Before geomaterials become “hard” rocks, they commonly pass through stages in which they behave as soft-matter systems, such as complex fluids, gels, colloids, liquid crystals, and foams. During these stages, they can be regarded as geological soft matter, which commonly occurs during lithification, crystallization and deformation. The initiation of such soft-matter behaviour is highly sensitive to the surrounding physicochemical environment, leading to the formation of striking patterns and complex structures. Understanding how these structures form and evolve remains a major challenge in the Earth sciences. Examples include soft-sediment deformation structures such as load casts and flame structures; mineral dendrites; concretions and chemical banding; crack patterns such as septaria, mud cracks and lava polygons; and dissolution–precipitation forms such as travertine dams, scallops and stalactites. Other examples include patterns associated with microbial mats, such as stromatolitic structures, together with botryoidal and spherulitic textures, as well as hydro-geomorphological patterns such as channel networks and dunes, and vegetation patterns.

The physics underlying these patterns, which evolve progressively during the soft-matter stage, commonly involves complex non-equilibrium processes governed by self-organization and self-assembly. These processes allow complex spatiotemporal patterns to emerge from simple rules, while making the underlying physicochemical mechanisms difficult to infer from the pattern alone. Exploring such physical laws and establishing a geological soft-matter paradigm would not only provide an excellent opportunity to study pattern formation itself, but also help develop analogues for understanding geological processes in Earth’s history and potentially on other planets.

In this session, we discuss the potential application of the soft-matter paradigm to geological evolution research. We invite contributions that aim to deepen our understanding of complex patterns across scales in natural and experimental systems, investigating the physicochemical processes that generate them, through field observations, experimental work, theoretical modelling, and computational simulations. Contributions involving advanced quantification, conceptual advances, quantitative model development and modelling are warmly welcome.