ABSTRACT
Geological maps record a distribution of features on the ground as if they had been observed from above. References may be given to an explanatory report or memoir in which geological details noted in the field, such as thickness, anisotropy, and grading of materials, may be recorded. Maps which show the distribution of the various rocks and soils that occur close to the surface of the ground, are most useful for civil engineering work and may be available in ‘Solid’ and ‘Drift’ editions. The Drift edition is strictly a map of surface geology because it shows the position, and the general character, of all geological materials that occur at ground level. Maps of subsurface geology are needed by mining engineers and others whose engineering work is located at depth. The thickness and underground distribution of rock and soil are shown on maps of subsurface geology.
