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Abstract:
Vortex rings have been observed on volcanoes, since the eighteenth century. In fact, they have been seen at Etna (Italy), Redoubt (Alaska), Tungurahua (Ecuador), Pacaya (Guatemala), Eyjafjallajökull and Hekla (Iceland), Stromboli (Italy), Aso and Sakurajima (Japan), Yasur (Vanuatu), Whakaari (New Zealand) and Momotombo (Nicaragua). In this study we analyse the physical conditions under which volcanic vortex rings form. In order to better understand this phenomenon and provide clues on the dynamics of the volcanic vortex rings, we performed a series of finite element simulations to investigate which model configuration leads to the rings formation that best matches the field observations. Results show that the formation of volcanic vortex rings requires a combination of fast gas release from gas bubbles at the top of the magma conduit and regularity in the shape of the emitting vent. Our study is an important first step for the investigation of such complex phenomena and for the understanding of the very shallow degassing processes in magma conduits. Future experimental data may shed more light on such a fascinating process.
