"The avalanche alone probably would not have killed anyone," said Michael F. Sheridan, professor and chair of the Department of Geology at UB and leader of the team, "but Hurricane Mitch dumped about 2 feet of rain on Oct. 30, more than has ever been recorded in this area."

He said that the avalanche, caused by some very distinctive geologic features on the Casita volcano, together with the torrential rains, made for a lethal combination.

Last month, Sheridan presented research at the Geological Society of America's annual meeting that described how computers are being used to interpret satellite data to predict the likely sources, sizes and paths of volcanic debris flows so that populations at risk can be informed and evacuated. "What happened at Casita volcano is the perfect test case for my hypothesis, namely that satellite data can be used in conjunction with field work to provide a kind of 'geologic X-ray' to identify soft spots on the surface of volcanoes, particularly those that are vulnerable to collapse," he said.

Sheridan said the weakness on Casita originated deep inside the volcano with a geothermal circulation system that causes certain acid solutions to circulate through the rocks inside the volcano. "This causes the rock to be bathed in what is essentially an acid bath," he said, "so the minerals in the rock change to clays with hematite, or rust, coating the fractures. Over thousands of years, these acids cause the rock to become brittle and fracture over and over again."

Large earthquake faults also cut through the volcano, he said, making this zone even weaker and more dangerous. The torrential rain lubricated this brittle material on top of the volcano and a side of the mountain broke off, traveling for about 2 miles until it stopped at the base of a steep slope on the volcano, blocking a valley. "The side of the volcano just came crashing down, making a big, soggy pile at the bottom of the valley," Sheridan said. The water continued to accumulate there until it broke through one side of the valley, unleashing a kind of earthly tidal wave that deluged the villages.

Sheridan said the story of the devastation is written in the barren landscape where the two villages once stood and in the remembrances of a few eyewitnesses who still cannot believe what they lived through.

A report issued by the scientific team recommends that the area, settled only in the past several decades to develop sugar-cane farms, not be redeveloped for human habitation.