Scholars claim that the volcano has been silent since 1944 (it had been a limited eruption in the middle of the American occupation) and that it is preparing for an explosive awakening in the centuries to come. Their convictions were developed by studying previous eruptions of Vesuvius. Volcanologists have collected a lot of data: volume of emissions identified the area where the gases deposited, analysed the ashes and studied the extent of the destruction. The studies and investigations are fundamental to understand the precise nature of the volcano's hydraulic system, thus giving researchers the tools to accurately predict the dynamics and risks associated with the next eruptions.
The results are not very reassuring for those who live and work around the volcano: an avalanche that should radiate for seven kilometres around it is likely to destroy in less than 15 minutes. The chances of raising the alarm in time and preventing the risk are, of course, linked to the research still underway. It was 24 August 79 AD. Twenty kilometres away Pliny the Elder witnessed the explosion: the burning cloud of gas, ash and pumice stone rolled down the sides of Vesuvius and destroyed Pompeii and its surroundings. Later he buries Herculaneum and his inhabitants. Catastrophic. Terrifying.
But the Vesuvius risk is not in that cloud of fire that in the 15 minutes following the next eruption will destroy within a radius of seven kilometres, no, the risk is for the million and more people living on its slopes and without historical memory. The explosion could have devastating effects not because of the unpredictable strength of the volcano, but because of the well-known weakness of prevention. The reason is written in the history of the last seventeen thousand years of Vesuvius and laboriously but effectively reconstructed by volcanologists. In the second half of March 1944, the volcano carried out its last, spectacular eruption and closed the cycle inaugurated in 79 A.D. and lasted about 2000. And he entered indefinitely into that phase which he defined as “dynamic rest”. While outside everything is silent, in the volcano has accumulated from 50 to 100 cubic kilometres of magma ready to be violently expelled outside in the “maximum expected event” that could be an eruption similar to the one that destroyed Torre del Greco in 1631 or a real Plinian eruption, like the famous one of Pompeii and Herculaneum, in any case, the next eruption of Vesuvius, that could happen in a few years or in a few centuries, will open the ninth cycle in the activity of the volcano documented in the last 17 thousand years.
The risk for the million people who, forgetting the past, have invaded the slopes of the volcano will be much earlier, when days and perhaps weeks in advance Vesuvius will launch the first, unmistakable signs of its next awakening. Then the rats and snakes will leave the mountain, the waters of the wells will become turbid (as in 1631) and the experts of the Vesuvius Observatory will detect the resumption of seismic activity and the variation in the composition of gases, magnetic, electric and even gravitational fields. To put into practice a serious evacuation plan for the Vesuvian area, it will be necessary to warn with great tact those millions of people with no historical memory and little risk education.