Some of the rocks were pumice, pebbles honeycombed with bubbles and nearly as light as Ping-Pong balls; others were dense and hard. The first hint of the Avellino eruption of Vesuvius emerged in the early s when volcanologists identified pumice deposits underneath the A. 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 , 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 The initial surge of the Avellino eruption, especially in the zones closest to Vesuvius, was instantly lethal.
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, years later. In a grim bit of forensic paleoanthropology, Petrone and Mastrolorenzo reconstructed a parting picture of the victims huddled inside fornici 5, 10, and 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.
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 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,foot 1, 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.
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. 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 , 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 But since its last eruption in , 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.
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 feet 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. Share Tweet Email. Read This Next Wild parakeets have taken a liking to London. Animals Wild Cities Wild parakeets have taken a liking to London Love them or hate them, there's no denying their growing numbers have added an explosion of color to the city's streets.
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Most earthquakes and volcanoes occur as result of these plate boundaries. Volcano Photography. Vesuvius Observatory, is quoted as saying, "A marvelous thing, my Vesuvius. It covers land with precious ash that makes the earth fertile and grapes grow, and wine.
That's why, after every eruption, people rebuild their homes on the slopes of the volcano. That is why they call the slopes of Vesuvius the compania felix — the happy land. During the eruption, soldiers and airmen of the th Bomber Group were stationed at the Pompeii Airfield just a few miles from the base of the volcano.
Diaries record the awesome sights and sounds they witnessed in this latest major eruption. Guards wore leather jackets and "steel pot" helmets to protect themselves from rains of hot ash and small rocks.
Tents collapsed or caught fire when hot cinders were blown over them. Robert F. McRae wrote in his diary on March 20, , according to the American Geosciences Institute , "As I sit in my tent … I can hear at four- to second intervals the loud rumbling of the volcano on the third day of its present eruption.
The noise is like that of bowling balls slapping into the pins on a giant bowling alley. To look above the mountain tonight, one would think that the world was on fire.
The thickly clouded sky glows like that above a huge forest fire. Glowing brighter as new spouts of flame and lava are spewn from the crater. As the clouds pass from across the top of the mountain, the flame and lava can be seen shooting high into the sky to spill over the sides and run in red streams down the slopes. Today it is estimated that a path of molten lava 1 mile long, half a mile wide, and 8 feet deep is rolling down the mountain.
Towns on the slopes are preparing to evacuate.
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