Title: From Icy Soil Drips to Rivers of Brazil Nuts: Connections between Earths landscapes and everyday materials

Author (Invited): Rachel Glade, University of Rochester

Abstract:

The ice cream in your freezer, a sandcastle, human skin, dirt, toothpaste, a jar of nuts: these materials lie at the heart of soft matter physics, colloquially known as the study of all things squishy. Made up of macroscopic units such as colloids or sand grains, soft matter has an enhanced ability to deform and is inherently disordered, exhibiting nonlinear dynamics and emergent phenomena. Earth and planetary surfaces are home to some of the most complex soft materials in existence; for example, typical soil or river sediment is composed of a heterogeneous mixture of sticky sediment grains with different shape and size, fluids, and organic matter. Sediment dynamics result in striking landscape patterns that exist at time and length scales well beyond those typically studied in materials science. Here we explore connections between patterns on Earths surface and everyday materials. First we use numerical models to explore the role of grain shape in granular segregation processes that occur in rivers, landslides and other geophysical flows. Next we use remote sensing and a theoretical scaling analysis to show that large, slow-moving soil patterns in Arctic regions and on Mars may be analogous to surface-tension dominated fluid instabilities, with implications for our understanding of pattern development and dynamics in creeping, cohesive granular media. We hope to show that drawing connections between sediment dynamics and materials science can inform not only our understanding of planetary surfaces, but also materials in general.