The map sheets of the Geological Atlas of Switzerland give detailed information about the uppermost layers of sediment and bedrock. Geological formations are represented by colours, conventional signs and symbols, according to their age, composition and tectonic structure. The topographic base used in the preparation of this series is the Swiss National Map at 1:25 000 scale. For each sheet published, there is also an explanatory booklet in which the geological formations and special features depicted on that sheet are described. These maps are an indispensable tool for geologists, engineers, planners, government departments, scientists and schools.