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Chapter 3 Moving Ground Vesuvius and the Nola Mudslides of the Nineteenth Century Walter Palmieri Epilogue: Sarno, May 1998 In the wee hours between 5 and 6 May 1998, following two days of abundant rainfall, hundreds of thousands of cubic meters of mud and debris let loose on Mount Pizzo d’Alvano in the outskirts of Naples, sweeping down over the towns of Sarno, Quindici, Siano, and Bracigliano. The final toll listed 160 victims, hundreds of destroyed homes, whole areas completely devastated, and many millions of euros in damages. In subsequent weeks and months, the most common opinion of this terrible disaster was that it had been easily foreseeable. For years, scholars, geologists, and environmentalists had been raising the alarm about Italy’s hydrogeological risks, especially in Campania.1 Now, thanks to the general public uprising in the aftermath of the catastrophe, these experts finally had the opportunity to reach a wide audience and discuss the probable causes for what had happened: first and foremost, they blamed the geological fragility of that area, which is largely covered with unstable volcanic deposits from the eruptions of Vesuvius; next, they pointed out the steepness Vesuvius and the Nola Mudslides of the Nineteenth Century |  of slopes and the heavy rainfall. But according to these experts, alongside these “natural” factors were other causes that had contributed, directly or indirectly, to making that event particularly disastrous: the presence of settlements in high-risk areas at the mountain base, unauthorized building and waste disposal, little or no land maintenance, poor management of forest resources, lack of high-altitude meteorologic stations, and lack of forecasting and prevention plans.All these factors, of course, are anthropic. They involve human beings and their interaction with natural resources. One side effect of this tragedy’s high public visibility was an unusually wide interest in what Italian experts call franosità storica (landslide proneness ). Following the Sarno disaster, scholars began to investigate the area’s landslides and general hydrogeological instability over previous decades and centuries. Interestingly, this theme attracted the interest not just of geologists but also of several historians. As a result, in recent years numerous historical essays have appeared providing a detailed overview of what has happened in these towns from the seventeenth century onward.2 Until the appearance of these latest essays, however, Italian historians (and social scientists generally) rarely turned their attention to landslides, floods, or other hydrogeological disasters.Yet historical data has long been an important part of geological investigation. The presence of a rich record of landslides and floods provides an important means for predicting and preparing for future catastrophes of mud,water,and rock.One may hope that this new historical interest in landslide history will not prove ephemeral. Not only will this interest offer excellent opportunities for contributing to environmental history , it may also contribute to practical applications in the present. Slides under theVolcano Let us look deeper at the 1998 disaster. As mentioned previously, much of the area’s instability has been traced to the volcanic material that Vesuvius— continental Europe’s largest active volcano—spewed over gentle and rugged terrain east and northeast of Naples. Ash, pumice, and stones emitted by Vesuvius in its many eruptions over thousands of years was sedimented into the plains and slopes of the Campanian Apennines, forming deposits that sometimes reached thicknesses of several tens of meters, depending on distance from the crater, winds, and other factors. Yet these deposits have represented something of a paradox: since before ancient times, volcanic materials made Campania’s plains very fertile and favorable to human settlement, yet thick layers of these same materials on hills and slopes posed a major threat to inhabitants.  | Walter Palmieri This threat stems from the high permeability of pyroclastic covers. Rainwater readily trickles down through these layers to the underlying rock, which is much less permeable. As a result, the sinking water encounters an underground barrier so that during heavy rainfall, the superficial layer becomes soaked with water and is then lubricated on its underside to allow the whole mass to begin sliding and crumbling downhill. The resulting rapid mud-debris flows are among the most dangerous of landslides because they can carry huge quantities of material suddenly and violently, like an avalanche of rock. The high speed attained by these mudflows and the high kinetic energy they release require especially careful monitoring of areas where they are prone to occur. Disasters can only be avoided by preparing evacuation plans, as well as by preventing...

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