  Experiments reveal that structural transitions in thin sheets are mediated by
the passage of transient and stable mobile localized elastic excitations. These
``crumples'' or ``d-cones'' nucleate, propagate, interact, annihilate, and
escape. Much of the dynamics occurs on millisecond time scales. Nucleation
sites correspond to regions where generators of the ideal unstretched surface
converge. Additional stable intermediate states illustrate two forms of
quasistatic inter-crumple interaction through ridges or valleys. These
interactions create pairs from which extended patterns may be constructed in
larger specimens. The onset of localized transient deformation with increasing
sheet size is correlated with a characteristic stable crumple size, whose
measured scaling with thickness is consistent with prior theory and experiment
for localized elastic features in thin sheets. We offer a new theoretical
justification of this scaling.
