Together with their collaborators at UNAM, the National University of Mexico, they presented their newest hazard map, developed for the volcano Pico de Orizaba, Mexico's highest mountain, Thursday in Mexico City.

This is the third such hazard map of a Mexican volcano developed by Michael F. Sheridan, UB professor of geology and principal investigator, and colleagues using computer simulations of volcanic phenomena.

It was developed by applying advanced remote sensing techniques that allow scientists to identify weak zones in the volcano's surface.

Hazard maps are a primary tool of government agencies in determining how to plan for potentially dangerous geologic events, but relying primarily on traditional methods such as fieldwork to construct them is extremely time-consuming and expensive.

By combining state-of-the-art technologies with computer simulations that illustrate where and how past eruptions and mudslides occurred at the volcano, scientists are able to much more quickly and accurately get detailed hazard maps into the hands of the officials charged with keeping their citizens safe.

Developed in close connection with local civil protection authorities, the hazard map for Pico de Orizaba provides the Mexican government, local authorities and the general population with the first detailed look at which communities could be affected by a variety of events at the volcano, ranging from landslides and mudflows to full-scale eruptions.

The nearest large city to Pico de Orizaba is Vera Cruz, which has a population of nearly two million and is located just 60 miles from the volcano.

The map was developed based on extremely detailed data gathered by remote sensing using advanced spectral sensing technologies.

While previous maps of the volcano were limited to displaying only "worst case" types of events, this one reveals three levels of hazard, based on their probability -- those that are the most frequent, most dangerous, and which occur nearest to the volcano's crater; less frequent but larger events, and the largest, least frequent and least dangerous events, which would impact populations furthest from the crater.

"This map confirms that we are very close to our goal of automating the process of making hazard maps," said Sheridan.

"We have shown we can develop these maps in a relatively short period of time using relatively few resources," he said.

Funded by NASA, Sheridan and Bernard Hubbard, former UB doctoral candidate, and their colleagues at UNAM, led by Dante Moran, used a NASA-developed technology called AVIRIS (Airborne Visible/Infrared Imaging Spectrometer) to detect remotely altered rock and other potentially dangerous features on volcanoes that cannot be detected easily through traditional fieldwork.

The sensors are located on a small airplane and collect extremely detailed data, 224 channels of spectral data for every pixel, representing a 100-yard square on the ground.

The technology has allowed the UB researchers to develop an incredibly detailed, and previously unavailable, picture of the stability -- or instability -- of a volcano's surface.

"When we use our eyes to look at the earth's surface, we are seeing only within a very narrow range of the visible spectrum," explained Sheridan. "But every mineral reflects its own unique spectrum of peaks and valleys that allow us to detect key mineral signatures in the infrared spectrum or beyond."

Until very recently, standard remote sensing technologies could only provide such geologic signatures in very general terms because data was only coming back in seven broad channels, in a more restricted range.

By contrast, the hazard map for Pico de Orizaba is based on sensing technology that provides data simultaneously on 224 separate channels, an improvement so dramatic that Sheridan at first could barely believe the readings.

"I couldn't believe you could identify just a percent or two of clay in an area the size of a football field, for example, but it turns out that with this technology, you can," he said.

According to Sheridan, the presence of clay or sulfur-bearing mineral is a possible indication of a weak zone, an area that could potentially initiate a slide that could present a danger to local populations, especially in the event of a major rainstorm.

"These weak areas can lubricate the fractures that exist inside each volcano, potentially causing an event of major magnitude, such as causing a whole side of a volcano to just slide off, as happened at Mt. St. Helens," he explained.

The spectral data also revealed that in some cases at Pico de Orizaba, the rock has been completely altered by hot acid solutions that circulate throughout the volcano, potentially weakening areas deep within it, as well as at its surface.

While such discoveries sound alarming at first, Sheridan noted that they are deep rock alterations, probably present to some extent in all volcanoes; it is just that the technologies that allowed such a precise picture only recently became available.

"It's not that nature is surprising, it's that we are surprised when we discover another piece that helps to explain how it all works," he said. - By Ellen Goldbaum


[Contact: Ellen Goldbaum]

11-Jan-2002