:The volcano system in Iceland that started activity on August 17, 2014, and ended on February 27, 2015, is Bárðarbunga.

:The volcano in Iceland that erupted in May 2011 is Grímsvötn.

thumb|220px|Active volcanic areas and systems in Iceland

thumb|220px|Volcanic and transform zones of Iceland

Iceland experiences frequent volcanic activity, due to its location both on the Mid-Atlantic Ridge, a divergent tectonic plate boundary, and being over a hotspot. Nearly thirty volcanoes are known to have erupted in the Holocene epoch; these include Eldgjá, source of the largest lava eruption in human history. Some of the various eruptions of lava, gas and ash have been both destructive of property and deadly to life over the years, as well as disruptive to local, European, and international air travel.

Volcanic systems and volcanic zones of Iceland

Holocene volcanism in Iceland is mostly to be found in the Neovolcanic Zone, comprising the Reykjanes volcanic belt (RVB), the West volcanic zone (WVZ), the Mid-Iceland belt (MIB), the East volcanic zone (EVZ) and the North volcanic zone (NVZ). Two lateral volcanic zones play a minor role: Öræfi volcanic belt (ÖVB also known as Öræfajökull volcanic system) and Snæfellsnes volcanic belt (SVB). Outside of the main island are the Reykjanes Ridge (RR), as part of the Mid-Atlantic Ridge to the south-west and the Kolbeinsey Ridge (KR) to the north. Two transform zones are connecting these volcano-tectonic zones: the South Iceland seismic zone (SISZ) in the south of Iceland and the Tjörnes transform zone (TFZ) in the north.

The island has around 30 active volcanic systems. Within each are volcano-tectonic fissure systems and many, but not all of them, also have at least one central volcano (mostly in the form of a stratovolcano, sometimes of a shield volcano with a magma chamber underneath). Several classifications of the systems exist, for example there is one of 30 systems, and one of 34 systems, with the latter currently being used in Iceland itself. There are 23 central volcanoes using the definition that they erupt frequently, extrude either basaltic, intermediate or felsic <!--reference used term acid which is long depreciated as vague by most volcanologists--->lavas, have an associated shallow crustal magma chamber, and are often associated with collapse caldera or fissure systems. Nearly thirty volcanoes are known to have erupted in the Holocene epoch and so are active.

Of these active volcanic systems, the most active is Grímsvötn. Over the past 500&nbsp;years, Iceland's volcanoes have produced a third of the total global lava output. Current productivity, which is known to be cyclical, has been estimated to be between per year which is higher than the output rate of the Hawaiian volcanoes, and would be double or even triple this figure if intrusive volumes are included.

  1. Spreading zones of rifting and volcanism producing the predominant Iceland tholeiitic basaltic crust
  2. Fracture zones connecting offset branches of the spreading zones which includes the SISZ
  3. Trans-tensional zones with transform faulting and spreading of which are the RVB and TFZ
  4. Flank zones with stratovolcanoes and minor rifting with alkalic to transitional volcanic rocks over the crust

These tectonic zones result from the interaction of combination of the spreading activity of the Mid-Atlantic Ridge which is spreading in a general east and west direction while the mantle plume activity that results in the hotspot, has been migrating over at least the last 25 million years in a west to slightly south-east direction. Where such eruptions interact with water the eruptions become more explosive and these phreatomagmatic eruptions produce tephra and possibly maars and tuff rings or cones. The compositional series are thus tholeiitic basalt, transitional alkalic basalts and alkalic (felsic). The island of Eldey off the south-west of the RVB has similar geological formations to the RVB but has a basalt composition with tholeiites and picrites. Hofsjökull, a large volcano with a caldera and rhyolite lavas in the MIB has explosive eruption potential but has not erupted underneath its ice cover for several thousand years and its companion Kerlingarfjöll for even longer.

Arc volcanism has been thought to be occurring in the Snæfellsnes volcanic belt with alkaline magma series volcanism in the stratovolcanoes such as Snæfellsjökull which usually erupt effusive basaltic lava but can have infrequent explosive silicic eruptions followed by extrusion of intermediate composition lava. However the modelling of the processes involved is incomplete and almost certainly involves primarily fractional crystallization of primary basaltic magma with limited input from pre-existing crustal material as is the case in arc volcanism. The ÖVB is represented by the Öræfajökull (Hnappafellsjökull) stratovolcano which has a history of violent rhyolite to alkali basalt eruptions with tephra volumes up to and accompanying jökulhlaup.

The island Vestmannaeyjar volcano to the southwest of Iceland has in its recent activity formed the island of Surtsey and cones such as Eldfell on Heimaey. It is the southern tip of the EVZ propagating rift in what is an off rift region called the South Iceland Volcanic Zone (SIVZ), and the older alkaline basalts were alkali olivine and more recent mugearite in composition. The basalts of the southern EVZ on land are rarely silicic but the volcanoes can have explosive phreatomagmatic eruptions.

Overall the surface area of post glacial erupted rocks of Iceland is 92% basalt, 4% basaltic andesites, 1% andesites, and 3% dacite-rhyolites.

Important eruptions

See also : List of volcanic eruptions in Iceland

Largest Holocene eruptions

Due to incomplete surveys, which also need to be confined to subaerial eruptions and not include igneous intrusions, the accumulative amounts of dense-rock equivalent erupted in Iceland will be underestimated.|name=LDRE !! Tephra DRE