by the eruption of Vesuvius in 79 AD
A research on the effects of the pyroclastic flows of the 79 AD eruption on Pompeii has highlighted how their duration has had a tragic impact on the population
About fifteen minutes was the duration of the pyroclastic currents that hit Pompeii during the eruption of Vesuvius in 79 AD: their volcanic ashes, inhaled by the inhabitants, were fatal, causing asphyxiation.
This is what the study The impact of pyroclastic density currents duration on humans: the case of the AD 79 eruption of Vesuvius reveals, conducted by the University of Bari - Department of Earth and Geoenvironmental Sciences, in collaboration with the National Institute of Geophysics and Volcanology (INGV) and the British Geological Survey of Edinburgh, just published 'Scientific Reports'.
"The objective of the work", says Roberto Isaia, a researcher at the INGV Vesuvius Observatory, "was to develop a model to try to understand and quantify the impact of pyroclastic flows on the town of Pompeii".
In fact, pyroclastic flows are the most devastating phenomenon of the so-called explosive eruptions. Comparable to avalanches, they are generated by the collapse of the eruptive column. The resulting dense streams flow down the slopes of the volcano at speeds of hundreds of kilometers per hour, at high temperatures and with a high concentration of particles.
“For our research”, continues Isaia, “we carried out studies on the ground and in the laboratory of the pyroclastic deposits present within the archaeological excavations of Pompeii which led to the measurement and definition of the physical-mechanical parameters of the rocks. With the data obtained, we developed a mathematical model that allowed us to carry out numerical simulations. From these we obtained the physical parameters of the pyroclastic currents and, therefore, estimated their effects on the territory, including humans. The main result is that the persistence of the passage of the pyroclastic currents took place in a period of time between 10 and 20 minutes”.
“The elaborated model” adds the researcher, “can also be applied to other active volcanoes around the world. In fact, the example of Pompeii, about 10 km from Vesuvius, suggests that the application of this model could be very useful for understanding the duration of pyroclastic flows and, therefore, the damage deriving from an eruption even at distances where the temperature and the pressure of pyroclastic currents no longer causes harmful effects on humans and the environment. The methodology applied can therefore provide new elements of knowledge in the field of hazard assessments of an active volcanic structure”, concludes Roberto Isaia.
"It is very important to be able to reconstruct what happened in the past eruptions of Vesuvius starting from the geological record, to trace the characteristics of the pyroclastic currents and the impact on man" declares Prof. Pierfrancesco Dellino of the University of Bari, referent for the sector volcano of the National Major Risks Commission. "The approach we followed adds information that is contained in the pyroclastic deposits and that clarifies new aspects of the Pompeii eruption and provides valuable insights for interpreting the behavior of Vesuvius also in terms of civil protection".
The board
Who: University of Bari, National Institute of Geophysics and Volcanology (INGV) and British Geological Survey of Edinburgh (UK)
What: Developed a model which made it possible to calculate that in Pompeii the persistence of the passage of pyroclastic currents occurred in a period of time between 10 and 20 minutes causing lethal effects on its inhabitants
Where: The study The impact of pyroclastic density currents duration on humans: the case of the AD 79 eruption of Vesuvius in 'Scientific Reports'.
Link: https://www.nature.com/articles/s41598-021-84456-7
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PRESS RELEASE
Pompeii: the duration of pyroclastic currents generated by the eruption of Vesuvius in 79 AD has been determined
A research on the effects of the pyroclastic flows of the 79 AD eruption on Pompeii highlighted how their duration had a tragic impact on the population
About fifteen minutes was the duration of the pyroclastic currents that hit Pompeii during the eruption of Vesuvius in 79 AD: the volcanic ashes, inhaled by the inhabitants, were fatal, causing asphyxiation.
This is what reveals the study “The impact of pyroclastic density currents duration on humans: the case of the AD 79 eruption of Vesuvius”, conducted by the University of Bari - Department of Earth and Geo-environmental Sciences, in collaboration with the Istituto Nazionale of Geophysics and Volcanology (INGV) and the British Geological Survey of Edinburgh. The study has just been published 'Scientific Reports'.
"The aim of the work", says Roberto Isaia, senior researcher of the Vesuvian Observatory of the INGV "was to develop a model to try to understand and quantify the impact of pyroclastic flows on the inhabited area of Pompeii".
Pyroclastic flows, in fact, are the most devastating phenomenon of the so-called explosive eruptions. Comparable to avalanches, they are generated by the collapse of the eruptive column. The resulting dense pyroclastic flows flow along the slopes of the volcano at speeds of hundreds of kilometers per hour, at high temperatures and with a high particle concentration.
“During our research”, continues Isaiah, “we carried out filed and laboratory studies of the pyroclastic deposits recognized within the archaeological excavations of Pompeii which led to the measurement and definition of the physical-mechanical parameters of the rocks. The obtained data have been used as input parameters for a mathematical model that has allowed us to carry out numerical simulations. From these we obtained the physical parameters of the pyroclastic currents and, therefore, the effects on the territory, including people, have been estimated. The main result is that the persistence of the flow of pyroclastic currents took place over a period of time between 10 and 20 minutes".
“The developed model” adds the researcher, “can also be applied to other active volcanoes around the world,. The example of Pompeii in fact, about 10 km far from Vesuvius, suggests how the use of this model could be very valuable for understanding the duration of pyroclastic flows and, therefore, the damage deriving from an eruption even at distances where the temperature and the pressure of the pyroclastic currents no longer causes harmful effects on humans and the environment. The applied methodology can therefore provide new elements of knowledge in the context of the hazard assessment of an active volcanic structure", concludes Roberto Isaia.
"It is very important to be able to reconstruct what happened in the past eruptions of Vesuvius starting from the geological record, in order to trace the characteristics of the pyroclastic currents and the impact on population" declares Professor Pierfrancesco Dellino of the University of Bari, referent for the sector volcanic activity of the National Major Risks Commission. “The adopted scientific approach in this study reveals information that are contained by the pyroclastic deposits and that clarifies new aspects of the eruption of Pompeii and provides valuable insights for interpreting the behavior of Vesuvius also in terms of civil protection".
briefly
Who: University of Bari, National Institute of Geophysics and Volcanology (INGV) and British Geological Survey of Edinburgh (UK)
What: A model was developed that allowed to calculate that in Pompeii the persistence of the passage of pyroclastic currents occurred in a period of time between 10 and 20 minutes, causing lethal effects on its inhabitants.
Where: The research The impact of pyroclastic density currents duration on humans: the case of the AD 79 eruption of Vesuvius in 'Scientific Reports'.
Link: https://www.nature.com/articles/s41598-021-84456-7
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Extended
Pyroclastic density currents are ground hugging gas-particle flows that originate from the collapse of an eruption column or lava dome. They move away from the volcano at high speed, causing devastation. The impact is generally associated with flow dynamic pressure and temperature. Little emphasis has yet been given to flow duration, although it is emerging that the survival of people engulfed in a current strongly depends on the exposure time. The AD 79 event of Somma-Vesuvius is used here to demonstrate the impact of pyroclastic density currents on humans during an historical eruption. At Herculaneum, at the foot of the volcano, the temperature and strength of the flow were so high that survival was impossible. At Pompeii, in the distal area, we use a new model indicating that the current had low strength and low temperature, which is confirmed by the absence of signs of trauma on corpses. Under such conditions, survival should have been possible if the current lasted a few minutes or less. Instead, our calculations demonstrate a flow duration of 17 min, long enough to make lethal the breathing of ash suspended in the current. We conclude that in distal areas where the mechanical and thermal effects of a pyroclastic density currents are diminished, flow duration is the key for survival.