This paper is a thought experiment to attune to the geo-physical and geo-political materialities of sediment, a terra-aqueous substance produced when the earth's continental surfaces intra-act with the atmosphere and are chemically transformed by it. The paper is framed by questions of how to engage more closely with the dynamics of earth systems and of how social and political agency emerges alongside earth forces. Sediment is important to such questions because it is the mechanism by which the earth recycles itself and is thick with the climatological and geological histories that have conditioned the possibility of life on the planet. While acknowledging the import of Deleuze and Guattari's metaphysics to such questions, the paper takes a material approach to them. It is based on field work in Bangladesh, but also traverses a range of scientific, historical and theoretical literature. It is arranged in four sections that loosely correspond to the sedimentary cycle. It follows sediment from chemical processes on rock surfaces in the Himalayas, to its lively travels in monsoonal rivers across flood plains to its eventual deposition and subterranean diagenesis. In each section, the paper discusses the material processes at work, their socio-political enmeshments and the theoretical implications of these intra-actions. The paper concludes that sediment serves as a reminder not only of close entanglements of geo-physical and geo-political becomings, but also of the profound indifference of earth systems to human affairs, and asks what this might mean for the re-imagination of politics.