  This work investigates the morphological stability of a soft body composed of
two heavy elastic layers, attached to a rigid surface and subjected only to the
bulk gravity force. Using theoretical and computational tools, we characterize
the selection of different patterns as well as their nonlinear evolution,
unveiling the interplay between elastic and geometric effects for their
formation.
  Unlike similar gravity-induced shape transitions in fluids, as the
Rayleigh-Taylor instability, we prove that the nonlinear elastic effects
saturate the dynamic instability of the bifurcated solutions, displaying a rich
morphological diagram where both digitations and stable wrinkling can emerge.
The results of this work provide important guidelines for the design of novel
soft systems with tunable shapes, with several applications in engineering
sciences.
