Geology is a skill that is applicable across the minerals, petroleum, groundwater, engineering and environmental industries, as well as within social realms such as hazard management.
My recent experience has been in gold exploration. I have found that gold exploration is an art practiced largely by people with expertise in ore textures, metallogeny and igneous geology. Much of the art is underpinned by geochemistry. These are all aspects of geology that I find challenging, though enjoyable. However, I am essentially a structural geologist and orebodies are fundamentally three dimensional bodies formed by depostion of minerals from a fluid. Fluid pathways are usually formed by fracturing of the earth's crust, either by faulting in a regional stress field, or by local stress perturbations caused by intrusive bodies. Either way, structural geology is a critical part of understanding the distribution of ore within the host rock. The Pyramid Project in Queensland illustrates the importance of structural geology to even apparently simple ore occurrences.
Engineering geology is a critical field that operates at the interface between engineers, who build upon or excavate into a natural substrate, and geologists, who study the physical properties of the substrate. Engineers need to understand the engineering properties of the materials with which they are working. For a rock mass, these properties include mineralogy (carbonates to komatiites), weathering and alteration characteristics, the strength, orientation and continuity of planes of weakness and how they relate to local free faces, the nature of fracture fills (clays v. sands) and the characteristics of fluid flow in the rock mass. In faulted rock masses, these properties may be continuously varying, but each factor contributes to changes in the elastic constants and thus the shear wave velocity of a substrate.
Read about Multi-channel analysis of surface waves (MASW) for geotech characterisation of fault zones
For a soil mass, the strength depends on the structure of the soil, its age (younger soils are typically less well consolidated and more prone to liquefaction), its grainsize variability (engineers prefer poorly sorted materials, which they refer to as well-graded), and its pore water content. Then of course, somebody has to decide whether a unit is a soil or rock mass. Weak, poorly lithified rock masses that can be dug out with your fingers may be a geological rock but an engineering soil. Another factor that can have a major impact on the strength and liquefaction resistance of soil masses is historic landscape modification, typically by cut and fill. This has been widespread on the West Coast of New Zealand, particularly around Greymouth.