Advances in field data collection in volcano-tectonic sensitive areas: examples and results from the Northern Volcanic Zone of Iceland

Classical field studies are vital for mapping and understanding volcano-tectonic processes, particularly for those that produce superficial deformation consequently to magmatic and tectonic activity. Unfortunately, very often, key outcrops are inaccessible due to harsh logistic conditions or their location in remote or dangerous areas. In the framework of the ILP Task Force II, we developed and tested modern and innovative methods aimed at overcoming these limitations in field research and data collection, that we combined with classical field mapping. Such methods have been used to provide a more complete picture of the deformation processes that have been taking place in the Theistareykir Fissure Swarm within the Northern Volcanic Zone of Iceland. This rift is characterized by the presence of huge normal faults, several extension fractures and volcanic centres. The modern methods we used derive from the use of UAVs (drones) combined with Structure from Motion (SfM) photogrammetry techniques. The first innovative method consists of analysing UAV-based SfM-derived high resolution orthomosaics and digital surface models where we collected hundreds of quantitative measurements of the amount of opening and opening direction of Holocene extension fractures and measurements of fault scarp height. The second and more innovative method we used is the Immersive Virtual Reality that can be applied to 3D digital outcrop models (DOMs), reconstructed with UAV-based SfM photogrammetry techniques; several sites within the Theistareykir Fissure Swarm have been reconstructed in the framework of the Italian Argo3D project. The reconstructed 3D DOMs were explored using different modalities: on foot, as is often the case during field activity, moving like a drone, above and around the target, as well as flying like an airplane. Thanks to these modes of exploration we were capable of better understanding the geometry of extension fractures, volcanic centres and normal faults. We also measured, in the virtual environment, the opening direction and the amount of dilation along the extensional fractures, the direction of magma-feeding fractures underlying cones and volcanic vents, as well as the amount of vertical offset along normal faults. The quantification and mapping of these features was accomplished through some tools tailored for virtual field activity in the framework of Italian Argo3D project and the Erasmus+ Key Action 2 2017-1-UK01-KA203-036719. Thanks to the merging of classical and modern approaches we are able of providing a complete picture related to the post-LGM deformation field affecting this part of the Icelandic rift, particularly focusing on the spreading direction and the stretch ratio across the whole Theistareykir Fissure Swarm.