Krafla Geothermal Station

Exploratory drilling at the Krafla area marked the beginning of the Icelandic state's construction work in 1974. Still, drilling boreholes and the powerhouse construction started in the summer of 1975. The Krafla Geothermal Station began generating electricity in 1978, with only 7 MW relayed to the country’s grid (Landsnet). Since 1999, the Krafla Geothermal Station has operated two turbine units, generating 60 MW, but the installed capacity is 500 GWh annually.

Landsvirkjun took over operations at the Krafla Geothermal Station in 1986. In 2022, a milestone was reached when the reinjection of run-off water into the geothermal tank was started, supporting the system's sustainability.

Landsvirkjun took over operations at the Krafla Geothermal Station in 1986.

Krafla Geothermal Station utilises geothermal steam from 18 boreholes to drive two 30 MW turbines. The processing areas in the mountainside are Suðurhlíðar, Hveragil, and Leirbotnar. The areas cover only approximately 2 km. High-temperature boreholes at Krafla Geothermal Station are 44, and most are located at Vítismór, Leirbotnar, and south of Mt. Krafla. Since 1997, directional drilling has mainly been used at the Krafla Geothermal Station. This drilling method results in higher costs than vertical drilling. Still, it lessens the environmental impact as more than one borehole is drilled from the same bore, leading to a smaller area being disturbed, and the access to the boreholes is limited to fewer bores.

Three eruptive phases have characterised historical time: the Dal Fires in Hlíðardalur, south of Mt. Krafla around the year 1000, the Mývatn Fires, lava flowing to Lake Mývatn and the formation of the main crater called Víti, from 1724 to 1729, and the Krafla Fires from 1975 to 1984.

Mývatn Fires

The Mývatn Fires started in 1724. An explosive eruption formed the main crater Víti. In August 1727, lava eruptions began, involving four pulses lasting until June 1729. In 1746, or 17 years later, a small eruption started, which is classified as the Mývatn Fires.

Krafla Fires

The Krafla Fires started in December 1975 when the Krafla Geothermal Station was under construction. Increased seismic activity was monitored on the days leading up to the event. The eruption started close to the construction area.

The Krafla Fires started in December 1975.

Lava flowed in nine phases from 1976 to 1984. However, large-scale magma movement occurred underground, as evidenced by the considerable earthquake activity. Lake Skjálftavatn in Kelduhverfi was formed from this seismic activity. The eruption induced significant ground sinking, and when it stopped, the magma continued to flow into the magma chamber, resulting in ground uplift. Lava from the Krafla Fires covers over 60 km² with a volume of 250 million m².

The construction of the Krafla Geothermal Station was a highly intricate and multifaceted endeavour, particularly given that an eruption started shortly after construction work began.

The Krafla Fires and the subsequent construction of the Krafla Geothermal Station were pivotal in advancing scientific knowledge on volcanic eruptions and the area's geology. The volcanic activity and ensuing research led to discoveries in the activity of central volcanoes and the phenomenon of magma located on the boundaries of the tectonic plates approaching the surface and erupting in isolated units called a volcanic system. This was coined magma intrusion, a new term in geoscience. The research added greatly to the understanding of the form and nature of the Krafla geothermal system.

A map of the area north of Lake Mývatn demonstrates its various types of lava in different colours.

The methods and experience gained from drilling and research at the Krafla area have significantly aided geothermal exploration and the preparation for new high-temperature geothermal power stations in Iceland. This is particularly true for technology involving drilling techniques, lining of the boreholes, and inspection of geothermal areas. The most important knowledge gained from harnessing the geothermal power of Krafla is the understanding that each geothermal area has its unique properties, behaviour, and utilisation features. The activity of the Krafla Fires shed light on various factors that were little or not known.