We report in situ measurements of irradiation-induced creep on amorphous (a-) Cu56Ti38Ag6, Zr52Ni48, Si, and SiO2. Micropillars 1 mu m in diameter and 2 mu m in height were irradiated with similar to 2MeV heavy ions during uniaxial compression at room temperature. The creep measurements were performed using a custom mechanical testing apparatus utilizing a nanopositioner, a silicon beam transducer, and an interferometric laser displacement sensor. We observed Newtonian flow in all tested materials. For a-Cu56Ti38Ag6, a-Zr52Ni48, a-Si, and Kr+ irradiated a-SiO2 irradiation-induced fluidities were found to be nearly the same, approximate to 3 GPa(-1) dpa(-1), whereas for Ne+ irradiated a-SiO2 the fluidity was much higher, 83 GPa(-1) dpa(-1). A fluidity of 3 GPa(-1) dpa(-1) can be explained by point-defect mediated plastic flow induced by nuclear collisions. The fluidity of a-SiO2 can also be explained by this model when nuclear stopping dominates the energy loss, but when the electronic stopping exceeds 1 keV/nm, stress relaxation in thermal spikes also contributes to the fluidity. (C) 2015 AIP Publishing LLC.