Fracturing and tectonic stress drive ultrarapid magma flow into dikes

Abstract

Many examples of exposed giant dike swarms can be found where lateral magma flow exceeded hundreds of kilometers. We show that massive magma flow into dikes can be established with only modest overpressure in a magma body, if a large enough pathway opens at its boundary, and gradual build-up of high tensile stress has occurred along the dike pathway prior to onset of diking. This explains rapid initial magma flow rates, modeled up to about 7400 m3/s into a dike approximately 15-km-long, propagating under the town of Grindavík, SW-Iceland, in November 2023. Such high flow rates provide insight into the formation of major dikes and imply a serious hazard potential for high flow-rate intrusions that propagate to the surface and transition into eruptions.