In nature, erosion patterns are driven by the interactions of flow and topography. Here, researchers study that process in the lab by placing an inclined block of caramel in quiescent syrup and watching as it dissolves. Initially, the bottom surface of the block develops regularly-spaced plumes — the dark lines seen in the first image. But because the caramel-laden plumes are heavier than the surrounding fluid, the flow quickly becomes unstable. The plumes cross one another and begin to carve chevrons into the caramel.
The chevrons appear to march their way upward in the video. They slowly grow and change into a distinctly scalloped pattern. Scallops like these are often seen by geologists in caves and icebergs, and the authors argue that their results and modeling indicate the importance of buoyant flow effects on such natural formations. (Image and research credit: C. Cohen et al.)