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{{short description|Magnesium- and iron-rich extrusive igneous rock}}
{{Other uses}}
{{good article}}
{{pp-semi-indef}}
{{Use British English|date=December 2020}} <!--based on existing usage ("colour")-->
{{Use dmy dates|date=December 2020}} <!--No existing usage; for consistency with British English-->
{{Infobox rock
|name=Basalt
|type=Igneous
|image=Basalt 12 (48674276333).jpg
|image_caption=
|composition=[[Mafic]]: [[plagioclase]], [[amphibole]], and [[pyroxene]]
|composition_secondary=Sometimes [[feldspathoid]]s or [[olivine]]
}}

'''Basalt''' ({{IPAc-en|UK|ˈ|b|æ|s|ɒ|l|t|,_|-|ɔː|l|t|,_|-|əl|t}};<ref name=cambridge>{{Cite dictionary |url=https://dictionary.cambridge.org/dictionary/english/basalt |access-date=4 December 2024 |title=basalt |dictionary=Cambridge Dictionary |publisher=[[Cambridge University Press]]}}</ref><ref name=lexico>{{Cite dictionary |url=http://www.lexico.com/definition/basalt |archive-url=https://web.archive.org/web/20200203123653/https://www.lexico.com/definition/basalt |url-status=dead |archive-date=3 February 2020 |title=basalt |dictionary=[[Lexico]] UK English Dictionary |publisher=[[Oxford University Press]]}}</ref> {{IPAc-en|US|b|ə|ˈ|s|ɔː|l|t|,_|ˈ|b|eɪ|s|ɔː|l|t}})<ref name=MW>{{cite Merriam-Webster|basalt}}</ref> is an [[aphanite|aphanitic]] (fine-grained) [[extrusive]] [[igneous rock]] formed from the rapid cooling of low-[[viscosity]] [[lava]] rich in [[magnesium]] and [[iron]] ([[mafic]] lava) exposed at or very near the [[planetary surface|surface]] of a [[terrestrial planet|rocky planet]] or [[natural satellite|moon]]. More than 90% of all [[volcanic rock]] on Earth is basalt. Rapid-cooling, fine-grained basalt has the same chemical composition and mineralogy as slow-cooling, coarse-grained [[gabbro]]. The eruption of basalt lava is observed by geologists at about 20 volcanoes per year. Basalt is also an important rock type on other planetary bodies in the [[Solar System]]. For example, the bulk of the plains of [[volcanism on Venus|Venus]], which cover ~80% of the surface, are basaltic; the [[lunar mare|lunar maria]] are plains of flood-basaltic [[lava flow]]s; and basalt is a common rock on the surface of [[Mars]].

Molten basalt lava has a low viscosity due to its relatively low [[silica]] content (between 45% and 52%), resulting in rapidly moving lava flows that can spread over great areas before cooling and solidifying. [[Flood basalt]]s are thick sequences of many such flows that can cover hundreds of thousands of square kilometres and constitute the most voluminous of all volcanic formations.

Basaltic [[magma]]s within Earth are thought to originate from the [[upper mantle (Earth)|upper mantle]]. The chemistry of basalts thus provides clues to processes deep in [[structure of Earth|Earth's interior]].
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== Definition and characteristics ==
[[File:Basalt qapf.jpg|thumb|[[QAPF diagram]] with basalt/andesite field highlighted in yellow. Basalt is distinguished from andesite by SiO<sub>2</sub>&nbsp;<&nbsp;52%.]]
[[File:TAS-Diagramm-basalt.png|thumb|upright=1.35|Basalt is field B in the [[TAS classification]].]]
[[File:VesicularBasalt1.jpg|thumb|Vesicular basalt at [[Sunset Crater]], Arizona. [[US quarter]] (24mm) for scale.]]
[[File:Basalt columns in yellowstone 2.jpg|Columnar basalt flows in [[Yellowstone National Park]], US|thumb]]
Basalt is composed mostly of oxides of silicon, iron, magnesium, potassium, aluminum, titanium, and calcium. [[Geologists]] classify [[igneous rock]] by its mineral content whenever possible; the relative volume percentages of [[quartz]] (crystalline [[silica]] (SiO<sub>2</sub>)), [[alkali feldspar]], [[plagioclase]], and [[feldspathoid]] ([[QAPF diagram|QAPF]]) are particularly important. An [[aphanitic]] (fine-grained) igneous rock is classified as basalt when its QAPF fraction is composed of less than 10% feldspathoid and less than 20% quartz, and plagioclase makes up at least 65% of its feldspar content. This places basalt in the basalt/andesite field of the QAPF diagram. Basalt is further distinguished from andesite by its silica content of under 52%.<ref name="lebas-streckeisen-1991">{{Cite journal|last1=Le Bas|first1=M. J.|last2=Streckeisen|first2=A. L.|title=The IUGS systematics of igneous rocks|journal=Journal of the Geological Society|volume=148|issue=5|pages=825–833|doi=10.1144/gsjgs.148.5.0825|bibcode=1991JGSoc.148..825L|year=1991|citeseerx=10.1.1.692.4446|s2cid=28548230}}</ref><ref name="bgs">{{Cite journal|date=1999|title=Rock Classification Scheme - Vol 1 - Igneous|url=http://nora.nerc.ac.uk/id/eprint/3223/1/RR99006.pdf |archive-url=https://web.archive.org/web/20180329022649/http://nora.nerc.ac.uk/id/eprint/3223/1/RR99006.pdf |archive-date=2018-03-29 |url-status=live|journal=British Geological Survey: Rock Classification Scheme|volume=1|pages=1–52}}</ref><ref>{{Cite web|url=http://geology.csupomona.edu/alert/igneous/igclass.htm|title=CLASSIFICATION OF IGNEOUS ROCKS|archive-url=https://web.archive.org/web/20110930102012/http://geology.csupomona.edu/alert/igneous/igclass.htm|archive-date=30 September 2011|url-status=dead}}</ref>{{sfn|Philpotts|Ague|2009|pp=139–143}}

It is often not practical to determine the mineral composition of volcanic rocks, due to their very small grain size, in which case geologists instead classify the rocks chemically, with particular emphasis on the total content of alkali metal oxides and silica ([[TAS classification|TAS]]); in that context, basalt is defined as volcanic rock with a content of between 45% and 52% silica and no more than 5% alkali metal oxides. This places basalt in the B field of the TAS diagram.<ref name="lebas-streckeisen-1991"/><ref name="bgs"/>{{sfn|Philpotts|Ague|2009|pp=139–143}} Such a composition is described as [[mafic]].<ref>{{cite web |url=http://www.glossary.oilfield.slb.com/en/Terms/m/mafic.aspx |publisher=Schlumberger Ltd. |title=Oilfield Glossary |year=2021}}</ref>

Basalt is usually dark grey to black in colour, due to a high content of [[augite]] or other dark-coloured [[pyroxene]] minerals,{{sfn|Hyndman|1985|p={{pn|date=June 2021}}}}{{sfn|Blatt|Tracy|1996|p=57}}{{sfn|Levin|2010|p=63}} but can exhibit a wide range of shading. Some basalts are quite light-coloured due to a high content of plagioclase; these are sometimes described as ''leucobasalts''.<ref name="wilson-1985">{{cite journal |last1=Wilson |first1=F. H. |title=The Meshik Arc – an eocene to earliest miocene magmatic arc on the Alaska Peninsula |date=1985 |pages=PR 88 |doi=10.14509/2269|doi-access=free |journal=Alaska Division of Geological & Geophysical Surveys Professional Report |volume=88|bibcode=1985usgs.rept....1W }}</ref><ref name="nozhkin-etal-2016">{{cite journal |last1=Nozhkin |first1=A.D. |last2=Turkina |first2=O.M. |last3=Likhanov |first3=I.I. |last4=Dmitrieva |first4=N.V. |title=Late Paleoproterozoic volcanic associations in the southwestern Siberian craton (Angara-Kan block) |journal=Russian Geology and Geophysics |date=February 2016 |volume=57 |issue=2 |pages=247–264 |doi=10.1016/j.rgg.2016.02.003|bibcode=2016RuGG...57..247N }}</ref> It can be difficult to distinguish between lighter-colored basalt and [[andesite]], so [[field research]]ers commonly use a [[wiktionary:rule of thumb|rule of thumb]] for this purpose, classifying it as basalt if it has a [[color index (geology)|color index]] of 35 or greater.{{sfn|Philpotts|Ague|2009|p=139}}

The physical properties of basalt result from its relatively low silica content and typically high iron and magnesium content.<ref name="USGSGlossary">{{cite web | url=https://volcanoes.usgs.gov/vsc/glossary/basalt.html | title=Basalt | publisher=[[USGS]] | website=USGS Volcano Hazards program – Glossary | date=8 April 2015 | access-date=27 July 2018}}</ref> The average density of basalt is 2.9 g/cm<sup>3</sup>, compared, for example, to [[granite]]’s typical density of 2.7 g/cm<sup>3</sup>.{{sfn|Philpotts|Ague|2009|p=22}} The viscosity of basaltic magma is relatively low—around 10<sup>4</sup> to 10<sup>5</sup> [[Centipoise|cP]]—similar to the viscosity of [[ketchup]], but that is still several orders of magnitude higher than the viscosity of water, which is about 1 cP).{{sfn|Philpotts|Ague|2009|pp=23–25}}

Basalt is often [[porphyritic]], containing larger crystals ([[phenocryst]]s) that formed before the extrusion event that brought the magma to the surface, embedded in a finer-grained [[Matrix (geology)|matrix]]. These phenocrysts are usually made of augite, [[olivine]], or a calcium-rich plagioclase,{{sfn|Blatt|Tracy|1996|p=57}} which have [[Bowen's reaction series|the highest melting temperatures]] of any of the [[mineral]]s that can typically crystallize from the melt, and which are therefore the first to form solid crystals.{{sfn|Klein|Hurlbut|1993|pp=558–560}}<ref>{{cite web |last1=Nave |first1=R. |title=Bowen's Reaction Series |url=http://hyperphysics.phy-astr.gsu.edu/hbase/Geophys/Bowen.html |website=Hyperphysics |publisher=Georgia State University |access-date=24 March 2021}}</ref>

Basalt often contains [[vesicular texture|vesicles]]; they are formed when dissolved gases bubble out of the magma as it decompresses during its approach to the surface; the erupted lava then solidifies before the gases can escape. When vesicles make up a substantial fraction of the volume of the rock, the rock is described as [[scoria]].{{sfn|Blatt|Tracy|1996|pp=27, 42–44}}<ref>{{cite web |last1=Jones |first1=C.E. |title=Scoria and Pumice |url=https://www.pitt.edu/~cejones/GeoImages/2IgneousRocks/IgneousTextures/8PumiceScoria.html |website=Department of Geology & Planetary Science |publisher=University of Pittsburgh |access-date=24 March 2021}}</ref>

The term ''basalt'' is at times applied to shallow [[intrusive rock]]s with a composition typical of basalt, but rocks of this composition with a [[phaneritic]] (coarser) groundmass are more properly referred to either as [[diabase]] (also called dolerite) or—when they are more coarse-grained (having crystals over 2&nbsp;mm across)—as [[gabbro]]. Diabase and gabbro are thus the [[hypabyssal]] and [[plutonic]] equivalents of basalt.<ref name="bgs"/>{{sfn|Levin|2010|pp=58–60}}
[[File:Szentgyörgyhegy03.jpg|thumb|upright|Columnar basalt at Szent György Hill, Hungary]]
During the [[Hadean]], [[Archean]], and early [[Proterozoic]] [[Eon (geology)|eon]]s of Earth's history, the chemistry of erupted magmas was significantly different from what it is today, due to immature crustal and [[asthenosphere]] differentiation. The resulting [[Ultramafic rock|ultramafic]] volcanic rocks, with silica (SiO<sub>2</sub>) contents below 45% and high magnesium oxide (MgO) content, are usually classified as [[komatiite]]s.{{sfn|Philpotts|Ague|2009|pp=399–400}}<ref>{{cite web |title=Komatiite |url=http://www.atlas-hornin.sk/en/record/54/komatiite |website=Atlas of Magmatic Rocks |publisher=Comenius University in Bratislava |access-date=24 March 2021}}</ref>

=== Etymology ===
The word "basalt" is ultimately derived from [[Late Latin]] {{Lang|la|basaltes}}, a misspelling of Latin {{Lang|la|basanites}} "very [[Hardness|hard]] stone", which was imported from [[Ancient Greek]] {{Lang|grc|βασανίτης}} ({{Transliteration|grc|basanites}}), from {{Lang|grc|βάσανος}} (''{{Transliteration|grc|basanos}}'', "[[touchstone (assaying tool)|touchstone]]").<ref>{{cite journal |last1=Tietz |first1=O. |last2=Büchner |first2=J. |title=The origin of the term 'basalt' |journal=Journal of Geosciences |date=29 December 2018 |pages=295–298 |doi=10.3190/jgeosci.273|doi-access=free }}</ref> The modern petrological term ''basalt'', describing a particular composition of [[lava]]-derived rock, became standard because of its use by [[Georgius Agricola]] in 1546, in his work ''[[De Natura Fossilium]]''. Agricola applied the term "basalt" to the volcanic black rock beneath the [[Bishop of Dresden-Meissen|Bishop of Meissen's]] [[Stolpen#Burg Stolpen|Stolpen castle]], believing it to be the same as the "basaniten" described by [[Pliny the Elder]] in AD&nbsp;77 in {{Lang|la|[[Natural History (Pliny)|Naturalis Historiae]]}}.<ref>{{cite journal |last1=Tietz |first1=Olaf |last2=Büchner |first2=Joerg |title=The origin of the term 'basalt' |journal=Journal of Geosciences |date=2018 |volume=63 |issue=4 |pages=295–298 |doi=10.3190/jgeosci.273 |url=http://www.jgeosci.org/content/jgeosci.273_tietz.pdf |archive-url=https://web.archive.org/web/20190428204828/http://www.jgeosci.org/content/jgeosci.273_tietz.pdf |archive-date=2019-04-28 |url-status=live |access-date=19 August 2020|doi-access=free }}</ref>

=== Types ===
[[File:Causeway23.jpg|thumb|Large masses must cool slowly to form a polygonal joint pattern, as here at the [[Giant's Causeway]] in Northern Ireland]]
[[File:Базальтове.jpg|thumb|right|Columns of basalt near [[Bazaltove]], Ukraine]]

On Earth, most basalt is formed by [[decompression melting]] of the [[mantle (geology)|mantle]].{{sfn|Philpotts|Ague|2009|pp=16–17}} The high pressure in the upper mantle (due to [[Overburden pressure|the weight of the overlying rock]]) raises the melting point of mantle rock, so that almost all of the upper mantle is solid. However, mantle rock is [[ductile]] (the solid rock slowly deforms under high stress). When [[Tectonics|tectonic forces]] cause hot mantle rock to creep upwards, pressure on the ascending rock decreases, and this can lower its melting point enough for the rock to [[Partial melting|partially melt]], producing basaltic magma.<ref name="green-ringwood-1969">{{cite book |doi=10.1029/GM013p0489 |chapter=The Origin of Basalt Magmas |title=The Earth's Crust and Upper Mantle |series=Geophysical Monograph Series |year=2013 |last1=Green |first1=D. H. |last2=Ringwood |first2=A. E. |volume=13 |pages=489–495 |isbn=978-1-118-66897-9 |bibcode=1969GMS....13..489G }}</ref>

Decompression melting can occur in a variety of [[tectonic setting]]s, including in continental [[rift]] zones, at [[Mid-ocean ridge|mid-ocean ridges]], above [[Hotspot (geology)|geological hotspots]],{{sfn|Blatt|Tracy|1996|pp=151–156, 191–195, 162–163, 200}}{{sfn|Philpotts|Ague|2009|pp=236, 593–595}} and in [[back-arc basins]].<ref>{{cite journal |last1=Stern |first1=Robert J. |title=Subduction zones |journal=Reviews of Geophysics |date=2002 |volume=40 |issue=4 |pages=1012 |doi=10.1029/2001RG000108 |bibcode=2002RvGeo..40.1012S |s2cid=15347100 |doi-access=free }}</ref> Basalt also forms in [[subduction zones]], where mantle rock rises into a [[mantle wedge]] above the descending slab. The slab releases water vapor and other volatiles as it descends, which further lowers the melting point, further increasing the amount of decompression melting.{{sfn|Stern|2002|p=22–24}} Each tectonic setting produces basalt with its own distinctive characteristics.{{sfn|Philpotts|Ague|2009|pp=356–361}}  

* [[Tholeiitic basalt]], which is relatively rich in [[iron]] and poor in [[alkali metal]]s and [[aluminium]],{{sfn|Philpotts|Ague|2009|pp=143–146}} include most basalts of the [[ocean]] floor, most large [[oceanic island]]s,{{sfn|Philpotts|Ague|2009|pp=365–370}} and continental [[flood basalt]]s such as the [[Columbia River Basalt Group|Columbia River Plateau]].{{sfn|Philpotts|Ague|2009|pp=52–59}}
**High- and low-titanium basalt rocks, which are sometimes classified based on their [[titanium]] (Ti) content in High-Ti and Low-Ti varieties. High-Ti and Low-Ti basalt have been distinguished from each other in the [[Paraná and Etendeka traps]]<ref>{{cite journal |last1=Gibson |first1=S. A. |last2=Thompson |first2=R. N. |last3=Dickin |first3=A. P. |last4=Leonardos |first4=O. H. |title=High-Ti and low-Ti mafic potassic magmas: Key to plume-lithosphere interactions and continental flood-basalt genesis |journal=Earth and Planetary Science Letters |date=December 1995 |volume=136 |issue=3–4 |pages=149–165 |doi=10.1016/0012-821X(95)00179-G |bibcode=1995E&PSL.136..149G }}</ref> and the [[Emeishan Traps]].<ref name="cugb">{{cite journal |last1=Hou |first1=Tong |last2=Zhang |first2=Zhaochong |last3=Kusky |first3=Timothy |last4=Du |first4=Yangsong |last5=Liu |first5=Junlai |last6=Zhao |first6=Zhidan |title=A reappraisal of the high-Ti and low-Ti classification of basalts and petrogenetic linkage between basalts and mafic–ultramafic intrusions in the Emeishan Large Igneous Province, SW China |journal=Ore Geology Reviews |date=October 2011 |volume=41 |issue=1 |pages=133–143 |doi=10.1016/j.oregeorev.2011.07.005 |bibcode=2011OGRv...41..133H }}</ref>
** [[Mid-ocean ridge]] basalt (MORB) is a tholeiitic basalt that has almost exclusively erupted at ocean ridges; it is characteristically low in [[incompatible element]]s.{{sfn|Blatt|Tracy|1996|pp=156–158}}{{sfn|Hyndman|1985|p={{pn|date=June 2021}}}} Although all MORBs are chemically similar, geologists recognize that they vary significantly in how depleted they are in incompatible elements. When they are present in close proximity along mid-ocean ridges, that is seen as evidence for mantle inhomogeneity.<ref>{{cite journal |last1=Waters |first1=Christopher L. |last2=Sims |first2=Kenneth W. W. |last3=Perfit |first3=Michael R. |last4=Blichert-Toft |first4=Janne |author4-link=Janne Blichert-Toft |last5=Blusztajn |first5=Jurek |title=Perspective on the Genesis of E-MORB from Chemical and Isotopic Heterogeneity at 9–10°N East Pacific Rise |journal=Journal of Petrology |date=March 2011 |volume=52 |issue=3 |pages=565–602 |doi=10.1093/petrology/egq091 |doi-access=free }}</ref>
***Enriched MORB (E-MORB) is defined as MORB that is relatively undepleted in incompatible elements. It was once thought to be mostly located in hot spots along mid-ocean ridges, such as Iceland, but it is now known to be located in many other places along those ridges.<ref>{{cite journal |last1=Donnelly |first1=Kathleen E. |last2=Goldstein |first2=Steven L. |last3=Langmuir |first3=Charles H. |last4=Spiegelman |first4=Marc |title=Origin of enriched ocean ridge basalts and implications for mantle dynamics |journal=Earth and Planetary Science Letters |date=October 2004 |volume=226 |issue=3–4 |pages=347–366 |doi=10.1016/j.epsl.2004.07.019|bibcode=2004E&PSL.226..347D }}</ref>
***Normal MORB (N-MORB) is defined as MORB that has an average amount of incompatible elements.
***D-MORB, depleted MORB, is defined as MORB that is highly depleted in incompatible elements.
* [[Alkali basalt]] is relatively rich in alkali metals. It is [[normative mineralogy|silica-undersaturated]] and may contain [[feldspathoid]]s,{{sfn|Philpotts|Ague|2009|pp=143–146}} [[alkali feldspar]], [[phlogopite]], and [[kaersutite]]. Augite in alkali basalts is titanium-enriched augite; low-calcium pyroxenes are never present.{{sfn|Blatt|Tracy|1996|p=75}} They are characteristic of continental rifting and hotspot volcanism.{{sfn|Philpotts|Ague|2009|pp=368–370, 390–394}}
* High-alumina basalt has greater than 17% [[alumina]] (Al<sub>2</sub>O<sub>3</sub>) and is intermediate in composition between tholeiitic basalt and alkali basalt. Its relatively alumina-rich composition is based on rocks without phenocrysts of [[plagioclase]]. These represent the low-silica end of the [[calc-alkaline magma series]] and are characteristic of [[volcanic arc]]s above subduction zones.{{sfn|Philpotts|Ague|2009|pp=375–376}}
* [[Boninite]] is a high-[[magnesium]] form of basalt that is erupted generally in [[back-arc basin]]s; it is distinguished by its low titanium content and trace-element composition.{{sfn|Crawford|1989|p={{pn|date=June 2021}}}}
* [[Ocean island basalt]]s include both tholeiites and alkali basalts; the tholeiites predominate early in the eruptive history of the island. These basalts are characterized by elevated concentrations of incompatible elements, which suggests that their source mantle rock has produced little magma in the past (it is ''undepleted'').{{sfn|Philpotts|Ague|2009|pp=368–370}}

== Petrology ==
[[File:Мікрофотографія шліфа базальту із заповідника Базальтові стовпи в поляризованому світлі.jpg|thumb|[[Photomicrograph]] of a [[thin section]] of basalt from [[Bazaltove]], Ukraine]]
The mineralogy of basalt is characterized by a preponderance of calcic plagioclase [[feldspar]] and [[pyroxene]]. [[Olivine]] can also be a significant constituent.{{sfn|Levin|2010|p=62}} Accessory [[mineral]]s present in relatively minor amounts include [[iron oxide]]s and iron-titanium oxides, such as [[magnetite]], [[ulvöspinel]], and [[ilmenite]].{{sfn|Blatt|Tracy|1996|p=75}} Because of the presence of such [[oxide]] minerals, basalt can acquire strong [[magnetism|magnetic]] signatures as it cools, and [[paleomagnetism|paleomagnetic]] studies have made extensive use of basalt.{{sfn|Levin|2010|p=185}}

In [[tholeiitic basalt]], pyroxene ([[augite]] and [[orthopyroxene]] or [[pigeonite]]) and [[calcium]]-rich plagioclase are common phenocryst minerals. Olivine may also be a phenocryst, and when present, may have rims of pigeonite. The [[groundmass]] contains interstitial quartz or [[tridymite]] or [[cristobalite]]. ''Olivine tholeiitic basalt'' has augite and orthopyroxene or pigeonite with abundant olivine, but olivine may have rims of pyroxene and is unlikely to be present in the [[matrix (geology)|groundmass]].{{sfn|Blatt|Tracy|1996|p=75}}

[[Alkali basalt]]s typically have mineral assemblages that lack orthopyroxene but contain olivine. Feldspar phenocrysts typically are [[labradorite]] to [[andesine]] in composition. Augite is rich in titanium compared to augite in tholeiitic basalt. Minerals such as [[feldspar|alkali feldspar]], [[leucite]], [[nepheline]], [[sodalite]], [[phlogopite]] mica, and [[apatite]] may be present in the groundmass.{{sfn|Blatt|Tracy|1996|p=75}}

Basalt has high [[liquidus]] and [[Solidus (chemistry)|solidus]] temperatures—values at the Earth's surface are near or above 1200&nbsp;°C (liquidus){{sfn|McBirney|1984|pp=366–367}} and near or below 1000&nbsp;°C (solidus); these values are higher than those of other common igneous rocks.{{sfn|Philpotts|Ague|2009|p=252}}

The majority of tholeiitic basalts are formed at approximately 50–100&nbsp;km depth within the mantle. Many alkali basalts may be formed at greater depths, perhaps as deep as 150–200&nbsp;km.<ref>{{cite book |doi=10.1016/B978-075063386-4/50003-3 |chapter=Tectonic settings |title=Plate Tectonics and Crustal Evolution |year=1997 |last1=Condie |first1=Kent C. |pages=69–109 |isbn=978-0-7506-3386-4 }}</ref><ref>{{cite journal |last1=Kushiro |first1=Ikuo |title=Origin of magmas in subduction zones: a review of experimental studies |journal=Proceedings of the Japan Academy, Series B |date=2007 |volume=83 |issue=1 |pages=1–15 |doi=10.2183/pjab.83.1 |pmid=24019580 |pmc=3756732 |bibcode=2007PJAB...83....1K }}</ref> The origin of high-alumina basalt continues to be controversial, with disagreement over whether it is a [[magma|primary melt]] or derived from other basalt types by fractionation.<ref>{{cite journal|last1=Ozerov|first1=Alexei Y|title=The evolution of high-alumina basalts of the Klyuchevskoy volcano, Kamchatka, Russia, based on microprobe analyses of mineral inclusions|journal=Journal of Volcanology and Geothermal Research|date=January 2000|volume=95|issue=1–4|pages=65–79|doi=10.1016/S0377-0273(99)00118-3|bibcode=2000JVGR...95...65O|url=http://repo.kscnet.ru/2569/1/my_2000_f_en_JVGR.pdf |archive-url=https://web.archive.org/web/20200306105257/http://repo.kscnet.ru/2569/1/my_2000_f_en_JVGR.pdf |archive-date=2020-03-06 |url-status=live}}</ref>{{rp|65}}

=== Geochemistry ===
Relative to most common igneous rocks, basalt compositions are rich in [[magnesium oxide|MgO]] and [[calcium oxide|CaO]] and low in [[silicon dioxide|SiO<sub>2</sub>]] and the alkali oxides, i.e., [[sodium oxide|Na<sub>2</sub>O]] + [[potassium oxide|K<sub>2</sub>O]], consistent with their [[TAS classification]]. Basalt contains more silica than [[picrobasalt]] and most [[basanite]]s and [[tephrite]]s but less than [[basaltic andesite]]. Basalt has a lower total content of alkali oxides than [[trachybasalt]] and most basanites and tephrites.{{sfn|Philpotts|Ague|2009|pp=139–143}}

Basalt generally has a composition of 45–52 [[wt%]] SiO<sub>2</sub>, 2–5 wt% total alkalis,{{sfn|Philpotts|Ague|2009|pp=139–143}} 0.5–2.0 wt% [[titanium dioxide|TiO<sub>2</sub>]], 5–14 wt% [[iron(II) oxide|FeO]] and 14 wt% or more [[alumina|Al<sub>2</sub>O<sub>3</sub>]]. Contents of CaO are commonly near 10 wt%, those of MgO commonly in the range 5 to 12 wt%.<ref name="irvine-baragar-1971">{{cite journal |last1=Irvine |first1=T. N. |last2=Baragar |first2=W. R. A. |title=A Guide to the Chemical Classification of the Common Volcanic Rocks |journal=Canadian Journal of Earth Sciences |date=1 May 1971 |volume=8 |issue=5 |pages=523–548 |doi=10.1139/e71-055|bibcode=1971CaJES...8..523I }}</ref>

High-alumina basalts have aluminium contents of 17–19 wt% Al<sub>2</sub>O<sub>3</sub>; [[boninite]]s have [[magnesium]] (MgO) contents of up to 15 percent. Rare [[feldspathoid]]-rich [[mafic]] rocks, akin to alkali basalts, may have Na<sub>2</sub>O + K<sub>2</sub>O contents of 12% or more.{{sfn|Irvine|Baragar|1971}}

The abundances of the [[lanthanide]] or [[rare-earth element]]s (REE) can be a useful diagnostic tool to help explain the history of mineral crystallisation as the melt cooled. In particular, the relative abundance of europium compared to the other REE is often markedly higher or lower, and called the [[europium anomaly]]. It arises because Eu<sup>2+</sup> can substitute for Ca<sup>2+</sup> in plagioclase feldspar, unlike any of the other lanthanides, which tend to only form <sup>3+</sup> [[cation]]s.{{sfn|Philpotts|Ague|2009|p=359}}

Mid-ocean ridge basalts (MORB) and their intrusive equivalents, gabbros, are the characteristic igneous rocks formed at mid-ocean ridges. They are tholeiitic basalts particularly low in total alkalis and in [[Compatibility (geochemistry)|incompatible]] trace elements, and they have relatively flat REE patterns normalized to mantle or [[chondrite]] values. In contrast, alkali basalts have normalized patterns highly enriched in the light REE, and with greater abundances of the REE and of other incompatible elements. Because MORB basalt is considered a key to understanding [[plate tectonics]], its compositions have been much studied. Although MORB compositions are distinctive relative to average compositions of basalts erupted in other environments, they are not uniform. For instance, compositions change with position along the [[Mid-Atlantic Ridge]], and the compositions also define different ranges in different ocean basins.<ref>{{cite book |doi=10.1016/B978-0-08-095975-7.00203-5 |chapter=Sampling Mantle Heterogeneity through Oceanic Basalts: Isotopes and Trace Elements |title=Treatise on Geochemistry |year=2014 |last1=Hofmann |first1=A.W. |pages=67–101 |isbn=978-0-08-098300-4 }}</ref> Mid-ocean ridge basalts have been subdivided into varieties such as normal (NMORB) and those slightly more enriched in incompatible elements (EMORB).{{sfn|Philpotts|Ague|2009|p=312}}

[[Isotope]] ratios of [[chemical element|elements]] such as [[strontium]], [[neodymium]], [[lead]], [[hafnium]], and [[osmium]] in basalts have been much studied to learn about the evolution of the [[Earth's mantle]].{{sfn|Philpotts|Ague|2009|loc=Chapter 13}} Isotopic ratios of [[noble gas]]es, such as <sup>3</sup>[[Helium|He]]/<sup>4</sup>He, are also of great value: for instance, ratios for basalts range from 6 to 10 for mid-ocean ridge tholeiitic basalt (normalized to atmospheric values), but to 15–24 and more for ocean-island basalts thought to be derived from [[mantle plume]]s.<ref name="class-goldstein-2005">{{cite journal |last1=Class |first1=Cornelia |last2=Goldstein |first2=Steven L. |title=Evolution of helium isotopes in the Earth's mantle |journal=Nature |date=August 2005 |volume=436 |issue=7054 |pages=1107–1112 |doi=10.1038/nature03930|pmid=16121171 |bibcode=2005Natur.436.1107C |s2cid=4396462 }}</ref>

Source rocks for the partial melts that produce basaltic magma probably include both [[peridotite]] and [[pyroxenite]].<ref name="sobolev-etal-2007">{{cite journal|author=Alexander V. Sobolev|author2=Albrecht W. Hofmann|author3=Dmitry V. Kuzmin|author4=Gregory M. Yaxley|author5=Nicholas T. Arndt|author6-link=Sun-Lin Chung|author6=Sun-Lin Chung|author7=Leonid V. Danyushevsky|author8=Tim Elliott|author9=Frederick A. Frey|author10=Michael O. Garcia|author11=Andrey A. Gurenko|author12=Vadim S. Kamenetsky|author13=Andrew C. Kerr|author14=Nadezhda A. Krivolutskaya|author15=Vladimir V. Matvienkov|author16=Igor K. Nikogosian|author17=Alexander Rocholl|author18=Ingvar A. Sigurdsson|author19=Nadezhda M. Sushchevskaya|author20=Mengist Teklay|name-list-style=amp |title=The Amount of Recycled Crust in Sources of Mantle-Derived Melts|journal=Science|date=20 April 2007|volume=316|issue=5823|pages=412–417|bibcode=2007Sci...316..412S|doi=10.1126/science.x|pmid=17395795|url=http://eprints.utas.edu.au/2614/1/Science2007.pdf}}
</ref>

=== Morphology and textures ===
[[File:20011005-0039 DAS large.jpg|thumb|An active basalt lava flow]]
The shape, structure and [[rock microstructure|texture]] of a basalt is diagnostic of how and where it erupted—for example, whether into the sea, in an explosive [[Scoria|cinder]] eruption or as creeping [[pāhoehoe]] lava flows, the classic image of [[Hawaii]]an basalt eruptions.{{sfn|Schmincke|2003|p={{pn|date=June 2021}}}}

==== Subaerial eruptions ====
{{Main|Subaerial eruption}}
Basalt that erupts under open air (that is, [[subaerial]]ly) forms three distinct types of lava or volcanic deposits: [[scoria]]; [[volcanic ash|ash]] or cinder ([[breccia]]);{{sfn|Blatt|Tracy|1996|pp=27–28}} and lava flows.{{sfn|Blatt|Tracy|1996|pp=22–23}}

Basalt in the tops of subaerial lava flows and [[cinder cone]]s will often be highly [[Vesicular texture|vesiculated]], imparting a lightweight "frothy" texture to the rock.{{sfn|Blatt|Tracy|1996|pp=43–44}} Basaltic cinders are often red, coloured by oxidized [[iron]] from weathered iron-rich minerals such as [[pyroxene]].{{sfn|Lillie|2005|p=41}}

[[Lava#{{okina}}A{{okina}}ā|{{okina}}A{{okina}}ā]] types of blocky cinder and breccia flows of thick, viscous basaltic [[lava]] are common in Hawai{{okina}}i. Pāhoehoe is a highly fluid, hot form of basalt which tends to form thin aprons of molten lava which fill up hollows and sometimes forms [[lava lake]]s. [[Lava tube]]s are common features of pāhoehoe eruptions.{{sfn|Blatt|Tracy|1996|pp=22–23}}

Basaltic [[tuff]] or [[Pyroclastic rock|pyroclastic]] rocks are less common than basaltic lava flows. Usually basalt is too hot and fluid to build up sufficient pressure to form explosive lava eruptions but occasionally this will happen by trapping of the lava within the volcanic throat and buildup of [[volcanic gas]]es. Hawai{{okina}}i's [[Mauna Loa]] volcano erupted in this way in the 19th century, as did [[Mount Tarawera]], New Zealand in its violent 1886 eruption. [[Maar]] volcanoes are typical of small basalt tuffs, formed by explosive eruption of basalt through the crust, forming an apron of mixed basalt and wall rock breccia and a fan of basalt tuff further out from the volcano.{{sfn|Schmincke|2003|loc=Chapter 12}}

Amygdaloidal structure is common in relict [[vesicle (geology)|vesicles]] and beautifully [[crystal]]lized species of [[zeolite]]s, [[quartz]] or [[calcite]] are frequently found.{{sfn|Philpotts|Ague|2009|p=64}}

===== Columnar basalt =====
{{Main|Columnar jointing}}
{{See also|List of places with columnar basalt}}
[[File:Causeway-code poet-4.jpg|thumb|The [[Giant's Causeway]] in Northern Ireland]]
[[File:Boyabat.jpg|thumb|Columnar [[Joint (geology)|jointed]] basalt in [[Turkey]]]]
[[File:Мыс Столбчатый. После заката.jpg|thumb|Columnar basalt at [[Cape Stolbchaty]], Russia]]
During the cooling of a thick lava flow, contractional [[Joint (geology)|joints]] or fractures form.<ref>{{cite journal |last1=Smalley |first1=I. J. |title=Contraction Crack Networks in Basalt Flows |journal=Geological Magazine |date=April 1966 |volume=103 |issue=2 |pages=110–114 |doi=10.1017/S0016756800050482 |bibcode=1966GeoM..103..110S |s2cid=131237003 }}</ref> If a flow cools relatively rapidly, significant [[Thermal expansion#Contraction effects (negative expansion)|contraction]] forces build up. While a flow can shrink in the vertical dimension without fracturing, it cannot easily accommodate shrinking in the horizontal direction unless cracks form; the extensive fracture network that develops results in the formation of [[Columnar jointing|column]]s. These structures, or [[basalt prism]]s, are predominantly hexagonal in cross-section, but polygons with three to twelve or more sides can be observed.<ref>{{cite journal |last1=Weaire |first1=D. |last2=Rivier |first2=N. |title=Soap, cells and statistics—random patterns in two dimensions |journal=Contemporary Physics |date=January 1984 |volume=25 |issue=1 |pages=59–99 |doi=10.1080/00107518408210979 |bibcode=1984ConPh..25...59W }}</ref> The size of the columns depends loosely on the rate of cooling; very rapid cooling may result in very small (<1&nbsp;cm diameter) columns, while slow cooling is more likely to produce large columns.<ref name="spry-1962">{{cite journal |last1=Spry |first1=Alan |title=The origin of columnar jointing, particularly in basalt flows |journal=Journal of the Geological Society of Australia |date=January 1962 |volume=8 |issue=2 |pages=191–216 |doi=10.1080/14400956208527873 |bibcode=1962AuJES...8..191S }}</ref>

==== Submarine eruptions ====
{{Main|Submarine eruption}}
[[File:Pillow basalt crop l.jpg|thumb|Pillow basalts on the Pacific seafloor]]

The character of submarine basalt eruptions is largely determined by depth of water, since increased pressure restricts the release of volatile gases and results in effusive eruptions.<ref name="francis">Francis, P. (1993) ''Volcanoes: A Planetary Perspective'', Oxford University Press.</ref> It has been estimated that at depths greater than {{convert|500|m||}}, explosive activity associated with basaltic magma is suppressed.{{sfn|Parfitt|Parfitt|Wilson|2008|p={{pn|date=June 2021}}}} Above this depth, submarine eruptions are often explosive, tending to produce [[pyroclastic rock]] rather than basalt flows.<ref name="head and wilson">{{cite journal |last1=Head |first1=James W. |last2=Wilson |first2=Lionel |title=Deep submarine pyroclastic eruptions: theory and predicted landforms and deposits |journal=Journal of Volcanology and Geothermal Research |date=2003 |volume=121 |issue=3–4 |pages=155–193 |doi=10.1016/S0377-0273(02)00425-0 |bibcode=2003JVGR..121..155H }}</ref> These eruptions, described as Surtseyan, are characterised by large quantities of steam and gas and the creation of large amounts of [[pumice]].<ref name="Smithson">[http://www.volcano.si.edu/galleries.cfm?p=11], Smithsonian Institution National Museum of Natural History Global Volcanism Program (2013).</ref> 

===== Pillow basalts =====
{{Main|Pillow lava}}
When basalt erupts underwater or flows into the sea, contact with the water quenches the surface and the lava forms a distinctive ''pillow'' shape, through which the hot lava breaks to form another pillow. This "pillow" texture is very common in underwater basaltic flows and is diagnostic of an underwater eruption environment when found in ancient rocks. Pillows typically consist of a fine-grained core with a glassy crust and have radial jointing. The size of individual pillows varies from 10&nbsp;cm up to several metres.{{sfn|Schmincke|2003|p=64}}

When ''[[pahoehoe|pāhoehoe]]'' lava enters the sea it usually forms pillow basalts. However, when ''{{okina}}a{{okina}}ā'' enters the ocean it forms a [[littoral cone]], a small cone-shaped accumulation of tuffaceous debris formed when the blocky ''{{okina}}a{{okina}}ā'' lava enters the water and explodes from built-up steam.{{sfn|Macdonald|Abbott|Peterson|1983|p={{pn|date=June 2021}}}}

The island of [[Surtsey]] in the [[Atlantic Ocean]] is a basalt volcano which breached the ocean surface in 1963. The initial phase of Surtsey's eruption was highly explosive, as the magma was quite fluid, causing the rock to be blown apart by the boiling steam to form a tuff and cinder cone. This has subsequently moved to a typical pāhoehoe-type behaviour.<ref name="kikelaar-durant-1983">{{cite journal |last1=Kokelaar |first1=B.Peter |last2=Durant |first2=Graham P. |title=The submarine eruption and erosion of Surtla (Surtsey), Iceland |journal=Journal of Volcanology and Geothermal Research |date=December 1983 |volume=19 |issue=3–4 |pages=239–246 |doi=10.1016/0377-0273(83)90112-9|bibcode=1983JVGR...19..239K }}</ref><ref name="moore-1985">{{cite journal |last1=Moore |first1=James G. |title=Structure and eruptive mechanisms at Surtsey Volcano, Iceland |journal=Geological Magazine |date=November 1985 |volume=122 |issue=6 |pages=649–661 |doi=10.1017/S0016756800032052 |bibcode=1985GeoM..122..649M |s2cid=129242411 }}</ref>

[[Volcanic glass]] may be present, particularly as rinds on rapidly chilled surfaces of lava flows, and is commonly (but not exclusively) associated with underwater eruptions.{{sfn|Blatt|Tracy|1996|pp=24–25}}

Pillow basalt is also produced by some [[Subglacial eruption|subglacial]] volcanic eruptions.{{sfn|Blatt|Tracy|1996|pp=24–25}}

== Distribution ==

===Earth===
Basalt is the most common volcanic rock type on Earth, making up over 90% of all volcanic rock on the planet.<ref name="UnivAuckland">{{cite web | url=https://flexiblelearning.auckland.ac.nz/rocks_minerals/rocks/basalt.html | title=Basalt | publisher=The University of Auckland | website=Geology: rocks and minerals | date=2005 | access-date=27 July 2018}}</ref> The [[crust (geology)|crustal]] portions of [[ocean]]ic [[tectonic plate]]s are composed predominantly of basalt, produced from upwelling mantle below the [[ocean ridge]]s.{{sfn|Philpotts|Ague|2009|pp=366–368}} Basalt is also the principal volcanic rock in many [[oceanic island]]s, including the islands of [[Hawaii (island)|Hawai{{okina}}i]],{{sfn|Philpotts|Ague|2009|pp=365–370}} the [[Faroe Islands]],{{sfn|Schmincke|2003|p=91}} and [[Réunion]].<ref name="upton-wadsworth-1965">{{cite journal |last1=Upton |first1=B. G. J. |last2=Wadsworth |first2=W. J. |title=Geology of Réunion Island, Indian Ocean |journal=Nature |date=July 1965 |volume=207 |issue=4993 |pages=151–154 |doi=10.1038/207151a0 |bibcode=1965Natur.207..151U |s2cid=4144134 }}</ref> The eruption of basalt lava is observed by geologists at about 20 volcanoes per year.<ref name="Walker1993">{{Cite book |last1=Walker |first1=G.P.L. |chapter=Basaltic-volcano systems |editor1-last=Prichard |editor1-first=H.M. |editor2-last=Alabaster |editor2-first=T.  |editor3-last=Harris |editor3-first=N.B.W. |editor4-last=Neary |editor4-first=C.R. |title=Magmatic Processes and Plate Tectonics |pages=3–38 |publisher=The Geological Society |series=Geological Society Special Publication 76 |date=1993 |isbn=978-0-903317-94-8 }}</ref>

[[File:Parana traps.JPG|thumb|[[Paraná Traps]], [[Brazil]]]]
Basalt is the rock most typical of [[large igneous province]]s. These include [[continental flood basalt]]s, the most voluminous basalts found on land.{{sfn|Philpotts|Ague|2009|pp=52–59}} Examples of continental flood basalts included the [[Deccan Traps]] in [[India]],<ref>{{cite book |doi=10.1007/978-94-015-7805-9_5 |chapter=Deccan Traps |title=Continental Flood Basalts |series=Petrology and Structural Geology |year=1988 |last1=Mahoney |first1=John J. |volume=3 |pages=151–194 |isbn=978-90-481-8458-3 }}</ref> the [[Chilcotin Group]] in [[British Columbia]],<ref>{{cite journal |last1=Bevier |first1=Mary Lou |title=Regional stratigraphy and age of Chilcotin Group basalts, south-central British Columbia |journal=Canadian Journal of Earth Sciences |date=1 April 1983 |volume=20 |issue=4 |pages=515–524 |doi=10.1139/e83-049|bibcode=1983CaJES..20..515B }}</ref> [[Canada]], the [[Paraná Traps]] in Brazil,<ref>{{cite journal |last1=Renne |first1=P. R. |last2=Ernesto |first2=M. |last3=Pacca |first3=I. G. |last4=Coe |first4=R. S. |last5=Glen |first5=J. M. |last6=Prevot |first6=M. |last7=Perrin |first7=M. |title=The Age of Parana Flood Volcanism, Rifting of Gondwanaland, and the Jurassic-Cretaceous Boundary |journal=Science |date=6 November 1992 |volume=258 |issue=5084 |pages=975–979 |doi=10.1126/science.258.5084.975|pmid=17794593 |bibcode=1992Sci...258..975R |s2cid=43246541 }}</ref> the [[Siberian Traps]] in [[Russia]],<ref>{{cite journal |last1=Renne |first1=P. R. |last2=Basu |first2=A. R. |title=Rapid Eruption of the Siberian Traps Flood Basalts at the Permo-Triassic Boundary |journal=Science |date=12 July 1991 |volume=253 |issue=5016 |pages=176–179 |doi=10.1126/science.253.5016.176 |pmid=17779134 |bibcode=1991Sci...253..176R |s2cid=6374682 }}</ref> the [[Karoo]] [[flood basalt]] province in South Africa,<ref>{{cite journal |last1=Jourdan |first1=F. |last2=Féraud |first2=G. |last3=Bertrand |first3=H. |last4=Watkeys |first4=M. K. |title=From flood basalts to the inception of oceanization: Example from the 40 Ar/ 39 Ar high-resolution picture of the Karoo large igneous province |journal=Geochemistry, Geophysics, Geosystems |date=February 2007 |volume=8 |issue=2 |article-number=2006GC001392 |pages=n/a |doi=10.1029/2006GC001392 |bibcode=2007GGG.....8.2002J |doi-access=free }}</ref> and the [[Columbia River Plateau]] of [[Washington (state)|Washington]] and [[Oregon]].<ref>{{cite journal |last1=Hooper |first1=P. R. |title=The Columbia River Basalts |journal=Science |date=19 March 1982 |volume=215 |issue=4539 |pages=1463–1468 |doi=10.1126/science.215.4539.1463 |pmid=17788655 |bibcode=1982Sci...215.1463H |s2cid=6182619 }}</ref> Basalt is also prevalent across extensive regions of the Eastern [[Galilee earthquake of 1837|Galilee]], [[Golan Heights|Golan]], and [[Bashan]] in [[Israel]] and [[Syria]].<ref>{{Cite book |last1=Reich |first1=Ronny |title=The Architecture of Ancient Israel |last2=Katzenstein |first2=Hannah |date=1992 |publisher=Israel Exploration Society |isbn=978-965-221-013-5 |editor-last=Kempinski |editor-first=Aharon |location=Jerusalem |pages=312 |chapter=Glossary of Archaeological Terms |editor-last2=Reich |editor-first2=Ronny }}</ref>

Basalt also is common around volcanic arcs, specially those on thin [[crust (geology)|crust]].{{sfn|Philpotts|Ague|2009|pp=374-380}}

Ancient [[Precambrian]] basalts are usually only found in fold and thrust belts, and are often heavily metamorphosed. These are known as [[greenstone belt]]s,{{sfn|Philpotts|Ague|2009|pp=398–399}}<ref>{{cite journal |last1=Smithies |first1=R. Hugh |last2=Ivanic |first2=Tim J. |last3=Lowrey |first3=Jack R. |last4=Morris |first4=Paul A. |last5=Barnes |first5=Stephen J. |last6=Wyche |first6=Stephen |last7=Lu |first7=Yong-Jun |title=Two distinct origins for Archean greenstone belts |journal=Earth and Planetary Science Letters |date=April 2018 |volume=487 |pages=106–116 |doi=10.1016/j.epsl.2018.01.034 |bibcode=2018E&PSL.487..106S }}</ref> because low-grade [[metamorphism]] of basalt produces [[Chlorite group|chlorite]], [[actinolite]], [[epidote]] and other green minerals.{{sfn|Blatt|Tracy|1996|pp=366-367}}

===Other bodies in the Solar System===
As well as forming large parts of the Earth's crust, basalt also occurs in other parts of the Solar System. Basalt commonly erupts on [[Io (moon)|Io]] (the third largest moon of [[Jupiter]]),<ref name="LopesGregg">{{cite book | title=Volcanic Worlds: Exploring The Solar System's Volcanoes | publisher=Springer-Praxis | last1=Lopes | first1=Rosaly M. C. | author1-link=Rosaly Lopes | last2=Gregg | first2=Tracy K. P. | year=2004 | page=135 | isbn=978-3-540-00431-8}}</ref> and has also formed on the [[Moon]], [[Mars]], [[Venus]], and the asteroid [[4 Vesta|Vesta]].

====The Moon====
[[File:Lunar Olivine Basalt 15555 from Apollo 15 in National Museum of Natural History.jpg|thumb|Lunar [[olivine]] basalt collected by [[Apollo 15]] astronauts]]
The dark areas visible on Earth's [[moon]], the [[lunar mare|lunar maria]], are plains of [[flood basalt]]ic lava flows. These rocks were sampled both by the crewed American [[Apollo program]] and the robotic Russian [[Luna program]], and are represented among the [[lunar meteorite]]s.<ref name="lucey-2006">{{cite journal |last1=Lucey |first1=P. |title=Understanding the Lunar Surface and Space-Moon Interactions |journal=Reviews in Mineralogy and Geochemistry |date=1 January 2006 |volume=60 |issue=1 |pages=83–219 |doi=10.2138/rmg.2006.60.2|bibcode=2006RvMG...60...83L }}</ref>

Lunar basalts differ from their Earth counterparts principally in their high iron contents, which typically range from about 17 to 22 wt% FeO. They also possess a wide range of titanium concentrations (present in the mineral [[ilmenite]]),<ref name="NYT-20151228">{{cite news |last=Bhanoo |first=Sindya N. |title=New Type of Rock Is Discovered on Moon |url=https://www.nytimes.com/2015/12/29/science/new-type-of-rock-is-discovered-on-moon.html |date=28 December 2015 |work=[[The New York Times]] |access-date=29 December 2015 }}</ref><ref>{{cite journal |last1=Ling |first1=Zongcheng |last2=Jolliff |first2=Bradley L. |last3=Wang |first3=Alian |last4=Li |first4=Chunlai |last5=Liu |first5=Jianzhong |last6=Zhang |first6=Jiang |last7=Li |first7=Bo |last8=Sun |first8=Lingzhi |last9=Chen |first9=Jian |last10=Xiao |first10=Long |last11=Liu |first11=Jianjun |last12=Ren |first12=Xin |last13=Peng |first13=Wenxi |last14=Wang |first14=Huanyu |last15=Cui |first15=Xingzhu |last16=He |first16=Zhiping |last17=Wang |first17=Jianyu |title=Correlated compositional and mineralogical investigations at the Chang'e-3 landing site |journal=Nature Communications |date=December 2015 |volume=6 |issue=1 |pages=8880 |doi=10.1038/ncomms9880 |pmid=26694712 |pmc=4703877 |bibcode=2015NatCo...6.8880L |doi-access=free }}</ref> ranging from less than 1 wt% TiO<sub>2</sub>, to about 13 wt.%. Traditionally, lunar basalts have been classified according to their titanium content, with classes being named high-Ti, low-Ti, and very-low-Ti. Nevertheless, global geochemical maps of titanium obtained from the [[Clementine mission]] demonstrate that the lunar maria possess a continuum of titanium concentrations, and that the highest concentrations are the least abundant.<ref name="GiguereEtAl2000">{{cite journal |last1=Giguere |first1=Thomas A. |last2=Taylor |first2=G. Jeffrey |last3=Hawke |first3=B. Ray |last4=Lucey |first4=Paul G. |title=The titanium contents of lunar mare basalts |journal=Meteoritics & Planetary Science |date=January 2000 |volume=35 |issue=1 |pages=193–200 |doi=10.1111/j.1945-5100.2000.tb01985.x |bibcode=2000M&PS...35..193G |doi-access=free }}</ref>

Lunar basalts show exotic textures and mineralogy, particularly [[shock metamorphism]], lack of the [[redox|oxidation]] typical of terrestrial basalts, and a complete lack of [[mineral hydration|hydration]].{{sfn|Lucey|2006}} Most of the [[geology of the Moon|Moon]]'s basalts erupted between about 3 and 3.5 billion years ago, but the oldest samples are 4.2 billion years old, and the youngest flows, based on the age dating method of [[crater counting]], are estimated to have erupted only 1.2 billion years ago.<ref name="hiesinger-etal-200">{{cite journal |last1=Hiesinger |first1=Harald |last2=Jaumann |first2=Ralf |last3=Neukum |first3=Gerhard |last4=Head |first4=James W. |title=Ages of mare basalts on the lunar nearside |journal=Journal of Geophysical Research: Planets |date=25 December 2000 |volume=105 |issue=E12 |pages=29239–29275 |doi=10.1029/2000JE001244 |bibcode=2000JGR...10529239H |doi-access=free }}</ref>

====Venus====
From 1972 to 1985, five [[Venera]] and two [[Vega program|VEGA]] landers successfully reached the surface of Venus and carried out geochemical measurements using X-ray fluorescence and gamma-ray analysis. These returned results consistent with the rock at the landing sites being basalts, including both tholeiitic and highly alkaline basalts. The landers are thought to have landed on plains whose radar signature is that of basaltic lava flows. These constitute about 80% of the surface of Venus. Some locations show high reflectivity consistent with unweathered basalt, indicating basaltic volcanism within the last 2.5 million years.<ref name="gilmore-etal-2017">{{cite journal |last1=Gilmore |first1=Martha |last2=Treiman |first2=Allan |last3=Helbert |first3=Jörn |last4=Smrekar |first4=Suzanne |title=Venus Surface Composition Constrained by Observation and Experiment |journal=Space Science Reviews |date=November 2017 |volume=212 |issue=3–4 |pages=1511–1540 |doi=10.1007/s11214-017-0370-8|bibcode=2017SSRv..212.1511G |s2cid=126225959 }}</ref>

====Mars====
Basalt is also a common rock on the surface of [[Mars]], as determined by data sent back from the planet's surface,<ref name="grotzinger-2013">{{cite journal|last1=Grotzinger|first1=J. P.|title=Analysis of Surface Materials by the Curiosity Mars Rover|journal=Science|date=26 September 2013|volume=341|issue=6153|pages=1475|doi=10.1126/science.1244258|pmid=24072916|bibcode=2013Sci...341.1475G|doi-access=free}}</ref> and by [[Martian meteorite]]s.<ref>{{Cite web  |last1=Choi |first1=Charles Q. |date=11 October 2012| url=http://www.space.com/18014-mars-meteorites-black-glass.html | title=Meteorite's Black Glass May Reveal Secrets of Mars |website=Space.com | publisher=Future US, Inc. |access-date=24 March 2021}}</ref><ref>{{cite journal |last1=Gattacceca |first1=Jérôme |last2=Hewins |first2=Roger H. |last3=Lorand |first3=Jean-Pierre |last4=Rochette |first4=Pierre |last5=Lagroix |first5=France |last6=Cournède |first6=Cécile |last7=Uehara |first7=Minoru |last8=Pont |first8=Sylvain |last9=Sautter |first9=Violaine |author9-link=Violaine Sautter|last10=Scorzelli |first10=Rosa. B. |last11=Hombourger |first11=Chrystel |last12=Munayco |first12=Pablo |last13=Zanda |first13=Brigitte |last14=Chennaoui |first14=Hasnaa |last15=Ferrière |first15=Ludovic |title=Opaque minerals, magnetic properties, and paleomagnetism of the Tissint Martian meteorite |journal=Meteoritics & Planetary Science |date=October 2013 |volume=48 |issue=10 |pages=1919–1936 |doi=10.1111/maps.12172|bibcode=2013M&PS...48.1919G |doi-access=free }}</ref>

====Vesta====
Analysis of [[Hubble Space Telescope]] images of Vesta suggests this [[asteroid]] has a basaltic crust covered with a brecciated [[regolith]] derived from the crust.<ref name="binzel-etal-1997">{{cite journal |last1=Binzel |first1=Richard P |last2=Gaffey |first2=Michael J |last3=Thomas |first3=Peter C |last4=Zellner |first4=Benjamin H |last5=Storrs |first5=Alex D |last6=Wells |first6=Eddie N |title=Geologic Mapping of Vesta from 1994 Hubble Space Telescope Images |journal=Icarus |date=July 1997 |volume=128 |issue=1 |pages=95–103 |doi=10.1006/icar.1997.5734|bibcode=1997Icar..128...95B |doi-access=free }}</ref> Evidence from Earth-based telescopes and the [[Dawn (spacecraft)|Dawn mission]] suggest that Vesta is the source of the [[HED meteorite]]s, which have basaltic characteristics.<ref name="mittlefehldt-2015">{{cite journal |last1=Mittlefehldt |first1=David W. |title=Asteroid (4) Vesta: I. The howardite-eucrite-diogenite (HED) clan of meteorites |journal=Geochemistry |date=June 2015 |volume=75 |issue=2 |pages=155–183 |doi=10.1016/j.chemer.2014.08.002 |bibcode=2015ChEG...75..155M }}</ref> Vesta is the main contributor to the inventory of basaltic asteroids of the main Asteroid Belt.<ref>{{cite journal |last1=Moskovitz |first1=Nicholas A. |last2=Jedicke |first2=Robert |last3=Gaidos |first3=Eric |last4=Willman |first4=Mark |last5=Nesvorný |first5=David |last6=Fevig |first6=Ronald |last7=Ivezić |first7=Željko |title=The distribution of basaltic asteroids in the Main Belt |journal=Icarus |date=November 2008 |volume=198 |issue=1 |pages=77–90 |doi=10.1016/j.icarus.2008.07.006 |arxiv=0807.3951 |bibcode=2008Icar..198...77M |s2cid=38925782 }}</ref>

====Io====
Lava flows represent a major volcanic terrain on [[Io (moon)|Io]].<ref name="Keszthelyi2001">{{cite journal |last1=Keszthelyi |first1=L. |last2=McEwen |first2=A. S. |last3=Phillips |first3=C. B.|author3-link=Cynthia B. Phillips |last4=Milazzo |first4=M. |last5=Geissler |first5=P. |last6=Turtle |first6=E. P. |last7=Radebaugh |first7=J. |last8=Williams |first8=D. A. |last9=Simonelli |first9=D. P. |last10=Breneman |first10=H. H. |last11=Klaasen |first11=K. P. |last12=Levanas |first12=G. |last13=Denk |first13=T. |title=Imaging of volcanic activity on Jupiter's moon Io by Galileo during the Galileo Europa Mission and the Galileo Millennium Mission |journal=Journal of Geophysical Research: Planets |date=2001-12-25 |volume=106 |issue=E12 |pages=33025–33052 |doi=10.1029/2000JE001383 |bibcode=2001JGR...10633025K |doi-access=free }}</ref> Analysis of the ''Voyager'' images led scientists to believe that these flows were composed mostly of various compounds of molten sulfur. However, subsequent Earth-based [[infrared]] studies and measurements from the ''Galileo'' spacecraft indicate that these flows are composed of basaltic lava with mafic to ultramafic compositions.<ref name="Battaglia2019">{{Cite conference |title= A Jökulhlaup-like Model for Secondary Sulfur Flows on Io |conference=50th Lunar and Planetary Science Conference. 18–22 March 2019. The Woodlands, Texas. |first=Steven M. |last=Battaglia |date=March 2019 |id=LPI Contribution No. 1189 |url=https://www.hou.usra.edu/meetings/lpsc2019/pdf/1189.pdf | bibcode=2019LPI....50.1189B}}</ref> This conclusion is based on temperature measurements of Io's "hotspots", or thermal-emission locations, which suggest temperatures of at least 1,300&nbsp;K and some as high as 1,600&nbsp;K.<ref name="Keszthelyi2007">{{cite journal |last1=Keszthelyi |first1=Laszlo |last2=Jaeger |first2=Windy |last3=Milazzo |first3=Moses |last4=Radebaugh |first4=Jani |last5=Davies |first5=Ashley Gerard |last6=Mitchell |first6=Karl L. |title=New estimates for Io eruption temperatures: Implications for the interior |journal=Icarus |date=December 2007 |volume=192 |issue=2 |pages=491–502 |doi=10.1016/j.icarus.2007.07.008 |bibcode=2007Icar..192..491K |url=https://zenodo.org/record/1259031 }}</ref> Initial estimates suggesting eruption temperatures approaching 2,000&nbsp;K<ref name="Mcewen1998b">{{cite journal |title=High-temperature silicate volcanism on Jupiter's moon Io |journal=Science |last=McEwen |first=A. S. |display-authors=etal |pages=87–90 |volume=281 |issue=5373 |date=1998 |doi=10.1126/science.281.5373.87 |pmid=9651251 |bibcode=1998Sci...281...87M |s2cid=28222050 }}</ref> have since proven to be overestimates because the wrong thermal models were used to model the temperatures.<ref name="Keszthelyi2007"/>{{sfn|Battaglia|2019}}

== Alteration of basalt ==

=== Weathering ===
{{See also|Weathering}}
[[File:Absolute iron accumulation in kaolinized basalt. C 015.jpg|thumb|alt=This rock wall shows dark veins of mobilized and precipitated iron within kaolinized basalt in Hungen, Vogelsberg area, Germany.|Kaolinized basalt near Hungen, Vogelsberg, Germany]]

Compared to granitic rocks exposed at the Earth's surface, basalt [[outcrop]]s weather relatively rapidly. This reflects their content of minerals that crystallized at higher temperatures and in an environment poorer in water vapor than granite. These minerals are less stable in the colder, wetter environment at the Earth's surface. The finer grain size of basalt and the [[volcanic glass]] sometimes found between the grains also hasten weathering. The high iron content of basalt causes weathered surfaces in humid climates to accumulate a thick crust of [[hematite]] or other iron oxides and hydroxides, staining the rock a brown to rust-red colour.{{sfn|Blatt|Middleton|Murray|1980|pp=254–257}}<ref name="mackin-1961">{{cite journal |last1=Mackin |first1=J.H. |year=1961 |title=A stratigraphic section in the Yakima Basalt and the Ellensburg Formation in south-central Washington |journal=Washington Division of Mines and Geology Report of Investigations |volume=19 |url=https://www.dnr.wa.gov/Publications/ger_ri19_strat_yakima_basalt_ellensburg_form.pdf |archive-url=https://web.archive.org/web/20100124083749/http://www.dnr.wa.gov/Publications/ger_ri19_strat_yakima_basalt_ellensburg_form.pdf |archive-date=2010-01-24 |url-status=live }}</ref><ref name="usgs-holyoke">{{cite web |title=Holyoke Basalt |url=https://mrdata.usgs.gov/geology/state/sgmc-unit.php?unit=CTJho%3B0 |website=USGS Mineral Resources Program |publisher=United States Geological Survey |access-date=13 August 2020}}</ref><ref name="anderson-1987">{{cite journal |last1=Anderson |first1=J. L. |title=Geologic map of the Goldendale 15' quadrangle, Washington |journal=Washington Division of Geology and Earth Resources Open File Report |date=1987 |volume=87-15 |url=https://www.dnr.wa.gov/Publications/ger_ofr87-15_goldendale_39k.pdf |archive-url=https://web.archive.org/web/20091220013300/http://www.dnr.wa.gov/Publications/ger_ofr87-15_goldendale_39k.pdf |archive-date=2009-12-20 |url-status=live |access-date=13 August 2020}}</ref> Because of the low potassium content of most basalts, weathering converts the basalt to calcium-rich [[clay]] ([[montmorillonite]]) rather than potassium-rich clay ([[illite]]). Further weathering, particularly in tropical climates, converts the montmorillonite to [[kaolinite]] or [[gibbsite]]. This produces the distinctive tropical [[soil]] known as [[laterite]].{{sfn|Blatt|Middleton|Murray|1980|pp=254–257}} The ultimate weathering product is [[bauxite]], the principal ore of aluminium.{{sfn|Blatt|Middleton|Murray|1980|pp=263–264}}

Chemical weathering also releases readily water-soluble cations such as [[calcium]], [[sodium]] and [[magnesium]], which give basaltic areas a strong [[buffer capacity]] against [[Soil acidification|acidification]].<ref name="gillman-etal-2002">{{cite journal |last1=Gillman |first1=G. P. |last2=Burkett |first2=D. C. |last3=Coventry |first3=R. J. |title=Amending highly weathered soils with finely ground basalt rock |journal=Applied Geochemistry |date=August 2002 |volume=17 |issue=8 |pages=987–1001 |doi=10.1016/S0883-2927(02)00078-1|bibcode=2002ApGC...17..987G }}</ref> Calcium released by basalts binds [[carbon dioxide|CO<sub>2</sub>]] from the atmosphere forming [[Calcium carbonate|CaCO<sub>3</sub>]] acting thus as a CO<sub>2</sub> trap.<ref name="mcgrail-etal-2006">{{cite journal |last1=McGrail |first1=B. Peter |last2=Schaef |first2=H. Todd |last3=Ho |first3=Anita M. |last4=Chien |first4=Yi-Ju |last5=Dooley |first5=James J. |last6=Davidson |first6=Casie L. |title=Potential for carbon dioxide sequestration in flood basalts: Sequestration in flood basalts |journal=Journal of Geophysical Research: Solid Earth |date=December 2006 |volume=111 |issue=B12 |pages=n/a |doi=10.1029/2005JB004169|doi-access=free }}</ref>

=== Metamorphism ===
[[File:Archean Greenstone Pillow Lava in Michigan USA 3.jpg|thumb|Metamorphosed basalt from an [[Archean]] [[greenstone belt]] in Michigan, US. The minerals that gave the original basalt its black colour have been metamorphosed into green minerals.]]

Intense heat or great pressure transforms basalt into its [[metamorphic rock]] equivalents. Depending on the temperature and pressure of metamorphism, these may include [[greenschist]], [[amphibolite]], or [[eclogite]]. Basalts are important rocks within metamorphic regions because they can provide vital information on the conditions of [[metamorphism]] that have affected the region.{{sfn|Blatt|Tracy|1996|loc=chapter 22}}

Metamorphosed basalts are important hosts for a variety of [[hydrothermal]] [[ore]]s, including deposits of gold, copper and [[volcanogenic massive sulfide ore deposit|volcanogenic massive sulfide]]s.<ref>{{Cite journal|last1=Yardley|first1=Bruce W. D.|last2=Cleverley|first2=James S.|date=2015|title=The role of metamorphic fluids in the formation of ore deposits|journal=Geological Society, London, Special Publications|language=en|volume=393|issue=1|pages=117–134|doi=10.1144/SP393.5|bibcode=2015GSLSP.393..117Y|s2cid=130626915|issn=0305-8719|doi-access=free}}</ref>

== Life on basaltic rocks ==
The common corrosion features of underwater volcanic basalt suggest that microbial activity may play a significant role in the chemical exchange between basaltic rocks and seawater. The significant amounts of reduced iron, Fe(II), and manganese, Mn(II), present in basaltic rocks provide potential energy sources for [[bacteria]]. Some Fe(II)-oxidizing bacteria cultured from iron-sulfide surfaces are also able to grow with basaltic rock as a source of Fe(II).<ref>{{cite journal|first1=Katrina J. |last1=Edwards |first2=Wolfgang |last2=Bach |first3=Daniel R. |last3=Rogers |title=Geomicrobiology of the Ocean Crust: A Role for Chemoautotrophic Fe-Bacteria |journal=Biological Bulletin |volume=204 |issue=2 |pages=180–185 |date=April 2003 |doi=10.2307/1543555 |pmid=12700150 |jstor=1543555 |s2cid=1717188 |url=https://www.biodiversitylibrary.org/part/9233 }}</ref> Fe- and Mn- oxidizing bacteria have been cultured from weathered submarine basalts of [[Kamaʻehuakanaloa Seamount]] (formerly Loihi).<ref>{{cite journal|last1=Templeton|first1=Alexis S.|last2=Staudigel|first2=Hubert|last3=Tebo|first3=Bradley M.|title=Diverse Mn(II)-Oxidizing Bacteria Isolated from Submarine Basalts at Loihi Seamount|journal=Geomicrobiology Journal|date=April 2005|volume=22|issue=3–4|pages=127–139|doi=10.1080/01490450590945951|bibcode=2005GmbJ...22..127T |s2cid=17410610}}</ref> The impact of bacteria on altering the chemical composition of basaltic glass (and thus, the [[oceanic crust]]) and seawater suggest that these interactions may lead to an application of [[hydrothermal vents]] to the [[origin of life]].<ref name="martin-etal-2008">{{cite journal |last1=Martin |first1=William |last2=Baross |first2=John |last3=Kelley |first3=Deborah |last4=Russell |first4=Michael J. |title=Hydrothermal vents and the origin of life |journal=Nature Reviews Microbiology |date=November 2008 |volume=6 |issue=11 |pages=805–814 |doi=10.1038/nrmicro1991|pmid=18820700 |bibcode=2008NRvM....6..805M |s2cid=1709272 }}</ref>

== Uses ==

[[File:P1050763 Louvre code Hammurabi face rwk.JPG|thumb|The [[Code of Hammurabi]] was engraved on a {{height|m=2.25}} tall basalt [[stele]] in around 1750 BC.]]

Basalt is used in construction (e.g. as building blocks or in the [[Foundation (engineering)|groundwork]]),<ref>{{cite journal |last1=Raj |first1=Smriti |last2=Kumar |first2=V Ramesh |last3=Kumar |first3=B H Bharath |last4=Iyer |first4=Nagesh R |title=Basalt: structural insight as a construction material |journal=Sādhanā |date=January 2017 |volume=42 |issue=1 |pages=75–84 |doi=10.1007/s12046-016-0573-9|doi-access=free }}</ref> making [[cobblestone]]s (from columnar basalt)<ref>{{cite journal |last1=Yıldırım |first1=Mücahit |title=Shading in the outdoor environments of climate-friendly hot and dry historical streets: The passageways of Sanliurfa, Turkey |journal=Environmental Impact Assessment Review |date=January 2020 |volume=80 |article-number=106318 |doi=10.1016/j.eiar.2019.106318|doi-access=free |bibcode=2020EIARv..8006318Y }}</ref> and in making [[statue]]s.<ref>{{cite journal |last1=Aldred |first1=Cyril |title=A Statue of King Neferkarē c Ramesses IX |journal=The Journal of Egyptian Archaeology |date=December 1955 |volume=41 |issue=1 |pages=3–8 |doi=10.1177/030751335504100102|s2cid=192232554 }}</ref><ref>{{cite journal |last1=Roobaert |first1=Arlette |title=A Neo-Assyrian Statue from Til Barsib |journal=Iraq |date=1996 |volume=58 |pages=79–87 |doi=10.2307/4200420|jstor=4200420 }}</ref> Heating and [[Extrusion|extruding]] basalt yields [[stone wool]], which has potential to be an excellent [[thermal insulation|thermal insulator]].<ref>{{cite web |url=http://basalt.pro/activities/materials/|title=Research surveys for basalt rock quarries |website=Basalt Projects }}</ref><ref>{{cite web |last1=De Fazio |first1=Piero |title=Basalt fiber: from earth an ancient material for innovative and modern application |url=http://www.enea.it/it/seguici/pubblicazioni/EAI/anno-2011/indice-world-view-3-2011/basalt-fiber-from-earth-an-ancient-material-for-innovative-and-modern-application |website=Italian national agency for new technologies, energy and sustainable economic development |access-date=17 December 2018 |language=en, it |archive-date=17 May 2019 |archive-url=https://web.archive.org/web/20190517081412/http://www.enea.it/it/seguici/pubblicazioni/EAI/anno-2011/indice-world-view-3-2011/basalt-fiber-from-earth-an-ancient-material-for-innovative-and-modern-application/ |url-status=dead }}</ref><ref>{{Cite web|url=http://www.ptonline.com/articles/composites-higher-properties-lower-cost|title=Composites: Higher Properties, Lower Cost|last=Schut|first=Jan H.|website=www.ptonline.com|date=August 2008 |access-date=2017-12-10}}</ref><ref>{{Cite web|url=http://www.compositesworld.com/articles/basalt-fibers-alternative-to-glass|title=Basalt Fibers: Alternative To Glass?|last=Ross|first=Anne|website=www.compositesworld.com|date=August 2006 |access-date=2017-12-10}}</ref>

[[Carbon sequestration]] in basalt has been studied as a means of removing carbon dioxide, produced by human industrialization, from the atmosphere. Underwater basalt deposits, scattered in seas around the globe, have the added benefit of the water serving as a barrier to the re-release of CO<sub>2</sub> into the atmosphere.<ref>{{cite news|last1=Hance|first1=Jeremy|title=Underwater rocks could be used for massive carbon storage on America's East Coast|url=http://news.mongabay.com/2010/0104-hance_ccs.html|access-date=4 November 2015|publisher=Mongabay|date=5 January 2010}}</ref><ref>{{cite journal |last1=Goldberg |first1=D. S. |last2=Takahashi |first2=T. |last3=Slagle |first3=A. L. |title=Carbon dioxide sequestration in deep-sea basalt |journal=Proceedings of the National Academy of Sciences |date=22 July 2008 |volume=105 |issue=29 |pages=9920–9925 |doi=10.1073/pnas.0804397105|pmid=18626013 |pmc=2464617 |bibcode=2008PNAS..105.9920G |doi-access=free }}</ref>

== See also ==
* {{annotated link|Basalt fan structure}}
* {{annotated link|Basalt fiber}}
* {{annotated link|Bimodal volcanism}}
* {{annotated link|Plutonism}}
* {{annotated link|Polybaric melting}}
* {{annotated link|Shield volcano}}
* {{annotated link|Spilite}}
* {{annotated link|Sideromelane}}
* {{annotated link|Volcano}}
* {{portal-inline|Geology}}

== References ==
{{reflist}}

==Sources==
*{{cite book |last1=Blatt |first1=Harvey |last2=Tracy |first2=Robert J. |title=Petrology: igneous, sedimentary, and metamorphic |date=1996 |publisher=W.H. Freeman |location=New York |isbn=978-0-7167-2438-4 |edition=2nd }}
*{{cite book |last1=Blatt |first1=Harvey |last2=Middleton |first2=Gerard |last3=Murray |first3=Raymond |title=Origin of sedimentary rocks |date=1980 |publisher=Prentice-Hall |location=Englewood Cliffs, N.J. |isbn=978-0-13-642710-0 |edition=2d }}
*{{cite book |last1=Crawford |first1=A.J. |title=Boninites |date=1989 |publisher=Unwin Hyman |location=London |isbn=978-0-04-445003-0 }}
*{{cite book |last1=Hyndman |first1=Donald W. | title=Petrology of igneous and metamorphic rocks |edition=2nd |year=1985 |publisher=McGraw-Hill |isbn=978-0-07-031658-4 }}
*{{cite book |last1=Klein |first1=Cornelis |last2=Hurlbut |first2=Cornelius S. Jr. |title=Manual of mineralogy : (after James D. Dana) |date=1993 |publisher=Wiley |location=New York |isbn=978-0-471-57452-1 |edition=21st }}
*{{cite book |last1=Levin |first1=Harold L. |title=The earth through time |date=2010 |publisher=J. Wiley |location=Hoboken, N.J. |isbn=978-0-470-38774-0 |edition=9th }}
*{{cite book |last1=Lillie |first1=Robert J. |title=Parks and plates : the geology of our national parks, monuments, and seashores |date=2005 |publisher=W.W. Norton |location=New York |isbn=978-0-393-92407-7 |edition=1st }}
*{{cite book |last1=Macdonald |first1=Gordon A. |last2=Abbott |first2=Agatin T. |last3=Peterson |first3=Frank L. |title=Volcanoes in the sea : the geology of Hawaii |date=1983 |publisher=University of Hawaii Press |location=Honolulu |isbn=978-0-8248-0832-7 |edition=2nd }}
*{{cite book |last1=McBirney |first1=Alexander R. |title=Igneous petrology |date=1984 |publisher=Freeman, Cooper |location=San Francisco, Calif. |isbn=978-0-19-857810-9 }}
*{{cite book |last1=Parfitt |first1=Elisabeth Ann |last2=Parfitt |first2=Liz |last3=Wilson |first3=Lionel |title=Fundamentals of Physical Volcanology |date=2008 |publisher=Wiley |isbn=978-0-632-05443-5 }}
*{{cite book |last1=Philpotts |first1=Anthony R. |last2=Ague |first2=Jay J. |title=Principles of igneous and metamorphic petrology |date=2009 |publisher=Cambridge University Press |location=Cambridge, UK |isbn=978-0-521-88006-0 |edition=2nd }}
*{{cite book |last1=Schmincke |first1=Hans-Ulrich |title=Volcanism |date=2003 |publisher=Springer |location=Berlin |isbn=978-3-540-43650-8 }}

==Further reading==
{{Refbegin}}
*{{cite book |last1=Francis |first1=Peter |last2=Oppenheimer |first2=Clive |title=Volcanoes |date=2003 |publisher=Oxford University Press |location=Oxford |isbn=978-0-19-925469-9 |edition=2nd |ref=none}}
*{{cite book |last1=Gill |first1=Robin |title=Igneous rocks and processes: a practical guide |url=https://archive.org/details/Igneous_Rocks_and_Processes_A_Practical_Guide_by_R_Gill |date=2010 |publisher=Wiley-Blackwell |location=Chichester, West Sussex, UK |isbn=978-1-4443-3065-6 |ref=none}}
*{{cite book |last1=Hall |first1=Anthony |title=Igneous petrology |date=1996 |publisher=Longman Scientific & Technical |location=Harlow |isbn=978-0-582-23080-4 |ref=none}}
*{{cite book |editor-last1=Siegesmund |editor-first1=Siegfried |editor-last2=Snethlage |editor-first2=Rolf |title=Stone in architecture properties, durability |date=2013 |publisher=Springer Science & Business Media |isbn=978-3-662-10070-7 |edition=3rd |ref=none}}
*{{cite book |last1=Young |first1=Davis A. |title=Mind over magma : the story of igneous petrology |date=2003 |publisher=Princeton University Press |location=Princeton, N.J. |isbn=978-0-691-10279-5 |ref=none}}
{{Refend}}

== External links ==
{{Commons category|Basalt}}
{{Wikisource1911Enc|Basalt}}
* [https://web.archive.org/web/20071107063242/http://giantcrystals.strahlen.org/europe/basalt.htm Basalt Columns]
* [http://geographyinaction.co.uk//Geology%20files/Basalt.html Basalt in Northern Ireland] {{Webarchive|url=https://web.archive.org/web/20210224191248/http://geographyinaction.co.uk//Geology%20files/Basalt.html |date=24 February 2021 }}
* [https://web.archive.org/web/20070913025149/http://www.geology.sdsu.edu/how_volcanoes_work/lava_water.html Lava–water interface]
* [https://web.archive.org/web/20080820010048/http://www.petdb.org/ PetDB, the Petrological Database]
* [https://web.archive.org/web/20080607121825/http://www.union.edu/PUBLIC/GEODEPT/COURSES/petrology/moon_rocks/ Petrology of Lunar Rocks and Mare Basalts]
* [https://web.archive.org/web/20080916123604/http://volcanoes.usgs.gov/images/pglossary/PillowLava.php Pillow lava USGS]

{{Igneous rocks}}
{{basalt}}
{{Rock type}}
{{Volcanoes}}

{{Authority control}}

[[Category:Basalt| ]]