Geologists may concentrate their studies or research in one or more of the following disciplines:
Economic geology: the study of ore genesis, and the mechanisms of ore creation, geostatistics.

Engineering geology: application of the geologic sciences to engineering practice for the purpose of assuring that the geologic factors affecting the location, design, construction, operation and maintenance of engineering works are recognized and adequately provided for;
Geophysics: the applied branch deals with the application of physical methods such as gravity, seismicity, electricity, magnetic properties to study the earth.

Geochemistry: the applied branch deals with the study of the chemical makeup and behaviour of rocks, and the study of the behaviour of their minerals.

Geochronology: the study of isotope geology specifically toward determining the date within the past of rock formation, metamorphism, mineralization and geological events (notably, meteorite impacts).

Geomorphology: the study of landforms and the processes that create them
Hydrogeology: the study of the origin, occurrence and movement of groundwater water in a subsurface geological system.

Igneous petrology: the study of igneous processes such as igneous differentiation, fractional crystallization, intrusive and volcanological phenomena.

Isotope geology: the case of the isotopic composition of rocks to determine the processes of rock and planetary formation.

Metamorphic petrology: the study of the effects of metamorphism on minerals and rocks.

Marine geology: the study of the seafloor; involves geophysical, geochemical, sedimentological and paleontological investigations of the ocean floor and coastal margins.
Marine geology has strong ties to physical oceanography and plate tectonics.

Palaeoclimatology: the application of geological science to determine the climatic conditions present in the Earth's atmosphere within the Earth's history.

Palaeontology: the classification and taxonomy of fossils within the geological record and the construction of a palaeontological history of the Earth.

Pedology: the study of soil, soil formation, and regolith formation.

Petroleum geology: the study of sedimentary basins applied to the search for hydrocarbons (oil exploration).

Planetary geology: the study of geology as it relates to other celestial bodies, namely planets and their moons.
This includes the subdiscipline of lunar geology, selenology, and martian geology, areology.

Sedimentology: the study of sedimentary rocks, strata, formations, eustasy and the processes of modern-day sedimentary and erosive systems.

Seismology: The study of earthquakes.

Structural geology: the study of folds, faults, foliation and rock microstructure to determine the deformational history of rocks and regions.

Volcanology: the study of volcanoes, their eruptions, lavas, magma processes and hazards.
Geologists may concentrate their studies or research in one or more of the following disciplines:
Economic geology: the study of ore genesis, and the mechanisms of ore creation, geostatistics.
Engineering geology: application of the geologic sciences to engineering practice for the purpose of assuring that the geologic factors affecting the location, design, construction, operation and maintenance of engineering works are recognized and adequately provided for;
Geophysics: the applied branch deals with the application of physical methods such as gravity, seismicity, electricity, magnetic properties to study the earth.
Geochemistry: the applied branch deals with the study of the chemical makeup and behaviour of rocks, and the study of the behaviour of their minerals.
Geochronology: the study of isotope geology specifically toward determining the date within the past of rock formation, metamorphism, mineralization and geological events (notably, meteorite impacts).
Geomorphology: the study of landforms and the processes that create them
Hydrogeology: the study of the origin, occurrence and movement of groundwater water in a subsurface geological system.
Igneous petrology: the study of igneous processes such as igneous differentiation, fractional crystallization, intrusive and volcanological phenomena.
Isotope geology: the case of the isotopic composition of rocks to determine the processes of rock and planetary formation.
Metamorphic petrology: the study of the effects of metamorphism on minerals and rocks.
Marine geology: the study of the seafloor; involves geophysical, geochemical, sedimentological and paleontological investigations of the ocean floor and coastal margins. Marine geology has strong ties to physical oceanography and plate tectonics.
Palaeoclimatology: the application of geological science to determine the climatic conditions present in the Earth's atmosphere within the Earth's history.
Palaeontology: the classification and taxonomy of fossils within the geological record and the construction of a palaeontological history of the Earth.
Pedology: the study of soil, soil formation, and regolith formation.
Petroleum geology: the study of sedimentary basins applied to the search for hydrocarbons (oil exploration).
Planetary geology: the study of geology as it relates to other celestial bodies, namely planets and their moons. This includes the subdiscipline of lunar geology, selenology, and martian geology, areology.
Sedimentology: the study of sedimentary rocks, strata, formations, eustasy and the processes of modern-day sedimentary and erosive systems.
Seismology: The study of earthquakes.
Structural geology: the study of folds, faults, foliation and rock microstructure to determine the deformational history of rocks and regions.
Volcanology: the study of volcanoes, their eruptions, lavas, magma processes and hazards.
Geologist