From the Krafla eruption in 1980. Photo: Guðmundur Sigvaldason
Krafla in Northeast Iceland is one of Iceland’s most spectacular and active volcanoes. The prominent Hverfjall and Ludent tuff rings east of Lake Mývatn are the results of eruptions along the 100-km-long fissure system, which extends as far as the north coast of Iceland.

The renowned Mývatn formed during the eruption of the older Laxárhraun lava flow from the Ketildyngja shield volcano.

For nearly a decade the Krafla (map) caldera and Krafla fissure swarm erupted on and off in the period 1975-84. The events were a striking repetition of what happened during the Mývatn fires in the 1720s.

Mývatn is one of the most popular destinations in Iceland for foreign and domestic tourists. In 1975 an eruption started nearby. Nobody expected much activity and the fires were relatively contained. But they lasted until 1984.

The activity that took place there has been termed a rifting episode. It started with increasing seismic activity in the Krafla caldera during the second half of 1975, culminating with an earthquake swarm, ground fissuring, and a small lava eruption just north of Leirhnjúkur crater on December 20, 1975.

During an active episode, magma ascends below the central volcano and is stored in shallow magma chambers at a depth of 3 km. These events were accompanied by volcanic tremor, earthquakes swarms, vertical ground movements and widening of one part or other of the fissure swarm and increased geothermal activity. Some 17 volcanic events of this kind occurred from December 1975 until September 1984. After 1980 these events were accompanied by extrusion of lava.

The longer lasting eruptions started as long fissures but the activity concentrated after the first day on a short segment where sizeable scoria cones grew. After the September 1984 eruption the total area covered by the lava flows measured 36 square km and the volume about 0.25-0.3 km³.

Many feel that the current Holuhraun eruption reminds them of the Krafla fires.

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