The geothermal area Krýsuvík is situated on the Reykjanes peninsula in Iceland. It is in the south of Reykjanes in the middle of the fissure zone on the Mid-Atlantic Ridge which traverses Iceland.
Krýsuvík consists of several geothermal fields, such as Seltún. Here solfataras, fumaroles, mud pots and hot springs have formed, the soil is coloured bright yellow, red, and green hues. Sulphur deposits were mined in 1722 – 1728 and in the 19th century. German scientist Robert Bunsen visited the site in 1845 and, based on research there, proposed a hypothesis on formation of sulphuric acid in nature.
Near the geothermal fields are several maars – craters created by the explosions of overheated groundwater. The unusual green-blue Grænavatn lake has formed in one of these maars. Test boreholes were made here in the early 1970s, some of the boreholes have turned into irregular, artificial geysers, one of which exploded in 1999, leaving a crater.