Abstract

Boiling mud ponds, hot springs, and geysers are the scenic surface expression of rising thermal fluids, often emerging in clusters. The details on the spatial appearance and structural control of such geothermal objects as well as on the variability of their locations are rarely investigated, however. Here we use Unmanned Aerial Systems (UAS) to acquire close-range optical and thermal infrared data over the El Tatio geothermal field (Chile), one of the largest geyser fields in the world. From high-resolution aerial images, processed using the Structure from Motion (SfM) method, we compute spatial image data at 1.5 to 14.5 cm resolution for a similar to 2 km(2) area. We identify 1863 objects related to geothermal activity, providing an unprecedented catalog of the geothermal area. Out of these, 148 were classified as topography objects (e.g. cone geysers), 415 showed signs of fluid discharge, and 1091 were characterized by a thermal signature exceeding background temperatures. The geothermal objects were further analyzed regarding their spatial distribution and clustering, suggesting a high degree of organization in 5 main groups on a broader scale, and clustering in specific vent arrangements resembling two main orientations on a smaller scale. The 5 zones show significant differences considering their orientation, types of geothermal objects located within, but also their eruptive characteristics, and thermal energy release. We discuss these, considering the structural setup and hydrological setting of the El Tatio geothermal field. Over 90% of the mapped geothermal objects are located within a 100 m distance to an estimated trend line oriented NE-SW. We thus hypothesize a possible structural arrangement controlling the location and activity of geothermal objects at El Tatio with important implications for other geothermal areas worldwide.