An introduction to geological mapping of our world and others

Map-making is a fundamental tool for developing geological knowledge. It involves data collection and interpretation and has its roots in the earliest discoveries in Earth Sciences. It is the starting point for stratigraphic and structural interpretations, metamorphic facies, geochronology and modelling studies - and underpins civil engineering. From the beginning, geological mapping rapidly evolved into far more than being a simple spatial catalogue of observable rock types and landforms on the Earth's land-surface; deductive reasoning allowing this knowledge to infer subsurface Earth structure. The same approaches are down-scaled to deduce processes on the grain-scale; or up-scaled to look out to extra-terrestrial objects. This is an introduction to fourteen papers in this Special Publication that celebrates geological mapping, its historical importance and future directions, and its use in applied geology together with developing knowledge of Earth and planetary evolution and processes. Geological mapping has a long tradition of adopting evolving technologies. This introduction considers the challenges faced in synthesising interpretations, sharing competing interpretations on maps and the role of open-access digital resources in facing these challenges.