When Did Hengill Last Erupt?
Learn more about the volcano in our backyard 🌋
The home of the Hellisheiði Geothermal Power Plant is the Hengill Volcanic System, which is part of the Reykjanes Volcanic Belt. This volcanic system makes it possible for ON Power to harness the earth’s heat to produce electricity and hot water. It has erupted several times throughout Iceland’s history, and our visitors often ask when it last erupted – and when it will erupt next.
Some geologists include the Hrómundartindur and Grændalur/Hveragerði volcanoes as parts or predecessors of the Hengill System, and together the three span an eruptive history of over 900,000 years. The Hengill System has erupted 9 times over the last 10,000 years.
The two most recent extrusive eruptions occurred approximately 5800 and 1900 years ago (~3750 BCE and 150±75 CE). They took place on 20 and 27 km long fissures, respectively. The lava flows from both eruptions cover an area of around 30 km2 each and are known as Hagavíkurhraun and Nesjahraun. During the most recent eruption, phreatomagmatic activity occurred in Lake Þingvellir. This is when magma and water interact, causing explosive eruptions. This activity formed two interlocking tephra rings on the island of Sandey.
The most recent activity in Hengill occurred in 1789. This was a magma intrusion, but no extrusive eruptive activity was observed. Heat from this intrusion contributes to the overall geothermal potential in the area.
When thinking about the next potential eruption in the Hengill System, it is impossible to predict when it will occur. It could be in the next 100 years or the next 5,000. Luckily, the area is heavily monitored, and we would have plenty of advance notice before any potential event. Working in active volcanic areas and high-temperature fields is necessary to harness enough energy to produce electricity, which is why it is important to understand these systems and monitor them accordingly.