A batholith () is a large mass of intrusive

igneous rock Igneous rock ( ), or magmatic rock, is one of the three main rock types, the others being sedimentary and metamorphic. Igneous rocks are formed through the cooling and solidification of magma or lava. The magma can be derived from partial ...

(also called plutonic rock), larger than in area, that forms from cooled

magma Magma () is the molten or semi-molten natural material from which all igneous rocks are formed. Magma (sometimes colloquially but incorrectly referred to as ''lava'') is found beneath the surface of the Earth, and evidence of magmatism has also ...

deep in the

Earth's crust Earth's crust is its thick outer shell of rock, referring to less than one percent of the planet's radius and volume. It is the top component of the lithosphere, a solidified division of Earth's layers that includes the crust and the upper ...

. Batholiths are almost always made mostly of

felsic In geology, felsic is a grammatical modifier, modifier describing igneous rocks that are relatively rich in elements that form feldspar and quartz.Marshak, Stephen, 2009, ''Essentials of Geology,'' W. W. Norton & Company, 3rd ed. It is contrasted ...

or intermediate rock types, such as

granite Granite ( ) is a coarse-grained (phanerite, phaneritic) intrusive rock, intrusive igneous rock composed mostly of quartz, alkali feldspar, and plagioclase. It forms from magma with a high content of silica and alkali metal oxides that slowly coo ...

, quartz monzonite, or

diorite Diorite ( ) is an intrusive rock, intrusive igneous rock formed by the slow cooling underground of magma (molten rock) that has a moderate content of silica and a relatively low content of alkali metals. It is Intermediate composition, inter ...

(see also '' granite dome''). Intrusion types

Formation

Although they may appear uniform, batholiths are in fact structures with complex histories and compositions. They are composed of multiple masses, or '' plutons'', bodies of igneous rock of irregular dimensions (typically at least several kilometers) that can be distinguished from adjacent igneous rock by some combination of criteria including age, composition, texture, or mappable structures. Individual plutons are solidified from magma that traveled toward the surface from a zone of partial melting near the base of the Earth's crust. Vitosha platoto

Traditionally, these plutons have been considered to form by ascent of relatively buoyant magma in large masses called ''plutonic diapirs''. Because the diapirs are liquified and very hot, they tend to rise through the surrounding native

country rock Country rock is a music genre that fuses rock and country. It was developed by rock musicians who began to record country-flavored records in the late 1960s and early 1970s. These musicians recorded rock records using country themes, vocal sty ...

, pushing it aside and partially melting it. Most diapirs do not reach the surface to form

volcano A volcano is commonly defined as a vent or fissure in the crust of a planetary-mass object, such as Earth, that allows hot lava, volcanic ash, and gases to escape from a magma chamber below the surface. On Earth, volcanoes are most oft ...

es, but instead they slow down, cool, and usually solidify 5 to 30 kilometers underground as plutons (hence the use of the word ''pluton''; in reference to the Roman god of the underworld

Pluto Pluto (minor-planet designation: 134340 Pluto) is a dwarf planet in the Kuiper belt, a ring of Trans-Neptunian object, bodies beyond the orbit of Neptune. It is the ninth-largest and tenth-most-massive known object to directly orbit the Su ...

). An alternate view is that plutons are formed by aggregation of smaller volumes of magma that ascend as dikes. A batholith is formed when many plutons converge to form a huge expanse of granitic rock. Some batholiths are mammoth, paralleling past and present

subduction Subduction is a geological process in which the oceanic lithosphere and some continental lithosphere is recycled into the Earth's mantle at the convergent boundaries between tectonic plates. Where one tectonic plate converges with a second p ...

zones and other heat sources for hundreds of kilometers in

continental crust Continental crust is the layer of igneous, metamorphic, and sedimentary rocks that forms the geological continents and the areas of shallow seabed close to their shores, known as '' continental shelves''. This layer is sometimes called '' si ...

. One such batholith is the

Sierra Nevada Batholith The Sierra Nevada Batholith is a large batholith that is approximately 400 miles long and 60-80 miles wide which forms the core of the Sierra Nevada mountain range in California, exposed at the surface as granite. The batholith is composed of ...

, which is a continuous granitic formation that makes up much of the

Sierra Nevada The Sierra Nevada ( ) is a mountain range in the Western United States, between the Central Valley of California and the Great Basin. The vast majority of the range lies in the state of California, although the Carson Range spur lies primari ...

in California. An even larger batholith, the Coast Plutonic Complex, is found predominantly in the

Coast Mountains The Coast Mountains () are a major mountain range in the Pacific Coast Ranges of western North America, extending from southwestern Yukon through the Alaska Panhandle and virtually all of the British Columbia Coast, Coast of British Columbia sout ...

of western Canada; it extends for 1,800 kilometers and reaches into southeastern Alaska.

Surface expression and erosion

A batholith is an exposed area of (mostly) continuous plutonic rock that covers an area larger than 100 square kilometers (40 square miles). Areas smaller than 100 square kilometers are called ''

stocks Stocks are feet and hand restraining devices that were used as a form of corporal punishment and public humiliation. The use of stocks is seen as early as Ancient Greece, where they are described as being in use in Solon's law code. The law de ...

''. However, the majority of batholiths visible at the surface (via outcroppings) have areas far greater than 100 square kilometers. These areas are exposed to the surface through the process of

erosion Erosion is the action of surface processes (such as Surface runoff, water flow or wind) that removes soil, Rock (geology), rock, or dissolved material from one location on the Earth's crust#Crust, Earth's crust and then sediment transport, tran ...

accelerated by continental uplift acting over many tens of millions to hundreds of millions of years. This process has removed several tens of square kilometers of overlying rock in many areas, exposing the once deeply buried batholiths. Batholiths exposed at the surface are subjected to huge pressure differences between their former location deep in the earth and their new location at or near the surface. As a result, their

crystal structure In crystallography, crystal structure is a description of ordered arrangement of atoms, ions, or molecules in a crystalline material. Ordered structures occur from intrinsic nature of constituent particles to form symmetric patterns that repeat ...

expands slightly over time. This manifests itself by a form of

mass wasting Mass wasting, also known as mass movement, is a general term for the movement of rock (geology), rock or soil down slopes under the force of gravity. It differs from other processes of erosion in that the debris transported by mass wasting is no ...

called exfoliation. This form of weathering causes convex and relatively thin sheets of rock to slough off the exposed surfaces of batholiths (a process accelerated by frost wedging). The result is fairly clean and rounded rock faces. A well-known result of this process is Half Dome in

Yosemite Valley Yosemite Valley ( ; ''Yosemite'', Miwok for "killer") is a U-shaped valley, glacial valley in Yosemite National Park in the western Sierra Nevada (U.S.), Sierra Nevada mountains of Central California, United States. The valley is about long a ...

Examples

Africa

*Aswan Granite Batholith *Cape Coast Batholith, Ghana *Heerenveen Batholith, South Africa *Paarl Rock, South Africa *Darling Batholith, South Africa * Hook granite massif, Zambia *Mubende Batholith, Uganda

Antarctica

*Antarctic Peninsula Batholith *Queen Maud Batholith

Asia

* Angara-Vitim batholith, Siberia * Bhongir Fort Batholith,

Telangana Telangana is a States and union territories of India, state in India situated in the Southern India, south-central part of the Indian subcontinent on the high Deccan Plateau. It is the List of states and union territories of India by area, ele ...

, India * Chibagalakh batholith, Siberia *Mount Abu, India * Gangdese batholith, Himalaya *Trans-Himalayan Batholith, Himalaya * Kalba-Narym batholith, Kazakhstan *Karakorum Batholith, Himalaya *Tak batholith, Thailand *Tien Shan batholith, Central Asia *Ranchi batholith, India

Europe

* La Pedriza, Spain. *Bindal Batholith, Norway * Cornubian batholith, England *Corsica-Sardinia Batholith * Donegal batholith, Ireland *Leinster Batholith, Ireland *Mancellian batholith, France * North Pennine Batholith, England * Ljusdal Batholith, Sweden * Mt-Louis-Andorra Batholith *Riga Batholith, Latvia *Salmi Batholith, Republic of Karelia, Russia *Sunnhordaland Batholith, Norway * Transscandinavian Igneous Belt, Sweden and Norway :*Revsund Massif :*Rätan Batholith :*Småland–Värmland Belt *

Vitosha Vitosha ( ), the ancient ''Scomius'' or ''Scombrus'', is a mountain massif, on the outskirts of Sofia, the capital of Bulgaria. Vitosha is one of the symbols of Sofia and the closest site for hiking, alpinism and skiing. Convenient bus lines and ...

(mountain massif) and Plana (mountain),

Sofia Sofia is the Capital city, capital and List of cities and towns in Bulgaria, largest city of Bulgaria. It is situated in the Sofia Valley at the foot of the Vitosha mountain, in the western part of the country. The city is built west of the Is ...

, Bulgaria

North America

* Bald Rock Batholith * Enchanted Rock, Texas * Boulder Batholith *

British Virgin Islands The British Virgin Islands (BVI), officially the Virgin Islands, are a British Overseas Territories, British Overseas Territory in the Caribbean, to the east of Puerto Rico and the United States Virgin Islands, US Virgin Islands and north-west ...

, Virgin Gorda * Chambers-Strathy Batholith * Chilliwack batholith *Golden Horn Batholith *

Idaho Batholith The Idaho Batholith is a granitic and granodioritic batholith of Cretaceous- Paleogene age that covers approximately of central Idaho and adjacent Montana. The batholith has two lobes that are separate from each other geographically and ge ...

*Ilimaussaq Batholith,

Greenland Greenland is an autonomous territory in the Danish Realm, Kingdom of Denmark. It is by far the largest geographically of three constituent parts of the kingdom; the other two are metropolitan Denmark and the Faroe Islands. Citizens of Greenlan ...

* Kenosha Batholith * Mount Stuart Batholith, Washington * Wallowa Batholith,

Oregon Oregon ( , ) is a U.S. state, state in the Pacific Northwest region of the United States. It is a part of the Western U.S., with the Columbia River delineating much of Oregon's northern boundary with Washington (state), Washington, while t ...

* Peninsular Ranges, Baja and

Southern California Southern California (commonly shortened to SoCal) is a geographic and Cultural area, cultural List of regions of California, region that generally comprises the southern portion of the U.S. state of California. Its densely populated coastal reg ...

* Pike's Peak Granite Batholith * Ruby Mountains *Rio Verde Batholith, Mexico * San Lorenzo Batholith,

Puerto Rico ; abbreviated PR), officially the Commonwealth of Puerto Rico, is a Government of Puerto Rico, self-governing Caribbean Geography of Puerto Rico, archipelago and island organized as an Territories of the United States, unincorporated territo ...

* South Mountain Batholith, Nova Scotia * Town Mountain Granite batholith, Texas * Wyoming batholith

Oceania

*Cullen Batholith, Australia * Kosciuszko Batholith, Australia * Moruya Batholith, Australia * Scottsdale Batholith, Australia Stratigraphic revision and remapping of the Mathinna Supergroup between the River Tamar and the Scottsdale Batholith, northeast Tasmania
Department of Infrastructure, Energy and Resources. Mineral Resources Tasmania. June 2011 *Median Batholith, New Zealand *New England Batholith, Australia

South America

* Achala Batholith, Argentina * Antioquia Batholith, Colombia *Guanambi Batholith,

Bahia Bahia () is one of the 26 Federative units of Brazil, states of Brazil, located in the Northeast Region, Brazil, Northeast Region of the country. It is the fourth-largest Brazilian state by population (after São Paulo (state), São Paulo, Mina ...

, Brazil * Parguaza rapakivi granite Batholith, Venezuela and Colombia * Cerro Aspero Batholith, Argentina * Coastal Batholith of Peru * Colangüil Batholith, Argentina * Cordillera Blanca Batholith, Peru * Vicuña Mackenna Batholith, Chile * Elqui-Limarí Batholith, Chile and Argentina * Futrono-Riñihue Batholith, Chile * Illescas Batholith, Uruguay * Coastal Batholith of central Chile * Panguipulli Batholith, Chile *Patagonian Batholith, Chile and Argentina ** North Patagonian Batholith ** South Patagonian Batholith

References

* Plummer, McGeary, Carlson, ''Physical Geology'', Eighth Edition (McGraw-Hill: Boston, 1999) pages 61–63 * Glazner, Bartley, Coleman, Gray, Taylor
Are plutons assembled over millions of years by amalgamation from small magma chambers?
GSA Today: Vol. 14, No. 4, pp. 4–11

External links

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