Exploring Offshore Geothermal Fields Around Iceland

Abstract

The Icelandic waters hold a number of geothermal fields, both low and high temperature, but none of them are harnessed (Fig. 1). Majority of the known low temperature sites ( less than 100°C at 1 km depth) are hot springs found in the tidal zone all around Iceland. In recent years geothermal sites have been discovered farther out. The best-known are the Ystavík and Arnarnes vents in Eyjafjörður, N-Iceland, where rows of geothermal chimneys are connected to active fissures and faults. All these low temperature vents are issuing more or less fresh water. Several offshore high temperature areas have also been discovered. They are related to the rift zones and volcanic activity of the Reykjanes Ridge, Kolbeinsey Ridge and the Tjörnes Fracture Zone. They are: (1) The Kolbeinsey geothermal field, at around 100 m depth, 100 km off the north shore, near the islet of Kolbeinsey. (2) The Grímsey geothermal vent field, at 400 m depth east of Grímsey island. (3) The Eldey geothermal field, at 80-120 m depth, 12 km SW of Reykjanes. (4) The Steinahóll geothermal field, at 160-300 m depth near the insular shelf break, some 120 km SW of Reykjanes. The high temperature fields are all issuing hot brine. Because of the water pressure the seafloor boiling temperature is high. In the case of Grímsey vent field it is 250°C, similar to the core temperature of many onshore high temperature systems. Some areas are inferred geothermal fields because of indirect indications of geothermal activity such as, gas bubbles on sea surface, geothermal altered material in core section, geothermal precipitates recovered from trawls and melted nylon trawls. Further mapping and exploration of the oceanic floor around Iceland in the coming years will certainly lead to discovery of unknown geothermal fields. Utilization of offshore geothermal energy might be possible in the future and the first steps have already been taken in that direction.