  We study the dynamics of holes created in vertically vibrated dense
suspensions and viscous Newtonian liquids. We find that all holes oscillate
with the driving frequency, with a phase shift of $\pi/2$. In Newtonian liquids
holes always close, while in suspensions holes may grow in time. We present a
lubrication model for the closure of holes which is in good agreement with the
experiments in Newtonian liquids. The growth rate of growing holes in
suspensions is found to scale with the particle diameter over the suspending
liquid viscosity. Comparing closing holes in Newtonian liquids to growing holes
in dense suspensions we find a sinusoidal, linear response in the first, and a
highly non-linear one in the latter. Moreover, the symmetry of the oscillation
is broken and is shown to provide an explanation for the observation that holes
in dense suspensions can grow.
