By River, Ocean, or Wind, Rocks Round the Same Way

Combining mathematical models with laboratory experiments and field measurements from a river, an ocean, and a dune field, a team led by geophysicist Douglas J. Jerolmack has found that the same general processes guide the rounding of those diverse particle types. They reported their findings in the journal Science Advances.

“We show that wind-blown sand, river pebbles, and wave-worked pebbles all round in the same way by colliding,” Jerolmack says. “And, more important, we show how nature selects for the conditions that lead to this universal behavior.”

The mathematical models explaining the universality of this evolution have been created in recent decades, in the effort to prove the Poincaré conjecture, a major breakthrough in pure mathematics. It turns out that the very same equations have a second, no less interesting interpretation as models for natural shape evolution.

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