Abstract At frequently erupting volcanoes, magma and volatiles ascend through established pathways, but the complete picture of their branching and supply system remains unclear. We integrated self‐potential (SP), broadband magnetotelluric (MT), and helium isotope observations to image magma and volatile pathways beneath Sakurajima Volcano. SP surveys delineate zones of groundwater flow and hydrothermal alteration, MT data reveal a columnar conductive zone (C1), and high 3 He/ 4 He ratios indicate magmatic volatiles. C1 is offset eastward and inclines northward with depth, coinciding with high 3 He/ 4 He locations. Active craters, pressure sources, and deep low‐frequency earthquakes align along edge of C1, supporting an edge‐ascent model in which magma and volatiles preferentially rise along conductor boundaries while volatiles branched at shallow level are laterally guided by shallow groundwater flow. Interpreting C1 as a large, long‐lived magmatic reservoir dominated by crystal mush, we propose that geodetically detected pressure sources represent small, transient magma pockets developing along its edges.
Aizawa et al. (Fri,) studied this question.