In the North Volcanic Zone of Iceland, we studied with the greatest possible detail the complete structural architecture and kinematics of the whole Theistareykir Fissure Swarm (ThFS), an N-S-trending, 70 km long active rift. We made about 7500 measurements along 6124 post-Late Glacial Maximum (LGM) extension fractures and faults, and 685 pre-LGM structures. We have collected the data over the last 6 years, through extensive field surveys and with the aid of drone mapping with centimetric resolution. In the southern sector of the study area, extension fractures and faults strike mainly N10 •-20 • , the opening direction is about N110 • , and the dilation amount is in the range 0.1-10 m. In the central sector, faults and extension fractures strike mainly N00-10 • , the opening direction is N90-100 • , and the dilation amount is 0.1-9 m. In the northern sector, extension fractures and faults strike N30-40 • , the opening direction is about N125 • , and the dilation amount is 0.1-8 m. The variations in strike are attributable to two processes: the interaction with the WNW-ESE-striking Husavik-Flatey transform fault and Grímsey Oblique Rift (Grímsey lineament), and the structural inheritance of older NNE-to NE-striking normal faults. Most extension fractures show a minor strikeslip component: a systematic right-lateral component can be accounted for by the interaction with the WNW-ESE-striking fault zones and the regional, oblique opening of the rift. We regard dyke propagation as a possible cause for the more complex strikeslip components measured at several other fractures. Cumulated dilation and fracture frequency decrease along the rift with distance away from the Theistareykir volcano, situated in the central sector of the ThFS. This is interpreted as a decrease in the number of dykes that are capable of reaching great distances after being injected from the magma chamber.
In the present work, we demonstrate how drone surveys coupled with structure-from-motion (SfM) photogrammetry can help to collect huge amounts of very detailed data even in rough terrains where logistics can affect classical field surveys. The area of study is located in the NW part of the Krafla Fissure Swarm (NE Iceland), a volcanotectonic rift composed of eruptive centres, extension fractures, and normal faults. The surveyed sector is characterized by the presence of a hyaloclastite ridge composed of deposits dated, on a stratigraphic basis, to the Weichselian High Glacial (29.1–12.1 ka BP), and a series of lava flows mostly dating back to 11–12 ka BP. The integration of remotely sensed surveys and field inspections enabled us to recognize that this segment of the Krafla rift is made of grabens arranged en-échelon with a left-stepping geometry. A major graben increases in width in correspondence of the hyaloclastite cone; we interpret this geometry as resulting from the mechanical contrast between the stiffer lava succession and the softer hyaloclastites, which favours the development of concentric faults. We also measured a total extension of 16.6 m and 11.2 m along the fractures affecting the lava units, and a total extension in the hyaloclastites of 29.3 m. This produces an extension rate of 1.4 mm/yr in the Holocene lavas and 1.7 ± 0.7 mm/yr in the Weichselian hyaloclastite deposits. The spreading direction we obtained for this area is N97.7° E, resulting from the av. of 568 opening direction values.
Immersive virtual reality can potentially open up interesting geological sites to students, academics and others who may not have had the opportunity to visit such sites previously. We study how users perceive the usefulness of an immersive virtual reality approach applied to Earth Sciences teaching and communication. During nine immersive virtual reality-based events held in 2018 and 2019 in various locations (Vienna in Austria, Milan and Catania in Italy, Santorini in Greece), a large number of visitors had the opportunity to navigate, in immersive mode, across geological landscapes reconstructed by cutting-edge, unmanned aerial system-based photogrammetry techniques. The reconstructed virtual geological environments are specifically chosen virtual geosites, from Santorini (Greece), the North Volcanic Zone (Iceland), and Mt. Etna (Italy). Following the user experiences, we collected 459 questionnaires, with a large spread in participant age and cultural background. We find that the majority of respondents would be willing to repeat the immersive virtual reality experience, and importantly, most of the students and Earth Science academics who took part in the navigation confirmed the usefulness of this approach for geo-education purposes.
This work is aimed at reviewing the current state of the art in geosite selection, assessment, and communication. We first highlight the main papers that have defined paramount concepts such as geodiversity, geoheritage, and geosites. We then delve into the theoretical principles and guidelines that have been proposed over the last twenty years by researchers who have thoroughly illustrated how to individuate and assess geosites. In doing so, we illustrate notable field examples of applications of qualitative and quantitative assessments of geosites in places such as Serbia, India, Iceland, Ecuador, Sardinia (Italy), Egypt, Tasmania (Australia), and Brazil. The third part of this work is dedicated to illustrating a list (by no means exhaustive) of works that have tried to come up with innovative tools, strategies, and solutions to promote and communicate geosites. From our work, it appears that geosites can be extremely effective as fully fledged outreach tools capable of bridging the gap between Earth science and the lay public.
Abstract. We collected drone data to quantify the kinematics at extensional fractures and normal faults, integrated this information with seismological data to reconstruct the stress field, and critically compared the results with previous fieldwork to assess the best practice. As a key site, we analyzed a sector of the northeast rift of Mt Etna, an area affected by continuous ground deformation linked to gravity sliding of the volcano's eastern flank and dike injections. The studied sector is characterized also by the existence of eruptive craters and fissures and lava flows. This work shows that this rift segment is affected by a series of NNE- to NE-striking, parallel extensional fractures characterized by an opening mode along an average N105.7∘ vector. The stress field is characterized by a σHmin trending northwest–southeast. Normal faults strike parallel to the extensional fractures. The extensional strain obtained by cumulating the net offset at extensional fractures with the fault heave gives a stretching ratio of 1.003 in the northeastern part of the study area and 1.005 in the southwestern part. Given a maximum age of 1614 CE for the offset lavas, we obtained an extension rate of 1.9 cm yr−1 for the last 406 years. This value is consistent with the slip along the Pernicana Fault system, confirming that the NE rift structures accommodate the sliding of the eastern flank of the volcano.
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