Geology is the science of construction, the composition and structure of the earth’s crust, its physical properties and development history, as well as the processes that they shaped and still form today. The term is also used for geological construction, for example The Geology of the Alps.

The term geology in the present sense is first found in 1778 by Jean-André Deluc (1727-1817). Horace-Bénédict de Saussure (1740-1799) introduced geology in 1779 as a fixed concept. Previously, the term geognosy was common.

Geologists are concerned with the earth’s crust, rocks as well as petroleum and gas (petrogeology). Both the spatial relationships between different rock bodies, as well as the composition and internal structure of the individual rocks, provide information on the deciphering of the conditions under which these were created. The geologist is responsible for the detection and development of raw materials such as metal ores, industrial minerals and building materials such as sands, gravel and clays, as well as silicon for the solar industry, without which further economic development would not be possible. In addition, it is also active in the protection of drinking water as well as in energy products such as petroleum or gas and coal. Finally, the geologists are responsible for the exploration of the site, especially in the case of larger construction projects, in order to avoid settlements, landslides and groundbreaks in the long term.

In the field or underground, the geologist divides the open (open) rocks into defined units by means of external features. These mapping units must be displayed at the selected scale on a geological map, or in a geological profile. By extrapolation, it can predict how the rocks are stored in the subsoil with great probability.

However, a more detailed investigation of the rocks (petrography, petrology) usually takes place in the laboratory.

Mineralogy is concerned with the individual, partly microscopic, constituents of the rocks, the minerals.
The paleontology is concerned with the fossil content of sedimentary rocks.
Such detailed studies on a small scale provide the data and facts for the large-scale investigations of general geology.

Geology has many different points of contact with other natural sciences, which are summarized as geosciences. Geochemistry, for example, considers chemical processes in the Earth system – and uses methods from chemistry to obtain additional information on geoscientific questions. The same applies to geophysics and geodesy. Even mathematics has produced a special branch, geostatistics, which is particularly used in mining. Since the 1970s, there has been a certain trend in the geosciences from more qualitative-describing studies to more quantitative methods. Despite the increased computing power of modern computers, these numerical methods still reach their limits because of the enormous variability and complexity of geoscientific parameters.

In the border area to astronomy, planetary geology or astrogeology moves as a sub-area of ​​planetology, which deals with the composition, the internal structure, and the forming processes on alien bodies of heaven. Geological questions and the application of geological methods outside the Earth have gained in importance, especially since the beginning of space exploration and our exploration of our solar system using probes and satellites.