Gunnuhver (63°49’6.28″N 22°41’14.46″W) is a geothermal active field east of Bæjarfell. It is a small geothermal field with lots of steam and boiling mudpots. The largest mudpot of Iceland belongs to Gunnuhver. The Reykjanes Geothermal Power Plant uses this geothermal field to produce 100 MW of electricity with 12 wells, whose bottom temperatures are around 300°C at a depth of 2700 m (Guðmundsson, 2017). The groundwater at Gunnuhver consists to 100% of seawater. Carbon dioxide and hydrogen sulfide, accompanied gases, make the water acidic and alter the fresh lavas to clay. Throughout the entire hydrothermal field, evaporites and sulfuric minerals are visible. Metal ores, like copper sulfates, are more concentrated at depths. Steaming of the ground increased at Reykjanes, due to the pressure drawdown in the geothermal reservoir by the exploration, which started in 2006. The name Gunnuhver refers to the witch Guðrún, who caused a great disturbance until Eiríkur Magnússon, a priest at Vogsósar, set a trap that made her fall into the spring (www.geothermal.is).
Guðmundsson, Á. (2017). The glorious geology of Iceland’s Golden Circle. Springer. 334 pp.