In geology an intrusion is usually a body of igneous rock that has crystallized from a molten magma below the surface of the Earth. Intrusive rocks include all varieties of igneous rocks from coarse-grained, phaneritic granites of large batholiths to very fine grained, aphanitic, rhyolites in volcanic necks or feeder pipes. In composition, intrusive rocks also include the entire sequence of igneous rock types from the dense and dark ultramafic peridotites to the very light-colored and low-density alkali granites and syenites. Bodies of magma that solidify underground before they reach the surface of the earth are called plutons, named for Pluto, the Roman god of the underworld. A well-known example of an igneous intrusion is Devil's Tower in Wyoming, USA. 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. ... 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. ... Quartz crystal A crystal is a solid in which the constituent atoms, molecules, or ions are packed in a regularly ordered, repeating pattern extending in all three spatial dimensions. ... This article is about the type of rock. ... Earth, also known as the Earth or Terra, is the third planet outward from the Sun. ... Granite is a common and widely-occurring group of intrusive felsic igneous rocks that form at great depths and pressures under continents. ... Half Dome A batholith is a large emplacement of igneous intrusive (also called plutonic) rock that forms from cooled magma deep in the Earths crust. ... Rhyolite Rhyolite is an igneous, volcanic (extrusive) rock, of felsic composition, with aphanitic to porphyritic texture. ... This article is about volcanoes in geology. ... Peridotite Peridotite is a dense, coarse grained ultrabasic rock, consisting mainly of the minerals olivine and pyroxene. ... Syenite Syenite is a coarse-grained intrusive igneous rock of the same general composition as granite but with the quartz either absent or present in relatively small amounts. ... Pluto was the god of the underworld in Roman mythology. ... Roman mythology can be considered as two parts. ... For other meanings of the word underworld see Underworld (disambiguation) In the study of mythology and religion, the underworld is a generic term approximately equivalent to the lay term afterlife, referring to any place to which newly-dead souls go. ... Devils Tower National Monument Devils Tower is a geological feature located in eastern Wyoming that was established as the first United States National Monument in 1906. ... State nickname: Equality State Other U.S. States Capital Cheyenne Largest city Cheyenne Governor Dave Freudenthal Official languages English Area 253,554 km² (10th)  - Land 251,706 km²  - Water 1,851 km² (0. ... The word Usa has more than one meaning: U.S.A. - The United States of America Usa, Oita - A city in Japan This is a disambiguation page — a navigational aid which lists other pages that might otherwise share the same title. ...

Intrusive rocks also exist in a wide range of forms from mountain range sized batholiths to thin vein-like fracture fillings of aplite. Structural types include: Aplite is a fine to very fine-grained sugary-textured rock of granite composition. ...

• batholith: large irregular intrusions.
• stock: smaller irregular disordant intrusions.
• dike: a relatively narrow tabular discordant body with near vertical attitude.
• sill: a relatively thin tabular concordant body intruded along bedding planes, horizontal attitude.
• pipe or volcanic neck: circular or tube shaped nearly vertical body which may have been a feeder vent for a volcano.
• laccolith: concorant body with essentially flat base and dome shaped upper surface, usually has a feeder pipe below.

Diapir is the more general term for intrusions that includes both igneous and non-igneous structures, such as salt domes. A diapir is any relatively mobile mass that intrudes into preexisting strata. Diapirs commonly intrude vertically through more dense rocks because of buoyancy forces associated with relatively low-density rock types, such as salt, shale and hot magma, all of which form diapirs. The process is known as diapirism. Half Dome A batholith is a large emplacement of igneous intrusive (also called plutonic) rock that forms from cooled magma deep in the Earths crust. ... A dike in geology refers to a tabular intrusive igneous body. ... In geology, a sill is a tabular, often horizontal mass of igneous rock that has been intruded laterally between older layers of sedimentary rock, beds of volcanic lava or tuff, or even along the direction of foliation in metamorphic rock. ... This article is about volcanoes in geology. ... A laccolith is any of a type of igneous intrusion (or concordant pluton) that has been injected between two strata of a sedimentary bed. ... A salt dome is formed when a thick bed of evaporite minerals (mainly salt, or halite) found at depth intrudes vertically into surrounding rock strata, forming a diapir. ... Density (symbol: ρ - Greek: rho) is a measure of mass per unit of volume. ... In physics, buoyancy is an upward force on an object immersed in a fluid (i. ...

Piercement structures may be created by movement through strata.

By pushing upward and piercing overlying rock layers, diapirs can form anticlines, salt domes and other structures capable of trapping petroleum and natural gas. Igneous intrusions themselves are typically too hot to allow the preservation of preexisting hydrocarbons. Nodding donkey pumping an oil well near Sarnia, Ontario, 2001 Petroleum (from Latin petrus – rock and oleum – oil), mineral oil, or crude oil, sometimes colloquially called black gold, is a thick, dark brown or greenish flammable liquid, which exists in the upper strata of some areas of the Earths... Natural gas rig Natural gas is a gas produced by the anaerobic decay of organic material. ... In chemistry, a hydrocarbon is a cleaning solution consisting only of carbon (C) and hydrogen (H). ...

A mud volcano may be created by a pressurized mud diapir which breaches the Earth's surface or ocean bottom.