Eruption
Eruption in the Eyjafjallajökull volcanic system
The volcanic plume from Iceland that has caused the unprecedented catastrophic disruption of air traffic and closure of the European airspace is due to an explosive eruptive phase that began at Eyjafjallajökull volcano on 14 April 2010 (Iceland). It is a continuation of the eruptive activity that began on 20 March 2010 at the Eyjafjallajökull volcanic system.
The first eruptive phase (20 March to 12 April) was characterized by emission of lava flows. After a short hiatus in eruptive activity a new set of craters opened up in early morning of 14 April under the volcano’s ice covered central summit caldera. This eruptive phase was preceded with a swarm of earthquakes from around 23:00 on 13 April to 1:00 on 14 April. Meltwater started to emanate from the ice cap in the early morning of 14 April and a volcanic plume was also observed. Series of vents along a 2 km long north-south oriented fissure were active, with meltwater flowing down northern and southern slopes of the volcano. An ash loaded eruption plume rose to more than 8 km height, deflected to the east by westerly winds. Jokulhlaups (floods of meltwater) reached the lowlands around the volcano with peak flow around noon on April 14, with destruction of roads, infrastructure, and farmlands. No fatalities were recorded as people had already been evacuated from hazardous areas. Tephra fall was observed in the southeast of Iceland. A second jokulhlaup/lahar emanated from the ice cap down the Markarfljot valley in the evening.
On 15 April the eruption plume reached mainland Europe with closure of airspace over large part of Northern Europe. On 16 and 17 April some variability occurred in seismic tremor and tephra generation, but overall the eruptive activity remains stable. Air space over large part of Europe continues to be closed. An ash-loaded plume rose to more than 8 km, with tephra fallout in inhabited areas around the volcano. Steady easterly winds that have prevailed since the onset of the explosive eruptive phase were replaced by northerly winds that are transporting the ash south of the volcano.
Airborne volcanic ash is a serious aviation safety hazard. In the past 20 years, more than 80 commercial aircraft have unexpectedly encountered volcanic ash clouds in flight. Commercial jetliners that have encountered volcanic ash plumes have had all engines fail, with several near-crashes. Abrasion to forward-facing surfaces, including cockpit windows, the leading edges of wings and control surfaces, engine cowlings, etc., threaten safety and require expensive repairs. In June 1982 a British Airways Boeing 747 flew into a volcanic cloud at about 11 km south of Jakarta from an eruption of Galunggung volcano, Indonesia. Airborne volcanic ash abraded the outside of the aircraft, melted as it passed through the jet turbines and coated internal parts, and caused complete loss of thrust. After descending to within a few hundred meters of the mountaintops on Java, the crew were able to restart all engines and make a safe landing, an incredible feat given the damage to the aircraft and the lack of knowledge regarding how to react in such a situation. The Galunggung event, together with several subsequent near-disastrous encounters between commercial airliners and volcanic clouds, highlighted the need for early detection and accurate forecasting of volcanic cloud dispersal patterns. In the 1990’s nine Volcanic Ash Advisory Centers (VAAC) were set up around the world to improve forecasts of the locations of ash clouds from volcanic eruptions and are responsible for coordinating and disseminating information on volcanic ash that may endanger aircraft that fly through the ash cloud formed from a volcanic eruption.
The University of Geneva is directly involved in volcanic risk assessment with many projects on the effects of volcanic ash at active volcanoes:
Volcanology and geological risk research group
Updates of the eruption can be found at:
http://www.earthice.hi.is/page/ies_Eyjafjallajokull_eruption?414,38
Reference to photo:
http://sites.google.com/site/iavceirscweb/eruptions/eyja
C. Bonadonna