When a block of solid caramel tilted from the horizontal is put in a water bath, patterns are observed underneath the block. The dissolved caramel is denser than water. It results in a buoyancy-driven instability of the dissolution flow, a local variation of the solute concentration in the vicinity of the surface, and finally a differential dissolution of the solid. The longitudinal stripes observed at short times (t=10s) interact with the flowing caramel and evolve: the stripes cross and form chevrons (t=10min). Then chevrons open, which leads to scallops (t=60min). The typical size of caramel scallops is 5mm.
The same patterns as in our lab experiments appear on icebergs underwater. The freshwater due to the melting of the iceberg is less dense than the surrounding sea saltwater. The flow upward induces variations of salt concentration or temperature, which influences the melting of ice and shapes its surface. The typical size of iceberg scallops is 20cm.