  We study holographically the out of equilibrium dynamics of a finite size
closed quantum system in 2+1 dimensions, modelled by the collapse of a shell of
a massless scalar field in AdS4. In global coordinates there exists a variety
of evolutions towards final black hole formation which we relate with different
patterns of relaxation in the dual field theory. For large scalar initial data
rapid thermalization is achieved as a priori expected. Interesting phenomena
appear for small enough amplitudes. Such shells do not generate a black hole by
direct collapse, but quite generically an apparent horizon emerges after enough
bounces off the AdS boundary. We relate this bulk evolution with relaxation
processes at strong coupling which delay in reaching an ergodic stage. Besides
the dynamics of bulk fields, we monitor the entanglement entropy, finding that
it oscillates quasi-periodically before final equilibration. The radial
position of the traveling shell is brought into correspondence with the
evolution of the entanglement pattern in the dual field theory. The
entanglement entropy is not only able to portrait the streaming of entangled
excitations, but it is also a useful probe of interaction effects.
