  We use numerical simulations with hydrodynamics to demonstrate that a class
of cold fronts in galaxy clusters can be attributed to oscillations of the dark
matter distribution. The oscillations are initiated by the off-axis passage of
a low-mass substructure. From the simulations, we derive three observable
morphological features indicative of oscillations: 1) The existence of
compressed isophotes; 2) The regions of compression must be alternate (opposite
and staggered) and lie on an axis passing through the center of the cluster; 3)
The gradient of each compression region must pass through the center of the
cluster. Four of six clusters reported in the literature to have cold fronts
have morphologies consistent with the presence of oscillations. The clusters
with oscillations are A496, A1795, A2142, and RX J1720.1+2638. Galaxy clusters
A2256 and A3667 are not consistent so the cold fronts are interpreted as group
remnants. The oscillations may be able to provide sufficient energy to solve
the cooling-flow problem and, importantly, provide it over an extended
duration.
