The relatively small explosive eruption of Iceland’s Eyjafjallajökull volcano more than two years ago focused attention on the hazards of volcanic ash to aviation like no other event because of the extreme cost and prolonged disruption to millions of travelers,
The relatively small explosive eruption of Iceland’s Eyjafjallajökull volcano more than two years ago focused attention on the hazards of volcanic ash to aviation like no other event because of the extreme cost and prolonged disruption to millions of travelers, businesses, and the aviation industry. If you weren’t directly affected by Iceland ash, you probably knew someone who was.
Some of the volcanic ash erupted from Eyjafjallajökull was blown by winds over parts of Europe. To prevent any aircraft from encountering ash in flight, more than 100,000 flights were cancelled and more than 300 European airports closed, stranding 7 million passengers and causing $1.7 billion in loss of revenue to airlines.
Volcanic ash — angular rock and mineral fragments, less than 2 millimeters in diameter, ejected into the atmosphere during explosive eruptions — is a known hazard to aviation; there have been 79 damaging encounters of aircraft with ash clouds through 2009, resulting in abrasion, contamination of hydraulics and electrical systems, and in-flight engine shutdowns (for summary of incidents, see http://pubs.usgs.gov/ds/545/).
In July 2010, an International Volcanic Ash Task Force was created by the International Civil Aviation Organization (ICAO) to look at how best to manage air traffic in the vicinity of ash clouds and how best to describe and send out warnings of hazardous airspace. The U.S. Geological Survey (USGS) has long been involved in ash-hazard issues, and several USGS scientists participated in the Task Force.
The task force completed its work in June 2012 and published a final report (http://www.icao.int/safety/meteorology/ivatf/Lists/Meetings/AllItems.aspx). Most of the recommendations call for improvements in identifying and forecasting volcanic ash clouds with emerging technologies and capabilities.
A key issue that the task force investigated was determining the best method to depict zones of hazardous airspace. During the Eyjafjallajökull event, ash-concentration charts derived from computer dispersion models were introduced for use in Europe. The charts showed forecasted areas of airspace with low ash concentrations (less than about 2-4 milligrams per cubic meter). The hope was that, with accurate charts of forecasted ash concentrations, aircraft could fly through the dilute ash clouds without immediate safety impacts.
But the effort was not fully successful. The ash-dispersion computer models used to forecast ash concentrations downwind of an erupting volcano were found to have large uncertainties, as much as plus or minus tenfold.
This level of uncertainty is too large to identify ash concentrations with the level of confidence needed by the aviation industry to ensure safe flight operations. Based on consensus from scientific experts, the task force recommended that such charts not become standard warning products at this time.
The task force recommended, instead, that the world’s nine Volcanic Ash Advisory Centers (VAAC), which are charged with identifying ash clouds and forecasting their movement, use as many different observations as are available, in concert with computer models. These observations include quantitative satellite-based measurements, radar, lidar, airborne sampling, visual sightings by pilots, volcano observatory input, and any reported ash-aircraft encounters.
The task force also recommended stronger collaboration among the VAACs to identify and share best practices, thus eliminating needless differences in their procedures and products. They also considered timely notifications of volcanic activity by observatories important because warnings could be delivered even before an eruption started. USGS Volcano Observatories use a color-coded system to alert airlines and others of the status of a restless and erupting volcano.
In 2008, the USGS began issuing Volcano Observatory Notices for Aviation (VONA) to alert airline dispatchers, pilots, air-traffic controllers and others of activity that could produce ash clouds and of eruptions in progress (see VONAs at http://volcanoes.usgs.gov/activity/vonainfo.php). The color-code system and VONA have been recommended for use by Volcano Observatories worldwide by ICAO.
A key issue remains: whether aircraft can fly through dilute ash clouds safely — as airlines and engine manufactures claim — and, if so, for how long. Planning is underway in the United States for testing the performance of a modern jet engine ingesting ash at low concentrations for a few hundred hours of simulated “flight” time. Such a test is at least a year away. Look for an update in a future Volcano Watch.
Kilauea activity
update
A lava lake within the Halema‘uma‘u Overlook vent produced night-time glow that was visible from the Jaggar Museum overlook and by HVO’s webcam during the past week. Prolonged deflation and low lava levels early last week ended on Friday, Aug. 31, with inflation and lava level rise. Occasional rise-fall cycles caused the lava level to rise slightly for periods of hours.
On Kilauea’s east rift zone, deflation resulted in the formation of a new collapse pit during the past week on the north edge of Pu‘u ‘O‘o’s crater floor almost directly below the webcam. In addition, diminishing lava flows on the coastal plain and pali had stagnated by Saturday, Sept. 1. With the summit inflation over Labor Day weekend, breakouts reappeared on Sunday, Sept. 2, farther upslope, about 2.5 miles southeast of Pu‘u ‘O‘o. Lava levels within Pu‘u ‘O‘o rose with inflation, bringing lava in the northeastern pit within view of the webcams and filling the new northern pit.
No earthquakes were reported felt in the last week below the Island of Hawaii.
Visit the HVO website (http://hvo.wr.usgs.gov) for detailed Kilauea, Mauna Loa, and Hualalai activity updates, recent volcano photos, recent earthquakes, and more; call 967-8862 for a Kilauea summary; email questions to askHVO@usgs.gov.
Volcano Watch is a weekly article and activity update written by scientists at the U.S. Geological Survey‘s Hawaiian Volcano Observatory.
