Abstract:

How do we constrain the rift and graben extension with partitioning between tectonics (i.e. non-magmatic faulting) and by igneous intrusions (i.e. diking)? Is rifting continuous or is diking and periodic opening of rifts the main process at play here? Extensional plate boundaries present certain challenges these days for Iceland with Grindavik costing over 80 Billion Icelandic Kroner and largely due to fault rupture and fissures (i.e. structural geology issues) impacting the built environment as well as lava barrier construction. However it also allows opportunities and the ongoing unrest in southwest Iceland provides new observations related to this system. A review of some recent graben forming and extensional events from the recent past from around the world in addition to those from 2023-present in Grindavík (e.g. De Pascale et al., 2024 - GRL), gives us first hand insight into graben formation and implications for tectonic and diking controls of both geological structures and subsequent control of volcanism. Diking certainly plays a role (e.g. Sigmundson et al., 2024 - Science), but can we decouple these to understand the systems better? The Grindavík case study, when compared with other regional and global events, gives us a rare 4D insight into extensional systems helps us explore the questions posed above in greater detail and sheds light on this important discussion which remains a major challenge in our understanding how plate boundaries operate.

References:

De Pascale, G. P., Fischer, T. J., Moreland, W. M., Geirsson, H., Hrubcová, P., Drouin, V., et al. (2024). On the move: 2023 observations on real time graben formation, Grindavík, Iceland. Geophysical Research Letters, 51, e2024GL110150.  

Freysteinn Sigmundsson et al.,Fracturing and tectonic stress drive ultrarapid magma flow into dikes. Science 383,1228-1235(2024). 

All are welcome.