Geologic maps are 2D images that show the location and extent of geologic features like rock units and faults and are made of the surface or subsurface. Many geologic features such as faults and boundaries demarking rocks of differing ages and types are 3D surfaces within the earth, and a surface geologic map displays the intersection of the earth’s topography with these subsurface surfaces. Surface geologic maps are most commonly displayed over a topographic base, often colorful, are of considerable value to society and are commonly used in a variety of endeavors such as geologic hazard and risk evaluations, water management, dam safety, resource and land management, resource exploitation, environmental evaluations, and education. Subsurface maps, with the surfaces commonly displayed as depth below sea-level, are arguably the most important geologic tool in active fault evaluations, carbon sequestration, some environmental evaluations, water management, natural gas storage field siting and operations, oil and exploration and field operations, and mining.
A geologic cross section displays a side view of the earth. The configurations shown in a cross section are interpretive and there can multiple interpretations in area of complex geology. The best constrained cross sections utilize data from wells (oil & gas, water) and geophysical techniques such as seismic reflection.
Integrating geologic mapping and cross sections produces a 3D volume that is much better constrained and less interpretive than standalone maps and cross sections. These 3D geologic volumes are much easier to produce with recent developments in geologic and geophysical mapping software and more powerful workstations.