Dunes as Physical Systems - Dune Worlds: How Windblown Sand Shapes Planetary Landscapes - page 242

processes involved, and models can reproduce—whether at
the ripple scale or at the dune scale—the morphologies seen in
nature. Dunes and ripples are examples of emergent systems,
wherein the relentless application of simple rules can lead to
complex forms, and much of the work on such systems appears
in the physics rather than geography/geology literature. Inter-
estingly, a major motif in modern physics has been the appli-
cation of cellular-type models to understand such diverse

phenomena (Bak 1999) as earthquakes, wildfires and
stock-market crashes, wherein events can occur at a wide range
of scales, usually with a power-law size distribution. While
dunes themselves do not have such distributions, being rather
regular, the avalanches down their slip faces do. An engaging
discussion of self-organized systems which sets aeolian land-
forms in context is the topic by Ball (1999).