We present Visual Sedimentation, a new design metaphor for visualizing streaming data inspired by the geological process of sedimentation. Our work started by early experiments visualiz- ing political Twitter streams during the French 2012 presidential elections, and social interactions during a TV show. In both cases, the positive feedback we received expressed an unexpectedly high level of engagement from users, guiding our generalization of the metaphor. This article explores Visual Sedimentation and describes a new generative design space for Information Visualization. Geological sedimentation is our inspiration as it smoothly aggregates falling objects by com- pacting them into strata. We use this idea to visualize changing in- formation in a new way by providing continuity between the repre- sentation of new and older data. The metaphor preserves an overall visual encoding while making it suitable for monitoring streaming data generated at unpredictable rates.