We explore the ion beam-induced dynamics of the formation of large features at the edges of nanopores in freestanding silicon nitride membranes. The shape and size of these “nanovolcanoes”, together with the rate at which the nanopores open or close, are shown to be strongly influenced by sample temperature. Volcano formation and pore closing slow and stop at low temperatures and saturate at high temperatures. Nanopore volcano size and closing rates are dependent on initial pore size. We discuss both surface diffusion and viscous flow models in the context of these observed phenomena.