Volcanism of Iceland

The volcanoes of Iceland include a high concentration of active ones due to Iceland's location on the Mid-Atlantic Ridge, a divergent tectonic plate boundary, and its location over a hot spot.
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) and Snæfellsnes Volcanic Belt (SVB). Outside of the main island are the Reykjanes Ridge (RR), as part of the Mid-Atlantic Ridge to the southwest 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, comprising each volcano-tectonic fissure systems and many of them also a central volcano (mostly in the form of a stratovolcano, sometimes of a shield volcano with a magma chamber underneath). Thirteen volcanic systems have hosted eruptions since the settlement of Iceland in AD 874.
Of these 30 active volcanic systems, the most active is Grímsvötn. Over the past 500 years, Iceland's volcanoes have produced a third of the total global lava output.
Important eruptions.
"See also : List of volcanic eruptions on Iceland"
Laki/Skaftáreldar 1783-84.
The most fatal volcanic eruption of Iceland's history was the so-called Skaftáreldar (fires of Skaftá) in 1783–84. The eruption was in the crater row "Lakagígar" (craters of Laki) southwest of Vatnajökull glacier. The craters are a part of a larger volcanic system with the subglacial Grímsvötn as a central volcano. Roughly a quarter of the Icelandic nation died because of the eruption. Most died not because of the lava flow or other direct effects of the eruption, but from indirect effects, including changes in climate and illnesses in livestock in the following years caused by the ash and poisonous gases from the eruption. The 1783 eruption in Lakagígar is thought to have erupted the largest quantity of lava from a single eruption in historic times.
Eldfell 1973.
Eldfell is a volcanic cone on the east side of Heimaey which formed during an eruption in January 1973. The eruption happened without warning, causing the island's population of about 5,300 people to evacuate on fishing boats within a few hours. Importantly, the progress of lava into the harbour was slowed by manual spraying of seawater. One person died, and the eruption resulted in the destruction of homes and property on the island.
Eyjafjallajökull 2010.
The eruption under Eyjafjallajökull ("glacier of Eyjafjöll") in April 2010 was notable for causing enormous disruption to air travel across western and northern Europe over a period of six days in April 2010. About 20 countries closed their airspace to commercial jet traffic and it affected approximately 10 million travellers.
However this volcano is minor in Icelandic terms (VEI4) In the past, eruptions of Eyjafjallajökull have been followed by eruption of the larger volcano Katla, but after the 2010 eruption no signs of an imminent eruption of Katla were seen.
Grímsvötn 2011.
The eruption in May 2011 at Grímsvötn under the Vatnajökull glacier sent thousands of tonnes of ash into the sky in a few days, raising concerns of a repeat of the travel chaos seen across northern Europe.
Bárðarbunga 2014–2015.
Bárðarbunga is a stratovolcano and is roughly 2,000 metres (roughly 6,560 feet) above sea level in central Iceland (64.63°N / -17.53°W). This makes it the second highest mountain in Iceland.
The eruption series, Iceland's largest eruptions in 230 years that started on August 17, 2014 and lasted for 180 days, under the Bárðarbunga system started with an extremely heavy earthquake swarm followed by clusters of volcanic activity that went on for an extended period. This resulted in multiple lava fountain eruptions in Holuhraun. Lava flow was between 250 and 350 cubic metres per second and came from a dyke over 40 km long. An ice-filled subsidence bowl over 100 square kilometres in area and up to 65 metres deep formed as well. There was very limited ash output from this eruption unlike numerous glacial eruptions which are common in Iceland. The primary concern with this eruption was the large plumes of sulphur dioxide (SO2) in the atmosphere which adversely affected breathing conditions across Iceland, depending on wind direction. The volcanic cloud was also transported toward Western Europe in September 2014.
Fagradalsfjall 2021.
Following a three-week period of increased seismic activity, an eruption fissure developed near Fagradalsfjall, a mountain on the Reykjanes Peninsula. Lava flow from a 200-meter fissure was first discovered by an Icelandic Coast Guard helicopter on March 19, 2021 in the Geldingadalur area near Grindavík, and within hours the fissure had grown to 500 meters in length. This eruption suggests that more eruptions might start in different fissures once this eruption is over.
Structure of lava fields.
The smooth flowing basaltic lava pāhoehoe is in Iceland called "helluhraun". It forms rather flat surfaces that are quite easy to pass.
On the other hand, there is less flowing lava, ʻaʻā, on Iceland called "apalhraun". The loose, broken, sharp, spiny surface of an ʻaʻā flow makes hiking difficult and slow.