  A condition is defined which determines if a supertranslation is induced in
the course of a general evolution from one isolated horizon phase to another
via a dynamical horizon. This condition fixes preferred slices on an isolated
horizon and is preserved along an Isolated Horizon. If it is not preserved, in
the course of a general evolution, then a supertranslation will be said to have
been induced. A simple example of spherically symmetric dynamical horizons is
studied to illustrate the conditions for inducing supertranslations.
