Expulsion of incandescent pyroclasts of >64 mm from active volcanoes are known as 'volcanic bombs'1-3, which can pose significant hazards to life and manmade structures. Most volcanic bombs are considered to fall ballistically, enabling the prediction of a volcanic hazard radius4,5. Here we describe a bomb type that was ejected ballistically, but subsequently travelled downslope a steep volcanic flank, posing an important but hitherto unrecognized impact and fire hazard. The volcanic bombs were

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... observed to fall from the summit of the newly formed La Palma cone in late October 2021 and fell on a soft tephra substrate, travelling downhill for over a kilometer in some instances. The bombs spalled incandescent lava fragments en route, creating a significant fire hazard far beyond the range of ballistic transport. Spallation bomb hazards ought to be considered in volcanic risk assessment, necessitating an increase of hazard radius exceeding a factor of two on steep-sided volcanoes with ballistic bomb activity.