Geology emerged as a science in the early 19th century by giving itself the objective of reconstituting the history of the Earth since its birth through those original archives constituted by rocks. The time scale of geology is long and as a science it leaves the field of historical time and that of theories of the Earth, grounding itself first in the geometrical disposition of the rock-layers, then in its focus on the genesis and meaning of rocks and fossils. The simultaneous invention of the geological map testifies both to the necessity of describing and locating rocks in space and time, and to that of expressing the results visually in order to reduce their complexity and facilitate their rapid and synthetic understanding, thus at the same time helping to develop the science of geology.