We are concerned about Mt Helena, and it is in a largely uninhabited area. Mount Vesuvius, which has not had an eruption since 1944, has within it's sphere, FIVE Million Italians, almost 10% of Italy's entire population.

No volcano on Earth could put as many people in immediate danger.

The evacuation plan assumes having at least a two-week notice of an eruption. But  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 smoke, yet 4,000 people died when lava and water blew from the crest of the mountain.

NAPLES, ITALY--Mount St. Helens, the rumbling volcano in Washington state, has belched out dramatic columns of steam and ash in recent weeks, but 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 life and death on a large scale. No volcano on Earth could put as many people in immediate danger.

"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 of Macedonio and his 90 experts is ever greater. 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.

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.

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 smoke, yet 4,000 people died when lava and water blew from the crest of the mountain.

Fear of crying wolf haunts 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.

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 5 to 7 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 A.D. that buried Pompeii in a sea of mud and ash was described by Pliny the Younger. "Ashes were already falling, hotter and thicker ... followed by bits of pumice and blackened stones, charred and cracked by the flames," Pliny wrote. "Meanwhile, on Mount 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. 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.

In Italy, Vesuvius' clock is ticking
http://www.startribune.com/stories/484/5035230.html