Sunday, April 18, 2010

Vesuvius- Asleep for Now. National Geographic


Asleep for Now

September 2007

National Geographic
By Stephen S. Hall

When the first thunderous boom echoed across the plain of Campania, quickly followed by a blistering hail of volcanic rock, the man and the woman hastily abandoned their village and made a run for it to the east, up a gently sloping hill toward what must have seemed like possible sanctuary in a nearby forest. She was about 20 years old; he was in his mid-40s. A violent downpour of rubbly pumice mixed with incandescent rocks capable of crushing skulls and scalding skin obscured their escape. To their uncomprehending minds, the calamity descending upon them must have seemed like the end of the world.

Thousands of other people were at that same moment running for their lives, marking the soft ash and wet volcanic mud with footprints of human desperation that would remain undiscovered for millennia. The people whose footprints led to the north or northwest chose a path that probably saved their lives; those who set out to the east, like the young woman and the older man, toward the present-day Italian town of Avellino, unwittingly chose a path that led to certain death. They headed, by ill luck, smack into the middle of a fallout zone that would be swiftly buried under three feet of pumice.

Battered by the fallout as if stoned by the gods, weary with the effort and terrorized by the darkness that descended around them, each breath more labored than the one before, the couple—surely united in their desperation if not by any ancient form of matrimony—began to slow down. After struggling part way up the hill, a hill that rises toward a promontory now called Castel Cicala, they finally collapsed and fell to the ground, in the final throes of asphyxiation.

"They couldn't have seen more than a few feet in front of themselves," Giuseppe Mastrolorenzo was saying. A volcanologist at the Osservatorio Vesuviano in Naples, Mastrolorenzo stood in a small, well-lit room in the Museum of Anthropology at the University of Naples, leaning over a display case containing the beautifully preserved skeleton of the young woman extended on a bed of pumice, just as it had been found.

"In the eruption that buried Pompeii and Herculaneum, the deaths were instantaneous. People didn't know what was happening to them," added Pier Paolo Petrone, the anthropologist who had excavated and analyzed the woman's skeleton. "But her death was more tragic because it wasn't sudden." In one final, futile gesture of self-protection, the woman and the man raised their arms to shield their faces—and wore that fretful salute into eternity.

The bones lay where the couple fell until December 1995, when Italian archaeologists, digging a test hole for a future gas pipeline outside the small town of San Paolo Bel Sito, about ten miles (16 kilometers) northeast of Vesuvius, discovered a human skeleton nested in the roots of a hazelnut tree. It was the woman. Soon after, they uncovered a second skeleton, the man, beside the first.

Organized crime has made a lamentable comeback in the squat, dusty towns surrounding Naples, and when workers stumble upon human remains, it's sometimes a tough decision whether to call in an archaeologist or a homicide detective. Not in this case. The skeletons' final resting place, a bumpy bed of volcanic rock covered by pumice, provided a precise geologic time stamp for the moment of death. All that was required was a volcanologist to read the layers of rock. That process was set in motion when Petrone and Mastrolorenzo got news of the discovery. Petrone rushed to the site; authorities granted him exactly two afternoons to extract the bones. "It was a miracle that we were able to save this," Petrone said.

The skeletons of San Paolo Bel Sito—frozen in terrified flight, their choice of a mistaken escape route immortalized in their weary, ossified repose—offered Italian scientists clues in a project that has combined volcanology, archaeology, and physical anthropology into something like a CSI: Vesuvius. Over the past decade the project has rewritten the story of the nearby volcano, adding ominous fuel to scientific debates about the danger of future eruptions.

The man and woman were not doomed refugees of the famous A.D. 79 eruption that buried Pompeii and Herculaneum. Rather they were Bronze Age inhabitants of one of the dozens of prehistoric villages that dotted this beautiful, fertile plain during an earlier—and, it turns out, more violent—eruption of Vesuvius. The Avellino eruption occurred approximately 3,780 years ago, and researchers now argue that it represents the nightmare blueprint for a future calamity that could envelop Naples itself.

Since 1995, Petrone and Mastrolorenzo have roved the countryside of Campania, the region that surrounds Naples, a bit like the archaeological version of storm chasers, hustling to newly discovered excavation sites before the evidence can be removed or covered up. They have pieced together an anthropological and volcanological picture of the Avellino eruption—from thousands of fleeing footsteps of its victims, preserved in volcanic ash, to a spectacularly preserved prehistoric village (since dismantled) that was practically abandoned with dinner on the table—that has redefined the volcanic might and environmental toll of Vesuvius. They have not only given eloquent voice to the skeletons of San Paolo Bel Sito, but their enterprising research has turned that voice into a stark warning: Beware, modern Naples and surroundings, with your three million inhabitants, because an eruption of this magnitude is likely to happen again, and perhaps (in geologic time) very soon.

Ancient peoples gravitated to the plain of Campania for the same reasons we do today: clement weather, access to the sea (and sea-food) at the present-day Gulf of Naples, fertile volcanic soil, and perhaps even the beauty that has captivated writers from Virgil to Stendhal. Long before Aeneas returned from his travels, more than a thousand years before Greeks settled in Cumae and ruled the Campanian plain, prehistoric settlers came down out of the nearby Apennines and began to tame the land, growing cereal crops and tending flocks.

Later the Greeks moved east from Cumae to Neapolis, the New City, a little farther along the coast where modern Naples now stands. We have a very good idea what life in this sun-splashed land was like during the Roman era because of the recovered splendor of Pompeii and Herculaneum. But as the well-trod earth of Campania continues to yield ancient secrets, Mastrolorenzo and Petrone, with their colleague Lucia Pappalardo, have put together a rich view of an earlier time and what may have been humankind's first encounter with the primal force of Vesuvius.

Almost all has come to light by chance. In May 2001, for example, construction workers began digging the foundation for a supermarket next to a desolate, weed-strewn intersection just outside the town of Nola. An archaeologist working for the province of Naples noticed several traces of burned wood a few feet below the surface, an indication of earlier human habitation. At 19 feet (6 meters) below, relicts of a perfectly preserved Early Bronze Age village began to emerge.

Over the next several months, the excavation unearthed three large prehistoric dwellings: horseshoe-shaped huts with clearly demarked entrances, living areas, and the equivalent of kitchens. Researchers found dozens of pots, pottery plates, and crude hourglass-shaped canisters that still contained fossilized traces of almonds, flour, grain, acorns, olive pits, even mushrooms. Simple partitions separated the rooms; one hut had what appeared to be a loft. The tracks of goats, sheep, cattle, and pigs, as well as their human masters, crisscrossed the yard outside. The skeletons of nine pregnant goats lay in an enclosed area that included an animal pen. If a skeleton can be said to cower, the bones of an apparently terrified dog huddled under the eaves of one roof. What preserved this prehistoric village, what formed a perfect impression of its quotidian contents right down to leaves in the thatch roofs and cereal grains in the kitchen containers, was the fallout and surge and mud from the Avellino eruption of Vesuvius. Claude Albore Livadie, a French archaeologist who published the initial report on the Nola discovery, dubbed it "a first Pompeii."

During May and June 2001, provincial archaeological authorities oversaw excavation of the site. Mastrolorenzo hurried out to Nola, about 18 miles (29 kilometers) east of Naples. He and Pappalardo took samples of the ash and volcanic deposits, which contained chemical clues to the magnitude of the eruption. But then the scientific story veered off into the familiar opera buffa of Italian archaeology. The owner of the site agitated for construction of the supermarket to resume or to be compensated for the delay—not an unusual dilemma in a country where the backhoes and bulldozers of a modern economy clang against the ubiquitous remains of ancient civilizations.

Government archaeologists hastily excavated the site and removed the objects. As it turns out, the supermarket was never built, and all that remains of a site that miraculously captured one of civilization's earliest encounters with volcanic destruction is a hole in the ground on a vacant, weed-choked lot, the foundation walls of the huts barely visible. A small, weathered sign proclaiming the "Pompeii of Prehistory" hangs limply from a padlocked gate.

The sad archaeological scenario of Nola has repeated itself several times. In 2002, an Italian construction company under contract to the U.S. government to build a support facility for the large U.S. Navy base in the southern Mediterranean uncovered another ash-covered village near the modern town of Gricignano di Aversa; it was, according to Mastrolorenzo, even more extensive than the Nola site, with traces of numerous Copper and Bronze Age huts. "They spend a short time 'documenting' the site," Petrone said sarcastically of archaeologists who examine construction sites, "and then it is destroyed."

In the summer of 2004, during construction of the new high-speed railroad line between Naples and Rome, thousands of human footprints were uncovered near the town of Afragola. Geologic analysis established that they were the footprints of Bronze Age inhabitants fleeing the Avellino event. The threesome rushed to photograph the vivid residue of that ancient terror.

Despite the loss of these sites, Mastrolorenzo, Petrone, Pappalardo, and American volcanologist Michael Sheridan triggered worldwide fascination when they summarized these findings in the spring of 2006 in the Proceedings of the National Academy of Sciences (PNAS). But their research went beyond mere archaeological documentation. The Avellino event, they wrote, "caused a social-demographic collapse and the abandonment of the entire area for centuries." The new findings, along with computer models, show that an Avellino-size eruption would unleash a concentric wave of destruction that could devastate Naples and much of its surroundings. In the world before Hurricane Katrina and the Indian Ocean tsunami, these warnings might have sounded as remote and transitory as those prehistoric footsteps. Not anymore.

There are many ways for a human being to die after a volcano erupts, and a blast like the one Vesuvius unleashed in 1780 B.C. provides a grim inventory of almost all of them. "In the first hours of the Avellino eruption, material like this fell," Mastrolorenzo explained, dropping two transparent bags of volcanic material on the desk in his office at the Osservatorio Vesuviano. One of the bags contained a fine white powder, the ash that blanketed the fallout zone; the other was full of small rocks, no more than an inch or two in diameter. Some of the rocks were pumice, pebbles honeycombed with bubbles and nearly as light as Ping-Pong balls; others were dense and hard. "These are lighter than water; they float," he said, picking up a piece of pumice. "But these," he continued, picking up one of the harder rocks, called lapilli, "these were falling at about 90 miles (145 kilometers) per hour."

The first hint of the Avellino eruption of Vesuvius emerged in the early 1970s when volcanologists identified pumice deposits underneath the A.D. 79 residues. But in recent years Mastrolorenzo, Pappalardo, and their colleagues, analyzing everything from meters-thick ash deposits visible in road cuts to micron-thin slices of volcanic crystals viewed in a scanning electron microscope, have reconstructed the Avellino event in harrowing detail.

Some eruptions ooze lava in picturesque, slow-moving streams. But in an event like Avellino, the conduit of the volcano is so tightly corked by solid rock that it takes an enormous amount of pressure building up from below, in the magma chamber, to blow a hole to the surface. When it does, the violence of the explosion—the boato, Italian for the enormous roar—propels liquid rock into the air so fast that it breaks the sound barrier, unleashing a sonic boom. During the Avellino eruption, the boato accompanied a blast that hurled nearly 100,000 tons a second of superheated rock, cinders, and ash into the stratosphere. It reached an altitude of about 22 miles (35 kilometers)—roughly three times the cruising altitude of commercial airliners. As this incredible cloud of material rose, it spread at the top, assuming the classic shape—classic ever since Pliny the Younger first described it in a letter to the Roman historian Tacitus about the later eruption that buried Pompeii—of an umbrella pine tree, the iconic feature of a plinian eruption.

Prevailing winds out of the west carried the bulk of the initial fallout in a northeasterly direction, toward Nola and Avellino, where pumice and lapilli deposits piled up as high as nine feet (three meters) near the volcano in several hours. The column of ash may have hovered in the air for up to 12 hours. Then it collapsed, producing an apocalyptic sequence of events that makes a plinian eruption one of the most lethal natural disasters on Earth.

When a plinian column falls upon itself, it creates a pyroclastic surge—a boiling, turbulent avalanche of debris that shoots out sideways from the slopes of a volcano. This searing cloud can travel for many miles, initially at great speed. Not too many humans have seen (much less survived) a pyroclastic surge at close quarters, but many of us have an image of its horrifying power burned into our memories: It shares many physical properties with the huge clouds of powder and ash produced by the collapse of the World Trade Center towers in 2001.

Unlike the collapsed towers, the material in a pyroclastic surge is baked in a subterranean magma chamber to temperatures of up to 1650°F (899°C). The initial surge of the Avellino eruption, especially in the zones closest to Vesuvius, was instantly lethal. Hot, choking wind, advancing at about 240 miles (386 kilometers) an hour, reached temperatures of at least 900°F (482°C), and retained enough heat to bring water to a boil ten miles (16 kilometers) from the vent. "Below 200 degrees Fahrenheit (93°C), you can survive for several seconds, perhaps, if the wave passes quickly," Mastrolorenzo pointed out. "But even if you survive the temperature, you will suffocate on the fine powder in the air. The entire countryside surrounding Vesuvius was covered by foot upon foot of this powder, 65 feet (20 meters) deep at a distance of three miles (five kilometers) from the crater to about ten inches (25 centimeters) thick at a distance of 15 miles (24 kilometers). Eight inches (20 centimeters) of ash is enough to cause modern roofs to collapse."

The sizzling temperature of a Vesuvian surge has emerged as a key factor in explaining what happened at Pompeii and Herculaneum in the next great eruption, 1,900 years later. Petrone and Mastrolorenzo, with colleagues in Italy and England, published a paper in the journal Nature in 2001 demonstrating that hundreds of fugitives who gathered in 12 seafront fornici, or boathouses, facing the beach of Herculaneum died instantly from a pyroclastic surge that reached temperatures of 932°F (500°C), vaporizing clothing and flesh within seconds.

In a grim bit of forensic paleoanthropology, Petrone and Mastrolorenzo reconstructed a parting picture of the victims huddled inside fornici 5, 10, and 12. The heat would have boiled their brain tissue, which would then have burst out in small, scalding explosions that left blue-black burn marks on the bone. Moisture from vaporized flesh and blood combined with volcanic ash in the surge to create a protective, plasterlike material that preserved the bones, and from the posture of the skeletons they could determine that victims in the fornici died instantly. (Petrone keeps samples of the bones, along with the San Paolo Bel Sito skeletons, in several large shopping bags in his office.)

The pyroclastic surge is just the first part of the one-two punch delivered by the collapse of a plinian column. When the vast amount of solid ash and debris mixes with steam fed by underground aquifers, a violent microclimate of pitched thunderstorms and torrential rains occurs, producing great mudflows. Ash falling into rivers creates more mudflows, known as lahars, that fill river valleys long after the eruption is over. "There are more victims from the mudflows than from the eruption itself," Mastrolorenzo says. "These mudflows travel with a force that moves houses hundreds of meters."

Blast, fallout, column collapse, surge, flow: In this classic sequence of plinian fury, the Avellino eruption disfigured the plain of Campania as rudely as if the gods had scraped, gouged, and reshaped the landscape with a giant trowel. The pattern of its deposits, the swirl of its volcanic signature in layers thick and thin, has allowed volcanologists to conclude that Vesuvius unleashed at least six cycles of pyroclastic surge and flow in that single eruption—six bursts of searing winds followed by six rampaging rivers of mud—that destroyed everything within about nine miles (14 kilometers) of the volcano. The immediate cataclysm probably lasted less than 24 hours, but it turned an idyllic landscape into a monochromatic desert, uninhabitable for 300 years.

The road that snakes up from the Gulf of Naples to the summit of Vesuvius reveals one more way a human being can perish on the slopes of this volcano: getting hit by one of the countless tour buses careening around the tight turns along the route from Ercolano to the 4,203-foot (1,281 meters) summit. Long gone are the days when brawny Neapolitan youths hoisted chairs bearing celebrities like Goethe and lugged them up the steep path to what the German writer memorably called "this peak of hell which towers up in the middle of paradise." Paradise nowadays is finding a free spot in the crowded car park.

After buying your ticket (the top of the volcano is now part of a national park), you hike along a path zigzagging over the rusty, iron-rich cinders of the cone. You pass several souvenir shops as well as the abandoned concrete piers of the funicular cableway that replaced the broad-shouldered youths (the original 19th-century version of this conveyance inspired the famous Neapolitan song "Funiculì, Funiculà"). And finally, you arrive at the rim of the crater, where the view on a clear day takes in everything from Capri and the Sorrentine Peninsula to the south, to modern-day Naples to the northwest, to Pompeii and Herculaneum, victims of the geophysical power momentarily contained beneath your feet.

After an enormous sub-plinian eruption in 1631, Vesuvius has adopted a more benign personality. It produced copious streams of lava during frequent eruptions in the 18th, 19th, and early 20th centuries (when Mastrolorenzo was a child, his grandmother used to describe the time his grandfather swept ash and cinders off roofs in Naples following an event in 1906). But since its last eruption in 1944, the conduit has been plugged, and no one younger than 63 years of age has experienced an eruption. The occasional reminders that the volcano is still active produce a complex state of philosophical denial among people who live on or near Vesuvius. They tend to pooh-pooh the danger and, perhaps more than in many other parts of Italy, live for the moment in a gracefully fatalistic way.

Few people spend more waking hours, day in and day out, in close proximity to Vesuvius than Gennaro Cardoncello, a stolid and friendly young man who tends the last outpost of commerce on the crater rim. As he stood behind a truly astonishing array of curios carved from volcanic rock (Buddha, the Pietà, frogs, owls, the Three Graces), he was asked if he ever feels the small earthquakes or tremors that are believed to signal the run-up to an eruption.

"Maybe a few times, but it's not a big deal," he said. With that sloe-eyed look of indifference that has been elevated to performance art in Naples and environs, Cardoncello shrugged his shoulders and changed the subject, producing a bottle of Lacryma Cristi, the local white wine whose grapes draw on Vesuvius's rich soil to produce their intense taste.

Streams of tourists clamber up the steep path to the crater, oohing at the postcard-perfect vistas in every direction, aahing as they peer down from the rim of the crater 800 feet (244 meters) to the floor, where several fumaroles barely manage to etch the air with their noxious breath. Few of these volca-tourists pause to think about the vast reservoir of molten rock about six miles (ten kilometers) below or contemplate the curving remnant of the larger, more ancient Monte Somma crater that funnels the view—and more important, would funnel any future pyroclastic surges—in a northwesterly direction toward metropolitan Naples. When Vesuvius had its last plinian eruption, the plain below was inhabited by thousands of sybaritic Romans; now it is inhabited by upwards of one million people in Naples alone, and hundreds of thousands more in the towns between the city and the crater.

On a clear day, with even modest binoculars, it is possible to stand on the crater rim and make out the massive 13th-century Angevin fortress in downtown Naples known as Maschio Angioino. Also known as Castel Nuovo, it is where the French Angevin monarchy first settled, and it marks the geographic and, in some ways, the emotional heart of the city. Several days after I visited the summit, Mastrolorenzo led me deep into the fortress's foundation, two floors beneath the elegant chamber where until recently the Naples City Council held its weekly meetings. He pointed to a deposit of volcanic pumice and ash roughly two and a half feet thick. It came, he said, from the Avellino eruption.

Michael Sheridan, a volcanologist at New York's University at Buffalo who collaborates with Mastrolorenzo, is an expert on catastrophic eruptions near densely populated urban centers. Sheridan has studied the 1902 eruption of Mount Pelée on the island of Martinique, which devastated the town of St. Pierre, and has been closely watching Cotopaxi, an active volcano that threatens more than a million people in the Andes highlands of Ecuador. He was unaware of the Castel Nuovo deposit until I mentioned it to him. "That's really damning," he said. "St. Pierre was destroyed by eight inches of that stuff, and everyone died. There would be no survivors in that part of Naples."

Scientists know from geologic records that Vesuvius has unleashed catastrophic plinian eruptions with a ragged but disquieting rhythm over recent geologic time. Since an eruption 25,000 years ago, major eruptions have occurred 22,500 years ago, 17,000 years ago, 15,000 years ago, 11,400 years ago, 8,000 years ago, then Avellino 3,780 years ago, and then the A.D. 79 Pompeii eruption nearly 2,000 years ago. Based on an interval of about 2,000 years between these larger eruptions, Sheridan and Mastrolorenzo have calculated that there is a greater than 50 percent chance of a major eruption each year now, the odds rising incrementally as the time since the last big plinian event grows longer year by year.

When Mastrolorenzo, Petrone, Pappalardo, and Sheridan published their research report on the Avellino eruption in March 2006, it sparked controversy with its blunt prediction that Vesuvius was due for a major eruption that could be powerful enough to threaten metropolitan Naples. Naples isn't even part of the current planning. The Italian emergency plan, introduced in 1995 and last revised in 2001, is based on a smaller, sub-plinian eruption and calls for the priority evacuation of the residents living in the immediate vicinity of Vesuvius—the 600,000 people who live in the so-called Zona Rossa, or Red Zone, defined by the boundaries of 18 municipalities on the slopes of the volcano.

The Vesuvius emergency plan has not been significantly updated in more than five years. When the PNAS paper came out last year, laying out a much more dire scenario for Naples, the president of Italy's National Institute of Geophysics and Volcanology, Enzo Boschi, denounced Sheridan's risk analysis as "alarmist and irresponsible," and flatly declared "the evacuation plans will not be changed." Some volcanologists at the University of Naples referred to the report's warnings as "scientific terrorism."

Predicting an impending eruption is an imprecise science at best. Although Mount St. Helens gave signs of increasing restlessness preceding the 1980 eruption, according to a U.S. Geological Survey account, it "showed no change from the pattern of the preceding month," and monitors on the morning of May 18, 1980, "revealed no unusual changes that could be taken as warning signs for the catastrophe that would strike about an hour and a half later."

If Vesuvius showed signs of rousing itself again, volcanologists believe they could predict that it was about to erupt in breve tempo, soon. When I asked Mastrolorenzo what exactly "soon" means, he replied: "This is the problem. We don't know—not in the way you can predict when a hurricane is likely to arrive." That imprecision could wreak havoc in a major metropolitan evacuation.

It's not nice to needlessly scare people, but it's much less nice to contemplate what happens when lots of scared people try to do the same thing in a big hurry at the same time. This thought occurred to me one afternoon as I sat, motionless, in a huge traffic jam on the Tangenziale, the expressway that threads around downtown Naples and leads to the main autostrada that heads north toward Rome.

What would happen if Vesuvius suddenly gave signs of becoming seriously restless? There would be, as there always is with probabilistic predictions, confusion and uncertainty. "It's hard to imagine what it would be like in the days leading up to an eruption," Mastrolorenzo said. "It would be worse than the eruption itself." Some Neapolitans might flee at the first hints of seismic indigestion, others might resolve to stay, still others might leave, grow disenchanted with weeks or months of seismic uncertainty, and then return. There simply is no modern precedent for an urban evacuation of this magnitude.

On the Tangenziale, cars inched along at a crawl; four lanes of cars jockeyed to squeeze into two northbound lanes. It took me about an hour to traverse a mile, and the most urgent thing on anyone's agenda that day was getting to the beach. Traffic like this makes any emergency evacuation plan seem hopelessly optimistic. Indeed, during a Red Zone evacuation drill in October 2006, traffic on the nearby Napoli-Pompeii autostrada ground to a halt; an overnight thunderstorm seriously complicated the exodus; and one of the 18 towns, Portici, participated under protest. Government officials pronounced themselves pleased with the results; news accounts described "delays and chaos." And this was just a minimalist exercise, involving only a hundred citizens from each of the 18 Red Zone towns.

In any event, a massive evacuation would have to be well under way prior to an Avellino-size eruption. Once the event began, once the volcano disgorged possibly billions of cubic feet of ash, rock, and debris into the air and sent it raining to the ground, all forms of transportation would become useless. Airplanes could not fly. Trains could not run. Neither cars nor buses nor scooters could function in even four or five inches of gritty ash. In fact, the only likely means of escape would be . . . by foot.

Four thousand years after Avellino, the inhabitants of Campania would be reduced to leaving their footprints in the ash.

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