Petrology is a field of geology which focuses on the study of rocks and the conditions by which they form. There are three branches of petrology, corresponding to the three types of rocks: igneous, metamorphic, and sedimentary. The word petrology itself comes from the Greek "petros", or rock. Geology (from Greek γη- (ge-, the earth) and λογος (logos, word, reason)) is the science and study of the Earth, its composition, structure, physical properties, history, and the processes that shape it. ... Sedimentary, volcanic, plutonic, metamorphic rock types of North America. ... Igneous rocks are formed when molten rock (magma) cools and solidifies, with or without crystallization, either below the surface as intrusive (plutonic) rocks or on the surface as extrusive (volcanic) rocks. ... Metamorphic rock is the result of the transformation of a pre-existing rock type, the protolith, in a process called metamorphism, which means change in form, derived from the Greek words meta, change, and morphe, form. The protolith is subjected to extreme heat (>150 degrees Celsius) and pressure causing profound... Two types of sedimentary rock: limey shale overlaid by limestone. ...

• Igneous petrology focuses on the genesis of rocks that crystallized from a magma.
• Metamorphic petrology focuses on the changes that a rock undergoes as a result primarily of extreme pressure and temperature.
• Sedimentary petrology focuses on the processes by which sediments, or clastics, are cemented together to form sedimentary rocks.

Petrology utilizes the classical fields of mineralogy, microscopic petrography, and chemical analyses to describe the composition and texture of rocks. Modern petrologists also include the principles of geochemistry and geophysics through the studies of geochemical trends and cycles and the use of thermodynamic data and experiments to better understand the origins of rocks. This article is about the type of molten rock. ... Mineralogy is an earth science that involves the chemistry, crystal structure, and physical (including optical) properties of minerals. ... Petrography is the description of rocks and their textures. ... The field of geochemistry involves study of the chemical composition of the Earth and other planets, chemical processes and reactions that govern the composition of rocks and soils, and the cycles of matter and energy that transport the Earths chemical components in time and space. ... Geophysics, the study of the earth by quantitative physical methods, especially by seismic reflection and refraction, gravity, magnetic, electrical, electromagnetic, and radioactivity methods. ... Thermodynamics (Greek: thermos = heat and dynamic = change) is the physics of energy, heat, work, entropy and the spontaneity of processes. ...

See also Important publications in petrology Foundations Principles of Geology Author: Charles Lyell Publication data: 1830–1833. ...