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Updated: Jan 8, 2026

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Génesis de "sandballs" por gotas de lluvia

Bertil Trottet^1,2, Daisuke Noto¹, Douglas J Jerolmack^1,3

¹Department of Earth and Environmental Science, University of Pennsylvania, Philadelphia, PA 19104.

Proceedings of the National Academy of Sciences of the United States of America

|December 22, 2025

Abstract:

In the water cycle, erosion begins with the entrainment of soil by raindrops. The discrete, discontinuous, and three-phase nature of raindrop erosion-at the boundary of fluid and granular mechanics-makes this problem particularly challenging, compared to better-studied sediment transport by river and wind currents. Past research has emphasized particle entrainment by raindrop splash at impact. Here, we report lab and field observations, that uncover a surprisingly rich and efficient postimpact phase. Raindrops impacting a dry, sloping, granular bed spontaneously form "sandballs;" drops of dense suspensions that can grow in mass to a jammed state by sediment entrainment, as they roll downhill like snowballs and magnify soil erosion. Careful control of drop conditions reveals two stable sandball morphologies: peanut-like shapes linked to hydrodynamic instabilities and toroidal forms that undergo mechanical locking from extreme sediment loading, which have potential implications for related problems in bioengineering, pharmaceuticals, and snow physics.

Palabras clave:

gotas laderas granulares granulación erosión del paisaje materia blanda de tierra

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