Eyjafjallajökull volcano: A cloud on the horizon

The ash from Eyjafjallajökull volcano in Iceland continues to bring chaos to international travel. The eruption, which began on 14th April, shows no sign of diminishing. Scientists cannot forecast how long the eruption will last, but they note that the volcano’s previous outburst lasted for more than a year between 1821 and 1823. The prospect of another long eruption has focused attention toward economic gloom and despondency; passing virtually unnoticed is the fact that the system for warning about ash clouds has been an unqualified success.

Most of Europe has little experience in dealing with ash clouds and so its response depends on guidelines that have been developed elsewhere. The warning and response procedures are part of international protocols that evolved following the encounter in 1982 between a British Airways Boeing 747 and an ash cloud from Mount Galunggung in Indonesia. The aircraft lost power to all four engines and dropped four and a half miles (almost 25,000 feet) in 16 minutes before they could be restarted. It was agreed by the aviation community that the only way to minimise the loss or damage of aircraft was to alert pilots in a timely manner to divert flights around ash clouds. The volcanic ash aviation warning system was born, and the fact that flights in Europe were halted before any damaging encounters with the Eyjafjallajökull ash cloud demonstrates how well the warning system has worked.

So how does the warning system operate? Countries with volcanoes monitor volcanic activity via a dedicated observatory that uses a variety of techniques - from seismicity and ground movement to gas emissions and satellite observations - to evaluate when an eruption will occur and how its hazards may develop. Detecting whether a volcano is emitting ash can be tricky, especially if the volcano is remote, so satellite imagery is used to detect any thermal anomalies or ash plumes, as conventional radar techniques cannot detect ash particles.

Once a monitoring observatory has detected that a volcano is ejecting ash, it assigns an aviation colour code that ranges from green, yellow, orange to red, depending on the severity of the volcanic activity. This colour code is standardised throughout the world and is the tool that triggers the aviation and meteorological institutions to follow procedures set in place by the International Civil Aviation Organisation (ICAO). ICAO, along with the World Metrological Organisation (WMO), established the International Airways Volcano Watch (IAVW), which is responsible for dealing with volcano ash warnings from scientists. They have divided the world’s airspace into nine Volcanic Ash Advisory Centres (VAAC). The VAAC is part of the host country’s meteorological authority. In the current crisis, London is the VAAC in charge, and the VAAC is part of the UK Met Office. These centres are responsible for co-ordinating and disseminating information on volcanic ash to the aviation sector.

Together with the meteorological offices that normally provide weather reports to pilots, the VAAC and monitoring observatories continually review what is happening at the volcano and how the ash cloud is developing. Wind directions and speeds from weather forecasts are fed into sophisticated models that simulate where the ash cloud is travelling and dispersing. It is these models issued by the VAAC that have been seen on the news recently, showing the ash coverage over most of Europe in curious shapes driven by different winds at varying heights.

Since the Galunngung encounter in 1982, more than 80 serious incidents have been logged between commercial aircraft and volcanic ash clouds. These occurred as a result of inadequate warnings. The fact that none has occurred during the start of the Eyjafjallajökull eruption shows how effective a good warning can be.



Carina Fearnley
Aon Benfield UCL Hazard Research Centre
Department of Earth Sciences
University College London
Gower Street
London WC1E 6BT, UK. E: [email protected] T: +44 (0)20 7679 2452