The 2010 eruption of Eyjafjallajökull were volcanic events at Eyjafjallajökull in Iceland which, although relatively small for volcanic eruptions, caused enormous disruption to air travel across western and northern Europe over an initial period of six days in April 2010. Additional localised disruption continued into May 2010. The eruption was declared officially over in October 2010, when snow on the glacier did not melt. From April 14–20, ash covered large areas of northern Europe when the volcano erupted. About 20 countries closed their airspace (a condition known as ATC Zero) and it affected more than 100,000 travellers. The grounding of European flights avoided about 3.44×108 kg of CO2 emissions per day, while the volcano emitted about 1.5×108 kg of CO2 per day.
Seismic activity started at the end of 2009 and gradually increased in intensity until on 20 March 2010, a small eruption started rated as a 1 on the Volcanic Explosivity Index.
Beginning on 14 April 2010, the eruption entered a second phase and created an ash cloud that led to the closure of most of the European IFR airspace from 15 until 20 April 2010. Consequently, a very high proportion of flights within, to, and from Europe were cancelled, creating the highest level of air travel disruption since the Second World War.