Tracking Ash Clouds

Studying volcanoes by looking at changes in surface features falls into the category of long-term monitoring, which means that the study is done over a longer time period and doesn’t require the immediate availability of data. Short-term monitoring, on the other hand, demands a quick and rapid response, especially when the objective is to prevent or mitigate hazards.

Kenneson Dean, associate research professor at the University of Alaska’s Geophysical Institute, studies a unique hazard related to volcanic eruptions—one that didn’t concern Alaska until the rise of air traffic across the Bering Strait in the 1980s. The Alaskan skyway is one of the busiest air traffic areas in the world and, according to Dean, sometimes resembles a Los Angeles freeway. The skyway also runs along the northern boundary of the “Ring of Fire,” a zone of frequent earthquakes and volcanic eruptions that encircles the Pacific.

“Large-body jets fly across this region carrying about 2,000 passengers and $1 billion in cargo daily,” said Dean, who heads the satellite monitoring program at the Alaska Volcanoes Observatory (AVO) at the University of Alaska. “If a plane is flying towards an ash cloud, and the cloud is moving towards the plane, they will cross paths very quickly. Even if the cloud is not moving towards the plane, an aircraft still needs plenty of time to adjust its course and avoid the cloud.”

Jet engines operate at a temperature that melts volcanic ash or glass, and this melted material can then cause the engines to slow and shut down. “The problem in this area is that the eruptions tend to be explosive. They eject volcanic material, gas, and ash well into the atmosphere, and many of these eruptions rise to 40,000 feet (about 12,000 meters) in height, which is the height of jet air traffic,” said Dean. “A lot of people and property are at risk.”

The AVO uses satellite data for short-term monitoring, which means that data are received, processed, and analyzed just minutes after a satellite pass. “The region we monitor covers several thousand kilometers and includes about 40 volcanoes in Alaska and about 60 in the Kamchatka Peninsula, Russia,” Dean said. “We get the data directly from the MODIS and Advanced Very High Resolution Radiometer (AVHRR) sensors, and we analyze those data routinely every morning and afternoon.”

In 1993, the University of Alaska’s Geophysical Institute received a NASA grant to purchase its own AVHRR receiving station and, in 2001, a MODIS receiving station. Prior to having its own station, AVO used a Domestic Communications Satellite station at the University of Miami to collect the data and then send them electronically to Fairbanks for analysis. “Having our own stations on site reduced monitoring time from 1 hour to about 10 minutes,” said Dean. And minutes are important when you consider the hazard faced by aircraft that encounter ash clouds.

In 1982, a British Airways Boeing 747 carrying 240 passengers flew into an ash cloud near Indonesia’s Galunggung Volcano. All four of the aircraft’s engines shut down, nearly forcing the aircraft to ditch in the Indian Ocean. In 1989, a KLM 747 encountered an ash cloud over Talkeetna, Alaska. Again, all four engines failed and the jet descended to within a few thousand feet of the mountaintops before pilots were able to restart one of the plane’s engines and make an emergency landing in Anchorage.

Between 1980 and 1999, more than 100 jet airliners sustained some damage after flying through volcanic ash clouds, according to the U.S. Geological Survey (USGS). “Aviation safety is one big reason we need to monitor active volcanoes in Alaska,” said Dean. “Right now we’re seeing hot spots almost daily at Shiveluch, Kliuchevskoi, and Bezymianny Volcanoes. When an explosive eruption occurs, you need an information turnaround time that’s really fine-tuned, so that aircraft pilots have time to make decisions about whether to continue on their route, turn around, or change routes,” said Dean. “Available fuel becomes a critical issue, too.”

AVO’s short-term monitoring program is obviously making a difference. “When an eruption occurs and the warnings go out, the airline industry often contacts us directly,” said Dean. “We also follow Federal Aviation Administration reports, which reveal that aircraft are sometimes re-routed or even returned to their home port if the situation is bad,” said Dean.

Not all eruptions are explosive, like those that tend to occur in the Alaska region. Some volcanoes, such as those in the Hawaiian Islands, are known for more quiet flows of fluid lava. Although Hawaiian eruptions usually do not result in loss of life, they can have devastating effects on land and property.
 

Kilauea Volcano, on the island of Hawaii, is the most active volcano on Earth. During the past 1,000 years, more than 90 percent of the volcano’s surface has been covered by lava flows. Between 1983 and 1991, lava flows repeatedly struck communities located on the east coast of Hawaii. In 1990, flows covered the village of Kalapana, destroying more than 180 homes, a visitor center in Hawaii Volcanoes National Park, and historical and archaeological sites, according to the USGS.

“Hawaii volcanoes are known for long-term eruptions, wherein you have a small amount of gas emitted year in and year out for decades,” said Peter Mouginis-Mark, research scientist and current acting director at HIGP. Mouginis-Mark heads a HIGP-based program called Hawaii Synergy, a cooperative effort to provide disaster management organizations and federal hazard agencies with access to current satellite data, including imagery from Landsat 7 and the Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER), archived at the Land Processes Distributed Active Archive Center (LP DAAC).

According to Mouginis-Mark, perhaps the greatest benefit offered by satellite-monitoring technology will be an enhanced understanding of exactly how volcanoes work. “What’s important is the global perspective and the way volcanoes work on different timescales,” he said. “Some volcanoes produce lava flows, and other volcanoes explode so that you have to worry about big eruption columns. We now have this remote capability to study volcanoes anywhere in the world.”

Although scientists will continue to use ground-monitoring techniques to keep an eye on the Earth’s volcanoes, satellite data will increasingly allow scientists to see “the big picture” and, as a result, better predict volcanic activity.

“Satellite data are brilliant for understanding the levels of eruption intensity and for monitoring the impact an eruption is having on the surrounding environment,” said Mouginis-Mark. “The ability to draw on ASTER or MODIS data and put together a one- to three-year sequence of observations really lets us look at whether there are real changes going on in a volcano.”

“Compiling a global database of volcanic thermal unrest has allowed us to look at long-term trends,” said Wright. “We’re currently analyzing the entire MODVOLC data set to identify patterns that help us better understand how all the Earth’s volcanoes behave.”
 

References:
• Wright, R., L. Flynn, H. Garbeil, A. Harris, and E. Pilger. 2002. Automated volcanic eruption detection using MODIS. Remote Sensing of Environment. 82:135-155.
• T.P. Miller and Casadevall, T.J. Volcanic Ash Hazards to Aviation, in Encyclopedia of Volcanoes, ed. H. Sigurdsson. 2000. San Diego: Academic Press.
• The Pu’u ‘O’o-Kupaianaha Eruption of Kilauea Volcano, Hawai’i, 1983 to 2003. December 2002. USGS Fact Sheet. 144-02.

Links:
• MODVOLC: Global spaceborne thermal monitoring with MODIS. Accessed July 12, 2004.
• Alaska Volcano Observatory. Accessed July 12, 2004.
• Cascades Volcano Observatory (USGS). Accessed July 12, 2004.
• Hawaiian Volcano Observatory (USGS). Accessed July 12, 2004.