Underwater and drone based photogrammetry reveals structural control at Geysir geothermal field in Iceland

Abstract

Geysers are local hydrothermal vents with periodic gas bubble driven explosions at the surface. Little is known, however, on the control on distribution, the dynamics and the geometry of the conduits of geysers. To better understand the link between the deep and surface expression at the Geysir geothermal field, Iceland, a detailed analysis of the spatial distribution of the thermal expressions, and their relationship to the tectonic framework was carried out. By use of high resolution unmanned aerial vehicle (UAV) based optical and radiometric infrared cameras, we are able to identify 364 distinct thermal spots distributed over the area. Close analysis of their arrangement yields a clustered appearance, following a preferred direction that is found to be consistent with the assumed tectonic trend in the area. Furthermore by using underwater cameras we are able to obtain for the first time detailed images from the two largest geysers at depths exceeding 20m. Near to the surface, the conduit of the geysers are near circular, but at a depth of 9–12m the shape changes into a crack-like elongated fissure. The elongation direction of these deep cracks is consistent with the identified thermal expression at the surface, highlighting a structural or even tectonic control at the Geysir geothermal field, which may also explain the susceptibility for seismically triggered activity changes.