Experimental studies on the solidification of ammonium-chloride-water alloys in rel-
atively large containments reveal conditions that lead to the formation of numerous crystal ava-
lanches. Columnar segments that occasionally slide downwards along a vertical mushy zone
further fragmentate and so crystal multiplication occurs. As a condition for this phenomenon
solidification-induced solutal buoyancy that leads to a rising interdendritic flow was identified
for the present case. The interaction with sedimentation-induced downward flow ahead of a ver-
tical columnar region results in a redirection of the interdendritic flow and thus, to local condi-
tions that slow down further solidification or even lead to remelting. Gravity is then pulling loose
segments downwards. In larger containment, the flow in the bulk melt is generally unsteady and
even turbulent. Thus, the outlined flow-solidification/melting interplay happens frequently at
numerous positions but in a stochastic manner.