What is geology?

As a discipline, geology is classically defined as the study of the Earth. Over the years, however, the geosciences have evolved to encompass a broad range of subdisciplines, each focusing on a specific group of Earth processes. Among these are the following:

Mineralogy - formation, chemical and physical properties, and classification of minerals

Petrology - formation, properties, and classification of rocks

Sedimentology - genesis, transport, and deposition of sediment, and the formation of sedimentary rocks

Structural geology - deformation of earth materials and resulting geologic structures

Tectonics - regional to global-scale deformation and structures resulting from interactions among pieces of the Earth's rigid outer layer, or lithosphere

Geomorphology - processes of landform evolution and landscape development

Hydrogeology - interrelationships of water and geologic materials and processes

In practice, geologists also draw heavily on the allied sciences of chemistry, physics, mathematics, and biology. Thus, geology is an interdisciplinary science, and in some cases to such a degree that there exist, for example, the subdisciplines of geochemistry, biogeochemistry, and geophysics.

The science of geology is also somewhat unique in that it deals with processes that occur over timescales that span seconds to billions of years and spatial scales ranging from the atomic to the planetary.

Earth image from Nasa Earth from Space collection taken by the Apollo 17 crew on December 7, 1972.