University of Pennsylvania geophysicists Hugo Ulloa and Douglas Jerolmack, along with their colleagues, have identified a significant Earth-shaping process driven by snowball-like sediment clusters they term “sandballs.” This research, utilizing a custom-built sloped channel, offers fundamental insights into how rain affects landscapes, soil loss, and agriculture.
These sandballs form when raindrops strike dry, sloped soil, gathering and growing as they roll downhill, picking up grains of sand. They can manifest as either peanut-shaped clumps with liquid cores or stable, donut-shaped structures with airy centers, continuing to cause erosion long after the initial impact.
By precisely defining the physics of these soft, mixed materials, the team aims to enhance the scientific understanding of how raindrops interact with dry surfaces. Their findings are also expected to inform the development of engineered systems that use liquids to bind granular matter, applicable in areas from soil stabilization to various manufacturing processes.