Petrology (from Ancient Greek πέτρος (pétros) ‘rock’, and λόγος (lógos) ‘account, explanation, narrative’) or rock science, is a geological discipline, which through the use of investigations of various kinds (especially mineralogical, crystallographic, geochemical and chemical-isotopic), deals essentially with problems (physical, chemical and biological) inherent in the genesis and parentage of rocks.

The petrological investigation is carried out both with the observation and direct analysis of samples, and experimentally, recreating in laboratory the presumed genetic conditions of the rocks, both as chemical composition or mineralogical departure, and as parameters of pressure and temperature observing the compositional evolution of the mixture of departure during the subsequent phases of crystallization of minerals.

The study of rocks is very important for several reasons in particular:

  • Through this study, it is possible to know which minerals and chemical elements are composed of rocks, and from this data, information is obtained about the composition of the Earth’s crust and mantle.
  • The ages of the Earth can be calculated through various radiometric dating methods. From there, a chronological sequence of geologic events can be established.
  • The characteristics of the Earth are usually the same as the characteristics of a specific tectonic environment. With this information, scientists can reconstruct these tectonic processes.
  • Studying the rock layers below the Earth’s surface helps to better understand the Earth’s history.
  • Many rocks contain minerals that are very important. These provide humans with valuable raw materials on which their livelihoods and technological development depend.

Petrology branches

Petrological studies cover the three major extant rock types: igneous, sedimentary, and metamorphic. Other subdisciplines are included in petrology, such as petrography. The latter is basically based on the principles and methods used by mineralogy. This is because most rocks are composed of minerals and originated under similar conditions. Its importance lies in the fact that the minerals contained in rocks and their chemical structure provide valuable information about the composition of the earth. In addition, many rocks harbor important minerals; from these we obtain very important raw materials for life and technological development.

Igneous petrology

Focuses on the study of the composition and structure of igneous rocks, which are basically volcanic and plutonic rocks. This type of rock, such as granite or basalt, is formed when rock or magma crystallizes.

Sedimentary petrology

This branch focuses on studying the composition and structure of sedimentary rocks. These types of rocks are sandstones, shales, or limestones, which are pieces or particles of rock that originated from other rocks.

Sedimentary rocks are also formed from biological or chemical deposits and are almost always joined by a finer material.

Metamorphic petrology

As the name implies, it is geared toward studying the composition and texture of metamorphic rocks. These are the slate, marble, gneiss or schist, though sedimentary or igneous rocks are possibly undergone chemical, mineralogical and structural changes as a result of extreme degrees of temperature, pressure or both.

Experimental petrology

In this area of petrology, high-pressure, high-temperature equipment is used to study the geochemistry of rocks. Similarly, the phase relationships of materials, natural or synthetic, subjected to very high temperatures and pressures are studied.

This type of experiment is particularly useful because it is used to investigate rocks found in the lower crust and upper mantle. These rocks rarely survive the journey to the surface in their natural or primitive conditions.

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