Description
This 3D model shows a 160m x 86m wide area, displaying extension fractures belonging to Theistareykir Fissure Swarm, in the Northern Volcanic Zone of Iceland. The fractures, with a maximum dilation up to 4 m (Mariotto et al., 2020), affect post-Last Glacial Maximum, horizontal lava units (8-10 ka BP; Saemundsson et al., 2012), of Holocene age. The shorter extension fractures, to the south, are parallel to each other, strike about N10° and show an about 0.3-0.5 m dilation; it is also possible to observe the overlapping between two fractures. The longer fracture reaches a maximum dilation of 5 m and strikes N-S, slightly rotated in an anticlockwise fashion to the others. All the structures cut basaltic lava flows and are the result of the extensional tectonic regime affecting the Northern Volcanic Zone of Iceland, where the overall spreading directions is about N106°, with an opening of about 2 cm/yr (Hjartardóttir et al., 2016). A close-up of the fractures reveal the tipycal zig-zag pattern of their borders, due to the columnar jointing of the lavas during cooling; piercing points can be clearly observed (Bonali et al., 2019).
The ground is characterized by periglacial morphologies covering the underlying basaltic lava flows; they are known as ‘pingo’, and are formed owing to the growth of ice lenses within the soil.

Credits: UAV-based surveys and 3D DOM by Fabio L. Bonali; funding is from MIUR project ACPR15T4_00098 (http://argo3d.unimib.it/). Description by Alessadro Tibaldi and Federico Pasquaré Mariotto.

References

  • Bonali, F. L., Tibaldi, A., Marchese, F., Fallati, L., Russo, E., Corselli, C., & Savini, A. (2019). UAV-based surveying in volcano-tectonics: An example from the Iceland rift. Journal of Structural Geology, 121, 46-64.
  • Hjartardóttir, R., Einarsson, P., Magnusdóttir, S., Bjornsdóttir, Þ. and Brandsdóttir, B. (2016) Fracture systems of the Northern Volcanic Rift Zone, Iceland: an onshore part of the Mid-Atlantic plate boundary. In: Wright, T. J., Ayele, A., Ferguson, D. J., Kidane, T., Vye-Brown, C. (eds), Magmatic Rifting and Active Volcanism. Geological Society, London, Special Publications, 420, 297-314.
  • Mariotto, F. P., Bonali, F. L., & Venturini, C. (2020). Iceland, an Open-Air Museum for Geoheritage and Earth Science Communication Purposes. Resources, 9(2), 14.
  • Saemundsson, K., Hjartarson, A., Kaldal, I., Sigurgeirsson, M.A., Kristinsson, S.G. and Vikingsson, S. (2012) Geological map of the Northern Volcanic Zone, Iceland. Northern Part 1: 100.000. Reykjavik: Iceland GeoSurvey and Landsvirkjun.