The 2010 eruptions 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 14–20 April, ash covered large areas of northern Europe when the volcano erupted. About 20 countries closed their airspace to commercial jet traffic and it affected about 10 million travellers.
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. The second phase resulted in an estimated 250 million cubic metres (330,000,000 cu yd) (0.25 km3) of ejected tephra and an ash plume that rose to a height of approximately 9 kilometres (30,000 ft), which rates the explosive power of the eruption as a 4 on the volcanic explosivity index. By 21 May 2010, the second eruption phase had subsided to the point that no further lava or ash was being produced.
By the evening of 6 June 2010, a small new crater had opened up on the west side of the main crater. Explosive activity from this new crater was observed with emission of small quantities of ash. Seismic data showed that the frequency and intensity of earth tremors still exceeded the levels observed before the eruption, therefore scientists at the Icelandic Meteorological Office (IMO) and the Institute of Earth Sciences, University of Iceland (IES) continued to monitor the volcano.
In October 2010, Ármann Höskuldsson, a scientist at the University of Iceland Institute of Earth Sciences, stated that the eruption was officially over, although the area was still geothermally active and might erupt again.