Geothermal exploration in Graendalur valley, Hveragerdi, S-Iceland

Abstract

Geothermal mapping was conducted in Graendalur valley, which is located north of Hveragerdi town, South Iceland. The area is at the eastern margin of the Western Volcanic Zone (WVZ) and the South Iceland Seismic Zone (SISZ). The geothermal activities are related to the SISZ and the older part of Hengill central volcano (Hveragerdi volcanic system). The scope of this study was to map all surface geothermal manifestations, alterations, soil temperatures, and the emission of CO2 from the ground in order to examine the relationship between geothermal manifestations and structures. Then the results were compared with previous works in 1995 and 2009 to know whether changes occurred after the earthquakes in 2008. During the survey more than 217 geothermal manifestations were documented and 81 CO2 and soil measurements took place. The geothermal manifestations mapped are fumaroles/steam vents, mud pools, warm to hot springs, warm to steaming grounds and mineral precipitations. The results show the presence of thermal fluid circulation near the surface. Thermal fluid movement is governed by sub surface structures trending NESW, N-S and NW-SE. The earthquake in 2008 formed some new geothermal activity and increased the existing activities. In the Graendalur valley new activities are still occurring.