Stanford expert says volcano danger to airliners hard to predict

By Jess McNally

Although many airlines have resumed flights to Europe after days of delays from Iceland’s volcanic ash cloud, they’ve had to do so without a clear measure of the risk, according to Stanford volcano researcher Darcy Ogden.

"Decisions to close or re-open the airspace are very challenging partly because they don’t have much data on which to base them," she says.

Ogden, a post-doctoral researcher in the Department of Geophysics, will give a public talk at Stanford on April 26 at noon entitled "Volcanic ash and the European air travel crisis." The talk will address the current eruption, previous incidents involving ash and aircraft, and how scientists are approaching the task of advising policy makers on airspace safety.

Ogden says there are two major challenges. The first is that while it is known that ash causes problems for jet engines and the exterior of planes, it is unclear how much ash it takes to cause those problems.

Volcanic ash melts inside engines and sticks to engine blades, which can cause them to fail. On the outside of planes, ash can abrade windshields and damage plane instruments. In both of these cases it is unclear how much ash is required to cause catastrophic problems.

The second major challenge is that "some ash is so fine that it is really hard to pick up directly by satellites, so it can be very difficult to track," Ogden said. Because they can’t see all of the ash from space, scientists must often rely on forecasting models to predict where the ash has moved.

The forecasting models used to track ash movement are much like the ones used by meteorologists to track weather or storms. "It’s a similar sort of physics and math that goes into them," Ogden said. But a big difference between storms and volcanic eruptions "is that storms happen a lot … so we’ve been able to verify and improve storm tracking models much more frequently."

The ash from this eruption is staying in the atmosphere for a few days, which means that scientists have to forecast its movement for multiple days. Ash conditions several days in the future become harder to predict, much like the seven-day weather forecast.

The 1821 eruption of Eyjafjallajokull lasted intermittently for more than a year, and also may have triggered the eruption of its larger neighboring volcano, Katla, which erupted a few months later. "The same volcano doesn’t always behave the same way twice," Ogden said, but it is possible that the volcano will continue to disrupt air travel for some time.

Ogden's primary interest is in understanding the inside of volcanoes to predict what they are going to do. She studies explosive volcanic eruptions using techniques originally developed for explosives and rocket design. During her talk on Monday, she will also describe other volcano science at Stanford aimed decreasing the risk posed by eruptions.

Her talk will be held at noon in the Hartley Conference Center in the Mitchell Building, 397 Panama Mall. It is sponsored by Stanford's Geophysics department and the School of Earth Sciences.

Jess McNally is an intern at the Stanford News Service.

-30-