[Frontier Letter] Salt shell fallout during the ash eruption at the Nakadake crater, Aso volcano, Japan: evidence of an underground hydrothermal system surrounding the erupting vent
Interaction of magmatic-hydrothermal systems often controls styles and evolution of volcanic activities. Shinohara et al. (2018) revealed continuous existence of a hydrothermal system beneath the crater floor even during magmatic eruptions based on observations of a variety of salt fallouts at Aso volcano, Nakadake crater. Fragile hollow structure of salt fallouts observed during magmatic ash eruption in 2015 indicates their formation by the heating of hydrothermal solution droplets suspended by the erupting column, implying a hydrothermal solution pouring into the erupting vent at very shallow depth. The close distribution of the hydrothermal system surrounding the erupting conduit is likely a key condition of phreatomagmatic eruptions. Advancement of our knowledge on Aso volcano: Current activity and background."