Stability of a sodium chloride indenter contact undergoing pressure solution

In situ observations of the contact between a halite indenter and a flat silicate plate immersed in saturated solution indicate that the indenter deforms in two sequential stages: the first involves rapid inward dissolution of the free faces around the edge of the contact accompanied by slow vertical convergence caused by vertical dissolution and the elastic response to the shrinking contact. The second stage consists of rapid vertical convergence by plastic flow complemented by removal of the flowed material by inward dissolution. The contact between the indenter and plate evolves into a dynamic network of steep channels and islands that moves about throughout the process. This study exhibits some of the advantages of confocal microscopy in observing dynamic processes.