The icecap of the glacier Eyjafjallajökull (meaning 'island mountain glacier') covers a volcano (1,666 metres or 5,466 ft in height) which has erupted relatively frequently since the last Ice Age.
The volcano erupted twice in 2010, on 20 March and 15 April.
The April eruption caused massive disruption to air traffic across Northern Europe and scientists claimed it was ten to twenty times more powerful than the March event.
The most recent eruption before 2010 was from 1821 to 1823, causing a fatal glacial lake outburst flood. A previous eruption was in 1612. The crater of the volcano has a diameter of 3–4 kilometres (1.9–2.5 mi) and the glacier covers an area of about 100 square kilometres (39 sq mi).