EGU General Assembly 2020
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the Creative Commons Attribution 4.0 License.

Unravelling rift development: a key study from the Northern Volcanic Zone of Iceland

Elena Russo1,2, Alessandro Tibaldi1,2, Fabio Luca Bonali1,2, Federico Pasquarè Mariotto3, Páll Einarsson4, and Ásta Rut Hjartardóttir4
Elena Russo et al.
  • 1Department of Earth and Environmental Sciences, University of Milan-Bicocca, Milan, Italy
  • 2CRUST- Interuniversity Center for 3D Seismotectonics with Territorial Applications, Italy
  • 3Department of Human and Innovation Sciences, Insubria University, Varese, Italy
  • 4Nordic Volcanological Center, Institute of Earth Sciences, University of Iceland, Reykjavík, Iceland

Unravelling the kinematics, development and origin of the structures along a volcano-tectonic rift is of paramount importance for understanding plate separation, seismicity, volcanic activity and the associated hazards. Here, we focus on an extremely detailed survey of the Holocene deformation field along the Northern Volcanic Zone of Iceland, the northernmost point of emergence of the Mid-Atlantic Ridge. The study of this extremely dynamic rift is also useful for a better comprehension of how mid-oceanic ridges work. The study is based on extensive field and unmanned aerial vehicle surveys performed over the last four years, completed by about 6000 measures collected at 1633 sites on fault strike, dip and offset, and fracture strike, dip, dilation direction and dilation amount. The rift, named Theistareykir Fissure Swarm, is composed of N-S to NNE-SSW-striking normal faults and extension fractures affecting an area 8 km-wide and 34 km-long. The computed overall spreading direction is N111° averaged during Holocene times, with values of N125° to the north and N106° to the south. The kinematics is characterised by the presence of complex components of right-lateral and left-lateral strike-slip motions, with a strong predominance of right-lateral components along structures parallel and coeval to the rift zone. The surveyed 33 Holocene faults (696 sites of measurement) along the central part of the rift show two opposite directions of fault/rift propagation, based on fault slip profile analyses. We discuss the possible causes of these characteristics and analyse in detail the interaction of both faults and extension fractures with the WNW-ESE transform Tjornes Fracture Zone, and in particular with the parallel right-lateral Husavik-Flatey Fault in the central part of the rift, and the Grimsey Lineament to the north. We also assess the role of: i) repeated dyke intrusions from the magma chamber outward along the plate margin, ii) regional tectonic stresses, iii) mechanical interaction of faults, and iv) changes in the rheological characteristics of rocks.

How to cite: Russo, E., Tibaldi, A., Bonali, F. L., Pasquarè Mariotto, F., Einarsson, P., and Hjartardóttir, Á. R.: Unravelling rift development: a key study from the Northern Volcanic Zone of Iceland, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-500,, 2019

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Presentation version 1 – uploaded on 01 May 2020
  • CC1: Questions and answers from the live chat during EGU2020, Michael Heap, 11 May 2020

    Q: Your dataset seems somewhat unique. Are any other volcanic centres monitored this way?

    A: Thanks for the question. This dataset is the result of multiple years of field campaigns and of the combined approach between field data and data collected through Unmanned Aerial Vehicles (UAVs). This is an innovative approach that has not been applied elsewhere so far!

    Q: 6000 fracture measurements, well done! 20 degree difference in the northern part of the Theistareykir rift segment compared to its southern end, can you explain why?

    A: Thanks! So far, we believe that this rotation of fractures strike and clockwise rotation of opening directions is due to the interaction with the Grimsey Lineament which is part of the Tjornes Fracture Zone to the north of the Theistareykir Fissure Swarm.

    Q: What percentage of your fractures would be classified as faults and what as tension fractures?

    A: Thanks for your question! We have a 15% of normal faults and the rest can be classified as tension fractures.

    Q: Do you see a lateral component only on extension fractures or on mature faults also?

    A: Thank you for your question. In this study we focused in particular on measuring lateral components along tension fractures, lateral components along faults are to be investigated still!