Geology is a vast field of science that encompasses the physical, historical, and environmental areas of study. These three areas of the study are the principal subdivisions of geology, which somehow overlap, but they also differ in significant ways overall. Therefore, we divide geology into three fundamental branches; i.e Physical Geology, Historical Geology, and Environmental Geology. Read: Introduction to Geology
1. Physical Geology
The study of the solid earth and the processes, which put an impact and bring changes to the physical landscape of the earth, like erosion, volcanic activities, convection of mantle, and earthquakes, etc, is known as Physical Geology. Physical geology can further be divided into many branches, which differ from one another in many ways, but are still interrelated and thus included in physical geology overall. These branches are:
- Petrology: This branch of physical geology includes the study of the origin, structure, history, and mineral composition of the rocks.
- Mineralogy: Rocks are mainly composed of minerals. The very basic object to study rocks is to obtain information about their mineral composition, structure, and crystal form of the minerals. Thus when we study the rock’s minerals, it is known as Mineralogy.
- Sedimentary Geology: Sedimentary geology is the study of sedimentation and sedimentary rock formation. Sediments are small pieces of bedrock, which are weathered and eroded from their parent rocks and then accumulate in low-lying areas, and then, by means of different chemical and physical processes, form sedimentary rocks.
- Geo-chemistry: Geo-chemistry deals with the identification of the substances of which the earth is composed; the investigation of their properties and the ways in which they interact, combine, and change; and the use of these processes to form new substances.
- Stratigraphy: Strata is the layers of rocks. When we study the history, order, and composition of rocks at levels of different strata, is known as Stratigraphy.
- Structural Geology: Structural geology is the study of the three-dimensional distribution of rock units with respect to their deformational histories.
- Geophysics: The physical activities of the earth, like earthquakes, volcanism, convection of mantle, erosion/denudation, etc are studied in this area of study.
2. Historical Geology:
Historical geology is the study of analyzing the earth’s past by investigating the processes and formation of rocks. The difference between physical and Historical Geology is that physical geology investigates the present position of the earth, while the past position of the planet is studied under Historical Geology. Historical geology can further be divided into the following sub-disciplines.
- Chronology: The study of the layers of rocks, as it relates to geologic time.
- Archaeology: Archaeology is the study of human history and prehistory through the excavation of sites and the analysis of artifacts and other physical remains.
- Paleontology: The study of how organisms evolve and their interactions in their environment by studying fossil records often found in rocks.
- Micropaleontology: The study of characteristics of micro-fossils.
- Geomorphology: How landforms, physical features, and geological structures on Earth were created and evolved.
- Geochronology: How old rocks and geological events are dated using signatures inherent in rocks.
3. Environmental Geology:
The interactions between humans and their geologic environments like rocks/soil (lithosphere), water(hydrosphere), air (atmosphere), and life (biosphere). Humans are impacted by Earth’s processes, and their activities have an impact on Earth. The influence of human activities on earth and earth processes on human life is known as Environmental Geology. Environmental geologists apply geological principles to solving environmental problems of water and land on which people, animals, and plants live, which may have resulted from human activities or natural processes. Environmental geology can be subdivided into the following branches:
- Ecology: Ecology means the relationship of living organisms with their environment. Geologically speaking, the interaction between living organisms and their geologic environment.
- Soil Sciences: Soil science is an important field of environmental sciences, that deals with the study of soil as a natural resource on the surface of the Earth including soil formation, classification, and mapping; physical, chemical, biological, and fertility properties of soils; and these properties in relation to the use and management of soils.
- Environmental geochemistry: Environmental geochemistry is concerned with the sources, distribution, and interactions of chemical elements in the rocks, soil, water, air, plant, animals, and human systems. The primary source of elements is igneous rocks of which silicates and aluminosilicates are the dominant compounds.
- Geomodelling: Geologic modeling, geological modeling, or geomodelling is the applied science of creating computerized representations of portions of the Earth’s crust based on geophysical and geological observations made on and below the Earth’s surface.
- Petrology: Understanding the rock processes and permeability.
- Climatology: The study of climates, climate change and impact of climate on human life, and the impact of human activities on climate. For example, global warming is the result of many human activities, and similarly, human migration is the outcome of climate effects.
4. Other Branches of Geology:
Apart from the above-classified branches of geology, there are several other branches, which we study in specific circumstances which, somehow are interconnected with one another.
- Economic Geology: Economic geology deals with the economic importance of minerals, ores, fossil fuels, and rock material.
- Mining Geology: The application of geological studies to mining engineering is called Mining Geology.
- Engineering Geology: It deals with the study of the application of geology to civil engineering. Because before building a bridge we need to study the geological features of that particular region. Constructing road geological surveys is a prerequisite.
- Geochemistry: Geochemistry is the science that uses the tools and principles of chemistry to explain the mechanisms behind major geological systems such as the Earth’s crust and its oceans. Mainly chemical composition and chemical changes and the effect of chemical activities on Earth’s material is studied in this branch.
- Geophysics: Geophysics is a subject of natural science concerned with the physical processes and physical properties of the Earth and its surrounding space environment, and the use of quantitative methods for their analysis.
- Spectral Geology: It is the measurement and analysis of portions of the electromagnetic spectrum to identify spectrally distinct and physically significant features of different rock types and surface materials, their mineralogy, and their alteration signatures.
- Biogeology: In geology, we study the interaction between the biosphere (where life is present) and the lithosphere (rigid part of the earth). In biogeology, we study the dependence of life on the lithosphere and the impact of living organisms on the lithosphere.
- Geologic Modeling: Geologic modeling, geological modeling or geomodelling is the applied science of creating computerized representations of portions of the Earth’s crust based on geophysical and geological observations made on and below the Earth’s surface.
- Hydrogeology: The distribution and movement of groundwater in the soil and rocks of the Earth’s crust is studied under the discipline of geology called Hydrology.
- Marine Geology: Marine geology which is also called geological oceanography is the study of the history and structure of the ocean floor. It involves geophysical, geochemical, sedimentological, and paleontological investigations of the ocean floor and coastal zone. Marine geology has strong ties to geophysics and to physical oceanography.
- Volcanology: Study of volcanic eruption, lava, magma, and related geological, geophysical, and geochemical phenomena. The term volcanology is derived from the Latin word Vulcan. Vulcan was the ancient Roman god of fire.
- Petroleum Geology: Among the branches of geology Petroleum geology is a very important branch. Petroleum geology is the study of the origin, occurrence, movement, accumulation, and exploration of hydrocarbon fuels i.e crude oil, natural gas, and coal. It refers to the specific set of geological disciplines that are applied to the search for hydrocarbons.