  We argue that there are two mechanisms responsable for the growth of high
energy cross-sections - \sigma_{tot} and \sigma_{el}, say - in pp collisions.
One is by the increase of matter \emph{density}, resulting in the black disk
saturation. The other is by exclusively radial expansion affecting the
periphery of the overlap area. Within this simple model we can reproduce all
available data in pp from ISR to LHC. In order to achieve a fast growth in the
very high energy cosmic ray energies, we propose a fast black disk saturation
followed by the dominance of geometric scaling (GS).
