New Risk Map for Planet's Riskiest Volcano Forecasts Far More Precisely Mudflow, Avalanche Dangers

BUFFALO, N.Y. -- A new risk map that reveals the hazards most likely to occur in the future on Popocatepetl -- located just 60 kilometers from Mexico City and considered the planet's riskiest volcano -- has been developed by University at Buffalo volcanologist Michael F. Sheridan, Ph.D., and colleagues at UB and the National University of Mexico (UNAM).

The map shows which areas will be in danger if a catastrophic event occurs at Popocatepetl and allows civil authorities in Mexico to make more informed evacuation decisions since it more precisely forecasts which areas an eruption's mud flows and avalanches are likely to reach.

The researchers decided to develop the map following the volcano's eruption last December, its most violent in historic times. Since then, Popocatepetal has continued to experience "sporadic, large eruptions," Sheridan said, and Mexican authorities are watching it closely.

According to Sheridan, Mexican researchers have state-of-the-art systems in place at Popocatepetl to monitor significant changes in what has been called the world's most monitored volcano.

"What's been missing is an equally advanced method of predicting just which populations actually will be in danger," he said.

A more accurate map became a critical priority, Sheridan said, following Popocatepetl's increased activity last winter.

"We've constructed these sorts of models after the event," said Sheridan. "But when you do that, people comment that, of course, you can correctly adjust the parameters after the event. But could you do it beforehand? So, from a humanitarian point of view, we decided we really wanted to make this forecast. We want to save as many people as possible."

After Popocatepetl erupted last December, Sheridan, along with UB geology professor Marcus Bursik; Bernard Hubbard, former Ph.D. candidate in the UB Department of Geology, and colleagues at UNAM, began using newly acquired digital topography to model the hazards the recent activity represents.

Digital topography represents topographic information by providing a grid of data points that specify elevation values for each individual grid area in the region being studied. Sheridan explained that the earlier hazard map of Popocatepetl was based on a grid spacing of hundreds of meters, a scale that omitted many important geologic features.

Data points now available and obtained from satellite data provided by NASA are separated by only 90 meters, a huge improvement, Sheridan said. He and Bursik now are working on new data points for Popocatepetl and other volcanoes separated by only tens of meters.

The improved resolution, however, results in a much larger dataset, making calculation of the flow paths and visualization of the data more time-consuming and far more demanding computationally.

To churn through all that data, the UB researchers use supercomputers at UB's Center for Computational Research.

"This new map is a major refinement," he said, in comparison to the 1995 hazard map of Popocatepetl that he and UNAM researchers developed. "We have been able to use actual volumes of flowing material to demonstrate different levels of damage, based on how violent the eruption is."

During the past six years, Popocatepetl has exhibited intermittent phases of activity, explosively ejecting gases and particles and then emitting only an occasional steam burst.

But December's active period was different, Sheridan said.

"Having red hot rocks thrown miles from the top of the volcano -- that hasn't happened in historic times," he said.

"It now has been more than 1,200 years since an eruption that seriously affected human habitation and that's what makes it a little scary," said Sheridan. "The volcano could go into a more dangerous phase at any time."

From field studies that include radiocarbon dating of samples taken from the mountain, scientists now know that catastrophic eruptions happen at Popocatepetl about every 1,000 years. The last large eruption that affected a population center is the one that occurred about 1,200 years ago Sheridan said, and products of that wiped out most of the area now occupied by Puebla, a city that is only 40 kilometers away, and is now home to about one million people.