Remote sensing of surface Hydrothermal Alteration, identification of Minerals and Thermal anomalies at Sveifluháls-Krýsuvík high-temperature Geothermal field, SW Iceland

This study used optical remote sensors to identify surface hydrothermal alteration and thermal anomalies in Krýsuvík geothermal field. Multispectral Landsat and ASTER satellite images were used to identify hydrothermal alteration minerals and thermal anomalies. A hyperspectral image from Hyperion was used for the analysis of absorption features. Spectral analysis from the visible (VIS) to the short wavelength infrared (SWIR) allowed the identification of possible sulfur, iron oxides, and montmorillonite. A time series analysis of thermal anomalies using the nighttime satellite images from 2002 to 2017 detected extinct surface hydrothermal activity southwest of the study area, and a thermal anomaly possibly affected by crustal deformation in the southeast. In Seltún area, thermal infrared (TIR) images acquired by a camera on an unmanned aerial vehicle (UAV) were compared with ground measurements; the aim was assessing the accuracy of the TIR images regarding the distance between the camera and the ground. The TIR image taken at 30 m elevation was used to calculate radiative heat flux; values were in same order of magnitude than the heat flux through the soil estimated by using ground measurements. This study provides insights for monitoring natural or induced changes on the surface geothermal activity of geothermal fields.