GNGTS 2024 - Atti del 42° Convegno Nazionale

Session 1.2 GNGTS 2024 Dike-arrest vs dike-propagaton: new insights from the Younger Stampar erupton (13 th Century), SW Iceland N. Cort 1 , F. L. Bonali 1,2 , E. Russo 1,2 , K. Drymoni 1,3 , F. Pasquarè Marioto 4 , A. Gudmundsson 5 , A. Tibaldi 1,2 1 Department of Earth and Environmental Sciences, University of Milan-Bicocca, Milan, Italy; 2 CRUST-Interuniversity Center for 3D Seismotectonics with Territorial Applicatons, Chiet Scalo, Italy; 3 Earth and Environmental Sciences, Ludwig-Maximilians-Universität in Munich, Munich, Germany; 4 Department of Human and Innovaton Sciences, Insubria University, Como, Italy; 5 Department of Earth Sciences, Queen's Building, Royal Holloway University of London, Egham, UK. Unravelling the parameters that control dike arrest and dike propagaton in the shallow crust, and subsequently the associated dike-induced deformaton at the surface, is of paramount importance in volcanology. This is because dikes can select among many diferent paths towards the surface and either stall in the crust or, alternatvely, feed volcanic eruptons. In this work, we study two vertcal dikes exposed in the sea-clifs of the Reykjanes Peninsula (SW Iceland). Both dikes are associated with the Younger Stampar erupton (1210-1240 CE) and were emplaced in the same crustal segment, which includes lava fows and tuf layers. Although one of them fed a lava fow at the surface, the other dike, located at a distance of 30 m from the feeder, became arrested only 5 m below the surface of the actve rif zone without inducing any britle deformaton. Hence, this outcrop represents an ideal case study to investgate the factors that favor dike arrest versus dike propagaton, as well as the conditons that afect dike-induced britle deformaton. We collected detailed structural data on the dikes and identfed the stratgraphic sequence of the outcrop. We mapped the nearby crater rows of the Stampar eruptons and reconstructed a high- resoluton 3D model through drone images and Structure from Moton (SfM) techniques. These data became inputs for 2D Finite Element Method (FEM) numerical models, using the COMSOL Multphysics® sofware (v5.6), to explain mechanically the dike arrest and why there is no britle deformaton at the surface induced by the arrested dike. We tested the role of dike overpressure (P o = 2-4 MPa), the stfness (Young’s modulus) of the layers, and the presence of an extensional or a compressional tectonic stress feld.