Deformation rates at volcanoes vary enormously, potentially altering the way in which volcanic rock accommodates strain. However, relationships between deformation rate, damage patterns, and physical properties are poorly understood. Laboratory deformation experiments are typically restricted to low strain rates ( ≪ 1 s −1 ). Here, we deformed samples of porous andesite in compression at strain rates from 10 −6 to ∼ 370 s −1 . We show, using X-ray computed microtomography, that the failure mode changes as a function of strain rate: macroscopic fractures form at low strain rates and samples deformed at high strain rate ( ≥ 100 s −1 ) contain macroscopic fractures and collapsed pores. In general, high strain rate deformation results in more pervasively damaged samples. Deformation at high strain rate also results in larger decreases and increases to P-wave velocity and permeability, respectively. Strikingly, the change in the P-wave velocity of samples deformed at high strain rate is very large (decreases of up to 50%). We hypothesize that faster events (e.g., explosions) can shatter the adjacent host rock, which could destabilise the volcano and encourage mass wasting events, increase the efficiency of outgassing by increasing permeability, and increase the ash content of plumes that accompany Vulcanian explosions.