Krýsuvík (63° 53′ 34.3″N 22° 03′ 23.3″W), which is also called Seltún or Krýsuvík-Seltún, is a geothermal field. It shows different types of geothermal vents, like boiling hot springs and mud pots, as well as fumaroles and yellow sulfuric deposits. Rain and snow water circulates in earthquake fractures to depths of many kilometers, which is the main explanation of the geothermal fields at Krýsuvík (Guðmundsson, 2017). The water is acidified by accompanying gases such as hydrogen sulphide and carbon dioxide, which finally alters the rock to clay (www.geothermal.is).
Guðmundsson, Á. (2017). The glorious geology of Iceland’s Golden Circle. Springer. 334 pp.