NAPLES, Italy -- Mount St. Helens, the rumbling volcano in Washington state, has belched out dramatic columns of steam and ash in the past week, but here in Naples, volcano experts regard all the excitement across the Atlantic as a mere diversion.
The area around Mount St. Helens is largely uninhabited. But Mount Vesuvius stands within the Naples megalopolis of 5 million inhabitants. Keeping tabs on it is a matter of massive life and death. No volcano on Earth could put as many people in immediate danger.
Mount Vesuvius last erupted on March 17, 1944, shortly after the arrival of Allied forces in Naples during World War II. Contingency plans in place would call for the evacuation of 600,000 residents from 18 towns sitting on the skirt of the ancient volcano.
"Our Vesuvius is the one to watch out for," said Giovanni Macedonio, director of the Vesuvius Observatory, a venerable institution dedicated to keeping tabs on the volcano's mood.
Because Vesuvius has not erupted since 1944, the responsibility for Macedonio and his 90 experts is ever more crucial. The longer a volcano sleeps, the more powerful an explosion is likely to be when it awakens, Vesuvius monitors say.
If the observatory decides that Vesuvius is about to erupt, a series of wide-reaching emergency measures would be set into motion. Chief among them would be the evacuation of 600,000 residents in 18 towns that sit on the volcano's skirt. "We are not working to let tourists know when to visit," Macedonio said.
In the mid-1990s, the Italian government designed a plan for evacuating the slopes of Vesuvius by transferring residents to preselected towns across Italy. But some of the orders attracted ridicule. Citizens of Torre del Greco, a city on the coast, were told to await trains and boats to take them to Sicily. At first, they were told to go either to Sicily or Sardinia, but complaints about being split between island provinces forced the government to choose one. Residents were also told to check in with the mayor's office before leaving, a request critics called an invitation to chaos.
Evacuation drills have not resolved residents' concerns: Typically, only a few hundred citizens have taken part, boarding buses and given wine and cake for trips to the Italian hinterland. Some mock evacuations were interrupted by herds of sheep crossing roads.
In any event, the evacuation plan assumes having at least a two-week notice of an eruption. But some scientists note that the catastrophic 1980 eruption of Mount St. Helens was preceded by only a few hours of turbulence. A disastrous eruption of Mount Vesuvius in 1631 was preceded by weeks of tremors and puffs of smoke, yet 4,000 people died when lava and water blew from the crest of the mountain.
Fear of crying wolf haunts Vesuvius Observatory scientists. "People are skeptical as it is," said Macedonio. If an evacuation is ordered and the mountain does nothing, "imagine the criticism," he said. "Imagine the economic costs of making a mistake. And when would we be able to tell everyone it's safe to return home?"
In the observatory, a nondescript, glass-faced building in Naples, Macedonio inspected rows of television screens that monitor the innards of the snoring volcano along with the minute heaving of its surface and the emissions of gases from its core.
It is tedious, repetitive work that goes on 24 hours a day, seven days a week. Even a minor tremor gets a long look. On one screen, the steady scribbling on a seismograph suddenly expanded into long up-and-down scratches. It was a mild earthquake to the north of Naples that lasted barely a second.
No cause for alarm, Macedonio said, "The ground is very much alive around here."
New technology has given researchers observation tools on land, below ground and in space. Seismic measuring devices are positioned around the mountain and two sensors have been lowered 200 yards into the mountain to record subterranean shifts. Lately, the observatory has been supplied with European Space Agency satellite feeds that offer real-time recordings of up or down movements of the earth of even a few millimeters.
"We are looking at Vesuvius in more ways from more angles than ever," said Marcello Martini, of the National Institute of Geophysics and Volcanology. "But we still don't know all the variables that exist inside Vesuvius. An exact time factor is not in our powers to predict."
Five years ago, the observatory tried to map the interior of Vesuvius by setting off explosions beneath the ground and at sea, measuring the echoes and using sonar. The results showed that a magma pool fills a space between five and seven miles deep spreading over an area 13 miles by 13 miles.
But for all the high-tech equipment, old methods still count. "If someone comes to us and says his well is dry, we would look into it very seriously," Macedonio said.
Mount Vesuvius is arguably the most recorded volcano in history. The eruption in 79 AD that buried Pompeii in a sea of mud and ash was described in detail by Pliny the Younger, the Roman senator whose uncle, an admiral, died in a seaborne rescue attempt. "Ashes were already falling, hotter and thicker, as the ships drew near, followed by bits of pumice and blackened stones, charred and cracked by the flames," Pliny wrote. "Meanwhile, on Mt. Vesuvius, broad sheets of fire and leaping flames blazed at several points, their bright glare emphasized by the darkness of night."
After that, the volcano erupted every century or so for a thousand years. It then went dormant until 1631. During the next four centuries, it blew its top 21 times.
In recent centuries, travelers included Naples on the grand tour of cultural centers in Italy, and some hiked to the crater. Painters recorded its spectacular explosions. In 1787, the German writer Johann Wolfgang von Goethe climbed into the crater after a minor eruption and got lost in smoke.
"I had only taken fifty steps when the smoke became so dense that I could hardly see my shoes," he wrote. "The handkerchief I pressed over my mouth was no help. In addition, my guide had disappeared and my steps on the little lava chunks, which the eruption had discharged, became more and more unsteady. I thought it better, therefore, to turn back and wait for a day with less cloud and less smoke."
The mountain became the object of intense scientific study in 1844, when Ferdinand II, the Bourbon monarch in Naples, ordered a palatial observatory built near the summit and stocked it with seismographs. These days, buses bring tourists to a restaurant from which they can climb to the top and gaze into the crater. The old observatory is now a museum.