Understanding the unusual dynamics of disordered systems trapped far from equilibrium remains a major challenge in soft condensed matter physics. Yet, these dynamics are not hard to observe. Take, for example, a thin plastic sheet and crumple it into a ball. It might not be immediately evident, but this seemingly mundane object exhibits many of the hallmark behaviors shared by complex non-equilibrium and disordered systems. These include ever-slowing relaxations, physical aging effects, intermittent mechanical responses, crackling noise, avalanche dynamics, and various memory effects.

Combining experiments on crumpled sheets and simulations of a disordered network of interacting elastic instabilities, we reveal the structural mechanism underlying and relating these behaviours in disordered mechanical systems. The emerging picture is of a disordered system of frustrated instabilities that self-organizes into a marginally stable state, where dynamics is governed by anomalously slow, noise-driven avalanches —a mechanism we argue may be broadly applicable to nonequilibrium disordered matter.

Applying our framework to data of seismic aftershocks following major earthquakes reveals strikingly similar temporal dynamics, suggesting that a similar physical mechanism underlies aftershock dynamics and the celebrated phenomenology of Omori's law.