For two and a half months, the popular hot-springs resort of Banos in central Ecuador was a ghost town.
Twenty-five thousand residents of the town and nearby countryside had fled, or were evacuated on Oct. 16 after the nearby Tungurahua volcano came to life. Scientists warned there was an 80 percent chance of an eruption, and that hot gas and ash from Tungurahua -- "Throat of Fire" in the Quechua Indian language -- could overrun parts of Banos.
Since then the town has been spared by the tremors, steam explosions and ash clouds that have burst from the shuddering mountain. And now thousands of impatient "Banenos" are going home.
On Wednesday, 500 evacuees left their shelters laden with suitcases and household appliances, assembled in a caravan of trucks and buses, and headed for Banos.
Along the road, their numbers grew to 3,000. They clashed repeatedly with the few hundred police and army troops who tried to stop them with tear gas and clubs. One 22-year-old man was shot fatally in the chest, according to local press reports. Six people were injured and evacuees took nine servicemen hostage before the government gave in and agreed to let everybody go home.
It's precisely the scenario geologist C. Dan Miller feared. He is director of the United States' Volcano Disaster Assistance Program, which has been lending technical assistance to the country.
Tungurahua still fumes, but "nothing terrible has happened, so they're beginning to lose respect for the scientists and public officials. It always happens," says Miller.
He's seen it before. Since 1986, the volcano program has rushed experts and equipment to assist during eruptions in Montserrat, Indonesia, Papua New Guinea and throughout the Americas.
The residents of Banos really are in danger, he says. Eruptions in 1886, 1916 and 1918 sent torrents of hot ash, gas and mud down the same slopes that were evacuated in October. And some places have seen heavy ash falls.
Even so, scientists can't say for sure what will happen in Banos, or how long residents should stay away. The threat is likely to persist for years, Miller says.
The Banenos would not wait. After troops and police units pulled out of the city last Friday and stopped protecting property, the residents began trickling back, according to news reports. They reopened their shops, restaurants and the hot springs -- an international tourist attraction.
Men, women and children armed with sticks, machetes and rocks set up barricades in key streets to prevent the army from returning to force them out again.
Their leaders demanded a full troop withdrawal from the region, the free return of all residents, and "respect for human rights."
Tungurahua, and Guagua Pichincha -- another Ecuadorean volcano 80 miles north of Banos and just seven miles west of the capital city of Quito -- are two of the most dangerous volcanoes now active anywhere in the world, according to the U.S. Geological Survey. Its experts have been working with Ecuadorean geophysicists and government officials since 1998, when the two mountains began their current eruptions.
Pichincha and Tungurahua are both 16,000-foot "stratovolcanos." Like Mount Saint Helens and Mount Rainier in Washington state, and many others along the western mountain chains of the Americas, they have been built by thousands of years of eruptions.
Beneath them, huge chunks of the Earth's crust are clashing. The Nazca Plate beneath the eastern Pacific Ocean is being forced under the southern American Plate. As it descends, the Nazca Plate heats up and melts. The molten rock, or magma, then rises toward the surface. Shoving aside the overlying rock as it moves, it triggers a series of earthquakes.
When it reaches the surface, the liquid magma releases its load of dissolved gases like champagne when the cork is popped. The explosive eruptions release 1,200-degree gas, steam, incandescent ash and rock that can soar miles into the air. They then rain down on the countryside.
Sometimes the towering columns of hot ash collapse and fall in a hot "pyroclastic flow" -- what Miller describes as "a high-speed ash hurricane." Heavy rain can turn the fallen ash into raging mudflows, called "lahars."
Pyroclastic flows are "the kind of thing where people must be evacuated before they occur," Miller says. "They're too fast to outrun once they start."
Geologists have studied ash and mud deposits around Guagua Pichincha, and carbon-dated them using bits of charred wood found buried in them. They found the mountain has produced explosive eruptions roughly every 600 years for the last 12,000 years, the most recent in 970 A.D. and in 1660, after the Spanish conquest.
Quito's 1.8 million residents are relatively safe, however, thanks to mountains that stand between them and Pichincha's crater.