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Cavernous weathering may be conceptualized as a self-reinforcing process, characterized by positive feedback within the weathering system. A morphometric study of caverns in the Valley of Fire State Park, Nevada, USA, demonstrates the applicability of a dynamically unstable, or conditionally unstable, model of cavernous weathering systems. Outcrop surfaces displaying caverns tend to show increasing fragmentation of the surface in the early stages of cavernous weathering, succeeded by convergent evolution of the surface in which caverns tend to grow and coalesce. A paradoxical relationship exists between the weathering system output at the scale of individual forms and the outcrop scale: caverns tend toward minimum interior surface area by developing a spheroidal form, yet the outcrop surface tends toward maximum exposed surface area by increasing the degree of fragmentation of the surface.

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Sandstones are widely used as building stones throughout NW Europe. Unlike limestone, sandstones tend to experience episodic and sometimes rapid surface retreat associated with the action of salts and often leading to the development of hollows/caverns in the stone. The unpredictability of these decay dynamics can present significant problems when planning conservation strategies. Consequently, successful conservation requires a better understanding of the factors that trigger decay and determine the subsequent decay pathway. An overview of results from previous studies provided the basis for simulation experiments aimed at identifying the factors that (a) initiate decay and (b) permit the continuance of salt weathering despite rapid loss of surface material. These simulation studies involve investigation of changes in micro-environmental conditions as surface hollows develop and examination of salt weathering dynamics within such hollows. These data combined with knowledge gained from previous work have allowed the refinement of a conceptual model of rapid sandstone retreat. In this model decay is linked to the establishment of positive feedback conditions through interactions between factors such as porosity, permeability, mineralogy and their effect on salt penetration.