Geologic structures are usually the result of the powerful tectonic forces that occur within the earth. These forces fold and break rocks, form deep faults, and build mountains. Repeated applications of force—the folding of already folded rocks or the faulting and offsetting of already faulted rocks—can create a very complex geologic picture that is difficult to interpret. Most of these forces are related to plate tectonic activity. Some of the natural resources we depend on, such as metallic ores and petroleum, often form along or near geologic structures. Thus, understanding the origin of these structures is critical to discovering more reserves of our nonrenewable resources.
Structural geology is the study of the processes that result in the formation of geologic structures and how these structures affect rocks. Structural geology deals with a variety of structural features that can range in size from microscopic (such as traces of earlier folds after multiple events of deformation have occurred) to large enough to span the globe (such as midoceanic ridges).