Point chaud d'Islande

The Iceland hotspot is a hotspot which is partly responsible for the high volcanic activity which has formed the Iceland Plateau and the island of Iceland. Iceland is one of the most active volcanic regions in the world, with eruptions occurring on average roughly every three years (in the 20th and 21st century until 2010 there were 45 volcanic eruptions on and around Iceland). About a third of the basaltic lavas erupted in recorded history have been produced by Icelandic eruptions. Notable eruptions have included that of Eldgjá, a fissure of Katla, in 934 (the world's largest basaltic eruption ever witnessed), Laki in 1783 (the world's second largest), and several eruptions beneath ice caps, which have generated devastating glacial bursts, most recently in 2010 after the eruption of Eyjafjallajökull. Iceland's location astride the Mid-Atlantic Ridge, where the Eurasian and North American Plates are moving apart, is partly responsible for this intense volcanic activity, but an additional cause is necessary to explain why Iceland is a substantial island while the rest of the ridge mostly consists of seamounts, with peaks below sea level. As well as being a region of higher temperature than the surrounding mantle, it is believed to have a higher concentration of water. The presence of water in magma reduces the melting temperature, which may also play a role in enhancing Icelandic volcanism. There is an ongoing discussion about whether the hotspot is caused by a deep mantle plume or originates at a much shallower depth. Recently, seismic tomography studies have found seismic wave speed anomalies under Iceland, consistent with a hot conduit 100 km across that extends to the lower mantle. Foulger et al. believe the Icelandic plume reaches only to the mantle transition layer and can therefore not come from the same source as Hawaii. Bijwaard and Spakman, however, believe the Icelandic plume does reach to the mantle, and therefore comes from the same source as Hawaii.