Volcanic ash from magma fragmentation harms infrastructure and the environment. While bubble expansion is key in fragmentation, low-intensity eruptions often produce ash with fewer bubbles. This study used tensional experiments on high-temperature silicate melt, observing fracture leading to small fragments. The fracture surface showed smooth and rough regions, similar to glass fractures at room temperature, with the rough region generating small fragments. Stress-strain curves indicated fragmentation occurred under viscous deformation, suggesting silicate melts fragment like glass at room temperature. Ductility near the crack tip promotes void nucleation and coalescence, generating dense, fine volcanic ash.
