Crystals creeping out of cracks.

Fig. 1. Behavior of condensates on smooth surfaces and within pores. The surface wettability determines the contact angle θ and the curvature of a liquid condensate on a smooth surface (A) and within a pore (B), where θ and the pore diameter strongly affect the liquid’s vapor pressure (C), here for the case of liquid water. Capillary condensation of a liquid (red) and subsequent crystal (green) nucleation and growth (D) for water and ice in a 10-nm pore (E).