# Lava

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{{Short description|Molten rock expelled by a volcano during an eruption}}
{{Redirect|Lava flow|the programming anti-pattern|Lava flow (programming)|other uses|Lava (disambiguation)}}
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{{Use British English|date=January 2022}}

[[File:001 Volcano eruption of Litli-Hrútur in Iceland in 2023 Photo by Giles Laurent.jpg|thumb|upright=1.5|Fresh lava from [Fagradalsfjall](/source/Fagradalsfjall) volcano eruption in Iceland, 2023]]
'''Lava''' is molten or partially molten rock ([magma](/source/magma)) that has been expelled from the interior of a [terrestrial planet](/source/terrestrial_planet) (such as [Earth](/source/Earth)) or a [moon](/source/Natural_satellite) onto its surface. Lava may be erupted at a [volcano](/source/volcano) or through a [fracture](/source/Fissure_vent) in the [crust](/source/Crust_(geology)), on land or underwater, usually at temperatures from {{convert|800|to|1200|C|F}}. Lava may be erupted directly onto the land surface or onto the [sea floor](/source/sea_floor) or it may be ejected into the atmosphere before falling back down. The solid [volcanic rock](/source/volcanic_rock) resulting from subsequent cooling of the molten material is often also called ''lava''. 

A '''lava flow''' is an outpouring of lava during an [effusive eruption](/source/effusive_eruption). (An [explosive eruption](/source/explosive_eruption), by contrast, produces a mixture of [volcanic ash](/source/volcanic_ash) and other fragments called [tephra](/source/tephra), not lava flows.) The [viscosity](/source/viscosity) of most molten lava is about that of [ketchup](/source/ketchup), roughly 10,000 to 100,000 times that of water (the latter two substances measured at {{cvt|25|C}} and 1 [atm](/source/Standard_atmosphere_(unit))). Even so, lava can flow great distances before cooling causes it to solidify, because lava exposed to air quickly develops a solid crust that insulates the remaining liquid lava, helping to keep it hot and inviscid enough to continue flowing.<ref>{{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 |pages=53–55 |edition=2nd}}</ref>

== Etymology ==
The word ''lava'' comes from [Italian](/source/Italian_language) and is probably derived from the [Latin](/source/Latin) word {{lang|la|labes}}, which means a {{gloss|fall}} or {{gloss|slide}}.<ref>{{cite web|url=http://www.m-w.com/dictionary/lava |title=Lava |work=Merriam-Webster Online Dictionary |date=2012-08-31 |access-date=8 December 2013}}</ref><ref>{{cite web|url=http://dictionary.reference.com/browse/lava |title=Lava |publisher=Dictionary.reference.com |date=1994-12-07 |access-date=8 December 2013}}</ref> An early use of the word in connection with extrusion of magma from below the surface is found in a short account of the 1737 eruption of [Vesuvius](/source/Vesuvius), written by [Francesco Serao](/source/Francesco_Serao), who described "a flow of fiery lava" as an analogy to the flow of water and mud down the flanks of the volcano (a [lahar](/source/lahar)) after heavy [rain](/source/rain).<ref>{{cite book |last1=Serao |first1=Francesco |title=Istoria dell' incendio del Vesuvio accaduto nel mese di maggio dell'anno MDCCXXXVII |date=1778 |publisher=Presso Il De Bonis |location=Naples |url=https://archive.org/details/istoriadellincen00sera/page/n3/mode/2up |access-date=6 August 2022}}</ref><ref>{{cite web |title=Vesuvius Erupts, 1738 |url=https://vulcan.lindahall.org/9.shtml |website=Linda Hall Library of Science, Engineering & Technology |access-date=6 August 2022}}</ref>

== Properties==
=== Composition ===
thumb|Video of lava agitating and bubbling in the volcano eruption of Litli-Hrútur, 2023
Solidified lava on the [Earth's crust](/source/Earth's_crust) is predominantly [silicate minerals](/source/silicate_minerals): mostly [feldspar](/source/feldspar)s, [feldspathoid](/source/feldspathoid)s, [olivine](/source/olivine), [pyroxene](/source/pyroxene)s, [amphibole](/source/amphibole)s, [mica](/source/mica)s and [quartz](/source/quartz).{{sfn|Philpotts|Ague|2009|p=19}} Rare nonsilicate lavas can be formed by local melting of nonsilicate mineral deposits<ref name="ChileIronOxideLava">{{cite journal | url=https://www.researchgate.net/publication/241044499 | title=Geological, Geographical and Legal Considerations for the Conservation of Unique Iron Oxide and Sulphur Flows at El Laco and Lastarria Volcanic Complexes, Central Andes, Northern Chile | author=Guijón, R. |author2=Henríquez, F. |author3=Naranjo, J.A. | journal=Geoheritage | year=2011 | volume=3 | issue=4 | pages=99–315 | doi=10.1007/s12371-011-0045-x| bibcode=2011Geohe...3..299G | s2cid=129179725 }}</ref> or by separation of a magma into [immiscible](/source/immiscible) silicate and nonsilicate liquid [phases](/source/State_of_matter).<ref name="IronOxidelava">{{cite journal | url=https://www.researchgate.net/publication/235632335 | title=Apatite–monazite relations in the Kiirunavaara magnetite–apatite ore, northern Sweden | author=Harlov, D.E. | journal=Chemical Geology | year=2002 | volume=191 | issue=1–3 | pages=47–72 | doi=10.1016/s0009-2541(02)00148-1| bibcode=2002ChGeo.191...47H |display-authors=etal}}</ref>

==== Silicate ====
Silicate lavas are molten mixtures dominated by [oxygen](/source/oxygen) and [silicon](/source/silicon), the [most abundant elements of the Earth's crust](/source/Abundance_of_elements_in_Earth's_crust), with smaller quantities of [aluminium](/source/aluminium), [calcium](/source/calcium), [magnesium](/source/magnesium), [iron](/source/iron), [sodium](/source/sodium), and [potassium](/source/potassium) and minor amounts of many other elements.{{sfn|Philpotts|Ague|2009|p=19}} [Petrologist](/source/Petrologist)s routinely express the composition of a silicate lava in terms of the weight or [molar mass](/source/molar_mass) fraction of the oxides of the major elements (other than oxygen) present in the lava.{{sfn|Philpotts|Ague|2009|pp=132-133}}

The silica component dominates the physical behavior of silicate magmas. Silicon ions in lava strongly bind to four oxygen ions in a tetrahedral arrangement. If an oxygen ion is bound to two silicon ions in the melt, it is described as a bridging oxygen, and lava with many clumps or chains of silicon ions connected by bridging oxygen ions is described as partially polymerized. Aluminium in combination with alkali metal oxides (sodium and potassium) also tends to polymerize the lava.{{sfn|Philpotts|Ague|2009|p=25}} Other [cations](/source/Ion), such as ferrous iron, calcium, and magnesium, bond much more weakly to oxygen and reduce the tendency to polymerize.<ref>{{cite book |last1=Schmincke |first1=Hans-Ulrich |title=Volcanism |date=2003 |publisher=Springer |location=Berlin |isbn=978-3-540-43650-8 |page=38}}</ref> Partial polymerization makes the lava viscous, so lava high in silica is much more viscous than lava low in silica.{{sfn|Philpotts|Ague|2009|p=25}}

Because of the role of silica in determining viscosity and because many other properties of a lava (such as its temperature) are observed to correlate with silica content, silicate lavas are divided into four chemical types based on silica content: ''felsic'', ''intermediate'', ''mafic'', and ''ultramafic''.<ref>{{cite book |last1=Casq |first1=R.A.F. |url=https://archive.org/details/volcanicsuccessi0000casr/page/528/mode/2up |title=Volcanic Successions |last2=Wright |first2=J.V. |date=1987 |publisher=Unwin Hyman Inc |isbn=978-0-04-552022-0 |page=528 |url-access=registration}}</ref>

===== Felsic =====
''Felsic'' or [silicic](/source/Silicon_dioxide) lavas have a silica content greater than 63%. They include [rhyolite](/source/rhyolite) and [dacite](/source/dacite) lavas. With such a high silica content, these lavas are extremely viscous, ranging from 10<sup>8</sup> [cP](/source/centipoise) (10<sup>5</sup> Pa⋅s) for hot rhyolite lava at {{cvt|1200|C||}} to 10<sup>11</sup> cP (10<sup>8</sup> Pa⋅s) for cool rhyolite lava at {{cvt|800|C||}}.{{sfn|Philpotts|Ague|2009|p=23}} For comparison, water has a viscosity of about 1 cP (0.001 Pa⋅s). Because of this very high viscosity, felsic lavas usually erupt explosively to produce [pyroclastic](/source/Pyroclastic_rock) (fragmental) deposits. However, rhyolite lavas occasionally erupt effusively to form [lava spine](/source/lava_spine)s, [lava dome](/source/lava_dome)s or "coulees" (which are thick, short lava flows).{{sfn|Philpotts|Ague|2009|pp=70-77}}  The lavas typically fragment as they extrude, producing block lava flows. These often contain [obsidian](/source/obsidian).{{sfn|Schmincke|2003|p=132}}

Felsic magmas can erupt at temperatures as low as {{convert|800|°C}}.{{sfn|Philpotts|Ague|2009|p=20}} Unusually hot (>950 °C; >1,740 °F) rhyolite lavas, however, may flow for distances of many tens of kilometres, such as in the [Snake River Plain](/source/Snake_River_Plain) of the northwestern United States.<ref>{{cite book |last1=Bonnichsen |first1=B. |last2=Kauffman, D.F. |title=The Emplacement of Silicic Domes and Lava Flows |year=1987 |chapter=Physical features of rhyolite lava flows in the Snake River Plain volcanic province, southwestern Idaho |publisher=Geological Society of America |series=Geological Society of America Special Papers |volume=212 |pages=119–145|doi=10.1130/SPE212-p119 |isbn=0-8137-2212-8 }}</ref><!-- Rather an old source; are the Snake River flows still regarded as fluid flows and not ash flows?-->

===== Intermediate =====
''Intermediate'' or [andesitic](/source/Andesite) lavas contain 52% to 63% silica, and are lower in aluminium and usually somewhat richer in [magnesium](/source/magnesium) and [iron](/source/iron) than felsic lavas. Intermediate lavas form andesite domes and block lavas and may occur on steep [composite volcano](/source/composite_volcano)es, such as in the [Andes](/source/Andes).{{sfn|Schmincke|2003|pp=21-24,132,143}} They are also commonly hotter than felsic lavas, in the range of {{convert|850|to|1100|°C}}. Because of their lower silica content and higher eruptive temperatures, they tend to be much less viscous, with a typical viscosity of 3.5 million cP (3,500 Pa⋅s) at {{cvt|1200|C||}}. This is slightly greater than the viscosity of smooth [peanut butter](/source/peanut_butter).{{sfn|Philpotts|Ague|2009|pp=23-611}} Intermediate lavas show a greater tendency to form [phenocrysts](/source/phenocrysts).<ref>{{cite journal |last1=Takeuchi |first1=Shingo |title=Preeruptive magma viscosity: An important measure of magma eruptibility |journal=Journal of Geophysical Research |date=5 October 2011 |volume=116 |issue=B10|article-number=B10201 |doi=10.1029/2011JB008243| bibcode=2011JGRB..11610201T |doi-access=free }}</ref> Higher iron and magnesium tends to manifest as a darker [groundmass](/source/groundmass), including amphibole or pyroxene phenocrysts.{{sfn|Philpotts|Ague|2009|pp=1376-377}}

===== Mafic =====
''Mafic'' or [basaltic](/source/basaltic) lavas are typified by relatively high magnesium oxide and iron oxide content (whose molecular formulas provide the consonants in mafic) and have a silica content limited to a range of 52% to 45%. They generally erupt at temperatures of {{convert|1100 to 1200|°C}} and at relatively low viscosities, around 10<sup>4</sup> to 10<sup>5</sup> cP (10 to 100 Pa⋅s). This is similar to the viscosity of [ketchup](/source/ketchup),{{sfn|Philpotts|Ague|2009|pp=23-25}} although it is still many orders of magnitude higher than that of water.  Mafic lavas tend to produce low-profile [shield volcano](/source/shield_volcano)es or [flood basalt](/source/flood_basalt)s, because the less viscous lava can flow for long distances from the vent. The thickness of a solidified basaltic lava flow, particularly on a low slope, may be much greater than the thickness of the moving molten lava flow at any one time, because basaltic lavas may "inflate" by a continued supply of lava and its pressure on a solidified crust.{{sfn|Philpotts|Ague|2009|p=53–55, 59–64}} Most basaltic lavas are of {{okina}}a{{okina}}ā or pāhoehoe types, rather than block lavas. Underwater, they can form [pillow lavas](/source/pillow_lavas), which are rather similar to entrail-type pahoehoe lavas on land.{{sfn|Schmincke|2003|pp=128-132}}

===== Ultramafic =====
''Ultramafic'' lavas, such as [komatiite](/source/komatiite) and highly magnesian magmas that form [boninite](/source/boninite), take the composition and temperatures of eruptions to the extreme. All have a silica content under 45%. Komatiites contain over 18% magnesium oxide and are thought to have erupted at temperatures of {{convert|1600|°C}}. At this temperature there is practically no polymerization of the mineral compounds, creating a highly mobile liquid.<ref name="Condie1994">{{cite book | title=Archean Crustal Evolution | publisher=Elsevier | location=Amsterdam | editor=Condie, K.C.| year=1994 | chapter=Archean komatiites | author=Arndt, N.T. | page=19 | isbn=978-0-444-81621-4}}</ref> Viscosities of komatiite magmas are thought to have been as low as 100 to 1000 cP (0.1 to 1 Pa⋅s), similar to that of light motor oil.{{sfn|Philpotts|Ague|2009|p=23}} Most ultramafic lavas are no younger than the [Proterozoic](/source/Proterozoic), with a few ultramafic magmas known from the [Phanerozoic](/source/Phanerozoic) in Central America that are attributed to a hot [mantle plume](/source/mantle_plume). No modern komatiite lavas are known, as the [Earth's mantle](/source/Earth's_mantle) has cooled too much to produce highly magnesian magmas.{{sfn|Philpotts|Ague|2009|pp=399-400}}

===== Alkaline =====
Some silicate lavas have an elevated content of [alkali metal oxide](/source/alkali_metal_oxide)s (sodium and potassium), particularly in regions of [continental rifting](/source/continental_rifting), areas overlying deeply [subducted](/source/subduction) [plates](/source/Tectonic_plate), or at intraplate [hotspots](/source/Hotspot_(geology)).{{sfn|Philpotts|Ague|2009|pp=139-148}} Their silica content can range from ultramafic ([nephelinite](/source/nephelinite)s, [basanite](/source/basanite)s and [tephrite](/source/tephrite)s) to felsic ([trachyte](/source/trachyte)s). They are more likely to be generated at greater depths in the mantle than subalkaline magmas.{{sfn|Philpotts|Ague|2009|pp=606-607}} Olivine [nephelinite](/source/nephelinite) lavas are both ultramafic and highly alkaline, and are thought to have come from much deeper in the [mantle](/source/mantle_(geology)) of the [Earth](/source/Earth) than other lavas.<ref>{{cite web| url=http://gsc.nrcan.gc.ca/volcanoes/cat/feature_volcano_e.php |work=Catalogue of Canadian volcanoes| title=Stikine Volcanic Belt: Volcano Mountain|archive-url=https://web.archive.org/web/20090307140121/http://gsc.nrcan.gc.ca/volcanoes/cat/feature_volcano_e.php |archive-date=2009-03-07|access-date=23 November 2007}}</ref>
{| style="border:0px solid black;"
|+
!valign="top" |
{| class="wikitable" style="text-align: left;"
|+Examples of lava compositions (wt%){{sfn|Philpotts|Ague|2009|p=145}}
! Component
! [Nephelinite](/source/Nephelinite)
! [Tholeiitic](/source/Tholeiitic) [picrite](/source/picrite)
! [Tholeiitic basalt](/source/Tholeiitic_basalt)
! [Andesite](/source/Andesite)
! [Rhyolite](/source/Rhyolite)
|-
| Silica |[SiO<sub>2</sub>](/source/SiO2)
| 39.7
| 46.4
| 53.8
| 60.0
| 73.2
|-
| [TiO<sub>2</sub>](/source/TiO2)
| 2.8
| 2.0
| 2.0
| 1.0
| 0.2
|-
| [Al<sub>2</sub>O<sub>3</sub>](/source/Al2O3)
| 11.4
| 8.5
| 13.9
| 16.0
| 14.0
|- 
| [Fe<sub>2</sub>O<sub>3</sub>](/source/Fe2O3)
| 5.3
| 2.5
| 2.6
| 1.9
| 0.6
|- 
| [FeO](/source/FeO)
| 8.2
| 9.8
| 9.3
| 6.2
| 1.7
|- 
| [MnO](/source/MnO)
| 0.2
| 0.2
| 0.2
| 0.2
| 0.0
|- 
| [MgO](/source/MgO)
| 12.1
| 20.8
| 4.1
| 3.9
| 0.4
|- 
| [CaO](/source/CaO)
| 12.8
| 7.4
| 7.9
| 5.9
| 1.3
|- 
| [Na<sub>2</sub>O](/source/Na2O)
| 3.8
| 1.6
| 3.0
| 3.9
| 3.9
|-
| [K<sub>2</sub>O](/source/K2O)
| 1.2
| 0.3
| 1.5
| 0.9
| 4.1
|-
| [P<sub>2</sub>O<sub>5</sub>](/source/P2O5)
| 0.9
| 0.2
| 0.4
| 0.2
| 0.0
|}
! valign="top" | {{Pie chart
| radius = 100
| thumb = 
| caption = Tholeiitic basalt lava
| other = 
| label1 = SiO<sub>2</sub> 
| value1 = 53.8
| label2 = Al<sub>2</sub>O<sub>3</sub>
| value2 =13.9
| label3 =FeO
| value3 =9.3
| label4 =CaO
| value4 =7.9
| label5 =MgO
| value5 =4.1
| label6 =Na<sub>2</sub>O
| value6 =3.0
| label7 = Fe<sub>2</sub>O<sub>3</sub>
| value7=2.6
| label8 = TiO<sub>2</sub>
| value8=2.0
| label9 = K<sub>2</sub>O
| value9 = 1.5
| label10 = P<sub>2</sub>O<sub>5</sub>
| value10 = 0.4
| label11 = MnO
| value11 = 0.2
}}
! valign="top" |{{Pie chart
| radius = 100
| thumb = 
| caption = Rhyolite lava
| other = 
| label1 = SiO<sub>2</sub> 
| value1 = 73.2
| label2 = Al<sub>2</sub>O<sub>3</sub>
| value2 = 14
| label9 =K<sub>2</sub>O
| value9 = 4.1
| label6 =Na<sub>2</sub>O
| value6 = 3.9
| label3 =FeO
| value3 = 1.7
| label4 = CaO
| value4 = 1.3
| label7 = Fe<sub>2</sub>O<sub>3</sub>
| value7= 0.6
| label5 = MgO
| value5= 0.4
| label8 = TiO<sub>2</sub>
| value8 = 0.2
| label10 = P<sub>2</sub>O<sub>5</sub>
| value10 = 0.
| label11 = MnO
| value11 = 0.
}}
|}

==== Non-silicate ====
Some lavas of unusual composition have erupted onto the surface of the Earth. These include:
* [Carbonatite](/source/Carbonatite) and [natrocarbonatite](/source/natrocarbonatite) lavas are known from [Ol Doinyo Lengai](/source/Ol_Doinyo_Lengai) volcano in [Tanzania](/source/Tanzania), which is the sole example of an active carbonatite volcano.<ref>[http://www.geology.sdsu.edu/how_volcanoes_work/Unusual%20lava.html Vic Camp, ''How volcanoes work'', Unusual Lava Types] {{Webarchive|url=https://web.archive.org/web/20171023185741/http://www.geology.sdsu.edu/how_volcanoes_work/Unusual%20lava.html |date=2017-10-23 }}, [San Diego State University](/source/San_Diego_State_University), Geology</ref> Carbonatites in the geologic record are typically 75% carbonate minerals, with lesser amounts of silica-undersaturated silicate minerals (such as [mica](/source/mica)s and olivine), [apatite](/source/apatite), [magnetite](/source/magnetite), and [pyrochlore](/source/pyrochlore). This may not reflect the original composition of the lava, which may have included [sodium carbonate](/source/sodium_carbonate) that was subsequently removed by hydrothermal activity, though laboratory experiments show that a calcite-rich magma is possible. Carbonatite lavas show [stable isotope ratio](/source/stable_isotope_ratio)s indicating they are derived from the highly alkaline silicic lavas with which they are always associated, probably by separation of an immiscible phase.{{sfn|Philpotts|Ague|2009|pp=396-397}} Natrocarbonatite lavas of Ol Doinyo Lengai are composed mostly of sodium carbonate, with about half as much calcium carbonate and half again as much potassium carbonate, and minor amounts of halides, fluorides, and sulphates. The lavas are extremely fluid, with viscosities only slightly greater than water, and are very cool, with measured temperatures of {{cvt|491|to|544|C}}.<ref>{{cite journal |last1=Keller |first1=Jörg |last2=Krafft |first2=Maurice |title=Effusive natrocarbonatite activity of Oldoinyo Lengai, June 1988 |journal=Bulletin of Volcanology |date=November 1990 |volume=52 |issue=8 |pages=629–645 |doi=10.1007/BF00301213|bibcode=1990BVol...52..629K |s2cid=129106033 }}</ref>
* [Iron oxide](/source/Iron_oxide) lavas are thought to be the source of the [iron ore](/source/iron_ore) at [Kiruna](/source/Kiruna), [Sweden](/source/Sweden) which formed during the [Proterozoic](/source/Proterozoic).<ref name="IronOxidelava"/> Iron oxide lavas of [Pliocene](/source/Pliocene) age occur at the [El Laco](/source/El_Laco_(volcano)) volcanic complex on the Chile-Argentina border.<ref name="ChileIronOxideLava"/> Iron oxide lavas are thought to be the result of [immiscible](/source/Miscibility) separation of iron oxide magma from a parental magma of [calc-alkaline](/source/Calc-alkaline_magma_series) or alkaline composition.<ref name="IronOxidelava"/> (Some geologists, however, interpret the El Laco iron oxide rocks as silicate lava flows that have been hydrothermally altered after their eruption).<ref>Mungall, J. E. ; Naslund, H. R. (2009) [https://ui.adsabs.harvard.edu/abs/2009AGUSM.V12A..04M/abstract "Melt inclusions in Fe oxide and phosphate tephra of El Laco volcano, Chile"], American Geophysical Union, Spring Meeting 2009, abstract id. V12A-04.</ref> 
* [Sulfur](/source/Sulfur) lava flows up to {{convert|250|m|0|abbr=off}} long and {{convert|10|m|0|abbr=off}} wide occur at [Lastarria](/source/Lastarria) volcano, Chile. They were formed by the melting of sulfur deposits at temperatures as low as {{convert|113|°C}}.<ref name="ChileIronOxideLava"/>

The term "lava" can also be used to refer to molten "ice mixtures" in eruptions on the icy [satellites](/source/Natural_satellite) of the [Solar System](/source/Solar_System)'s [giant planet](/source/giant_planet)s.<ref>{{cite book|editor-last1=McBride|editor-last2=Gilmore|year=2007|title=An introduction to the Solar System|publisher=[Cambridge University Press](/source/Cambridge_University_Press)|page=392}}</ref>

=== Rheology ===
[[Image:PahoehoeLava.jpg|thumb|upright|Toes of a pāhoehoe advance across a road in [Kalapana](/source/Kalapana%2C_Hawaii) on the east rift zone of [Kīlauea](/source/Kilauea) Volcano in [Hawaii, United States](/source/Hawaii)]]
The lava's viscosity mostly determines the behavior of lava flows. While the temperature of common silicate lava ranges from about {{cvt|800|C}} for felsic lavas to {{cvt|1200|C}} for mafic lavas,{{sfn|Philpotts|Ague|2009|p=20}} its viscosity ranges over seven orders of magnitude, from 10<sup>11</sup> cP (10<sup>8</sup> Pa⋅s) for felsic lavas to 10<sup>4</sup> cP (10 Pa⋅s) for mafic lavas.{{sfn|Philpotts|Ague|2009|p=20}} Lava viscosity is mostly determined by composition but also depends on temperature{{sfn|Philpotts|Ague|2009|p=23}} and shear rate.<ref name=Sonder>{{cite journal|last1=Sonder|first1=I|last2=Zimanowski|first2=B|last3=Büttner|first3=R|year=2006|title=Non-Newtonian viscosity of basaltic magma|journal=Geophysical Research Letters|volume=330|issue=2|pages=L02303|doi=10.1029/2005GL024240|bibcode=2006GeoRL..33.2303S|doi-access=free}}</ref>

Lava viscosity determines the [kind of volcanic activity](/source/Types_of_volcanic_eruptions) that takes place when the lava is erupted. The greater the viscosity, the greater the tendency for eruptions to be explosive rather than effusive. As a result, most lava flows on Earth, Mars, and Venus are composed of basalt lava.{{sfn|Schmincke|2003|p=128}} On Earth, 90% of lava flows are mafic or ultramafic, with intermediate lava making up 8% of flows and felsic lava making up just 2% of flows.<ref name="umass">{{cite web |title=Lava Flows |url=http://www.geo.umass.edu/courses/volcanology/Lava%20Flows.pdf |website=UMass Department of Geosciences |publisher=University of Massachusetts Amherst |access-date=5 June 2018 |page=19 |date=11 February 2004}}</ref> Viscosity also determines the aspect (thickness relative to lateral extent) of flows, the speed with which flows move, and the surface character of the flows.{{sfn|Philpotts|Ague|2009|p=23}}<ref name="PetersonTilling1980">{{cite journal |last1=Peterson |first1=Donald W. |last2=Tilling |first2=Robert I. |title=Transition of basaltic lava from pahoehoe to aa, Kilauea Volcano, Hawaii: Field observations and key factors |journal=Journal of Volcanology and Geothermal Research |date=May 1980 |volume=7 |issue=3–4 |pages=271–293 |doi=10.1016/0377-0273(80)90033-5|bibcode=1980JVGR....7..271P }}</ref>

When highly viscous lavas erupt effusively rather than in their more common explosive form, they almost always erupt as high-aspect flows or domes. These flows take the form of block lava rather than {{okina}}a{{okina}}ā or pāhoehoe. Obsidian flows are common.{{sfn|Schmincke|2003|pp=132-138}} Intermediate lavas tend to form steep stratovolcanoes, with alternating beds of lava from effusive eruptions and tephra from explosive eruptions.{{sfn|Schmincke|2003|pp=143-144}} Mafic lavas form relatively thin flows that can move great distances, forming shield volcanoes with gentle slopes.{{sfn|Schmincke|2003|pp=127-128}}

In addition to melted rock, most lavas contain solid crystals of various minerals, fragments of exotic rocks known as [xenolith](/source/xenolith)s, and fragments of previously solidified lava. The crystal content of most lavas gives them [thixotropic](/source/thixotropy) and [shear thinning](/source/shear_thinning) properties.<ref>{{cite journal |title=Transient phenomena in vesicular lava flows based on laboratory experiments with analogue materials |journal=Journal of Volcanology and Geothermal Research|volume=132 |issue=2–3 |pages=115–136 |doi=10.1016/s0377-0273(03)00341-x  |last1=Pinkerton |first1=H. |first2=N. |last2=Bagdassarov |year=2004 |bibcode=2004JVGR..132..115B}}</ref> In other words, most lavas do not behave like Newtonian fluids, in which the rate of flow is proportional to the [shear stress](/source/shear_stress). Instead, a typical lava is a [Bingham fluid](/source/Bingham_fluid), which shows considerable resistance to flow until a stress threshold, called the yield stress, is crossed.{{sfn|Schmincke|2003|pp=39-40}} This results in [plug flow](/source/plug_flow) of partially crystalline lava. A familiar example of plug flow is toothpaste squeezed out of a toothpaste tube. The toothpaste comes out as a semisolid plug, because shear is concentrated in a thin layer in the toothpaste next to the tube and only there does the toothpaste behave as a fluid. Thixotropic behavior also hinders crystals from settling out of the lava.{{sfn|Philpotts|Ague|2009|p=40}} Once the crystal content reaches about 60%, the lava ceases to behave like a fluid and begins to behave like a solid. Such a mixture of crystals with melted rock is sometimes described as ''crystal mush''.{{sfn|Philpotts|Ague|2009|p=16}}

Lava flow speeds vary based primarily on viscosity and slope.  In general, lava flows slowly, with typical speeds for Hawaiian basaltic flows of {{cvt|0.25|mph|sigfig=2|order=flip}} and maximum speeds of {{cvt|6|to|30|mph|0|order=flip}} on steep slopes.<ref name=umass/> An exceptional speed of {{cvt|20|to|60|mph|order=flip}} was recorded following the collapse of a lava lake at [Mount Nyiragongo](/source/Mount_Nyiragongo).<ref name=umass/> The scaling relationship for lavas is that the average speed of a flow scales as the square of its thickness divided by its viscosity.{{sfn|Philpotts|Ague|2009|p=71}} This implies that a rhyolite flow would have to be about a thousand times thicker than a basalt flow to flow at a similar speed.

===Temperature===
[[File:Giant's Causeway 2006 08.jpg|thumbnail|Columnar jointing in [Giant's Causeway](/source/Giant's_Causeway) in [Northern Ireland](/source/Northern_Ireland)]]
The temperature of most types of molten lava ranges from about {{cvt|800|C}} to {{cvt|1200|C}}{{Sfn|Philpotts|Ague|2009|p=20}} depending on the lava's chemical composition. This temperature range is similar to the hottest temperatures achievable with a forced air charcoal forge.<ref>{{cite journal |last1=Cheng |first1=Zhilong |last2=Yang |first2=Jian |last3=Zhou |first3=Lang |last4=Liu |first4=Yan |last5=Wang |first5=Qiuwang |title=Characteristics of charcoal combustion and its effects on iron-ore sintering performance |journal=Applied Energy |date=January 2016 |volume=161 |pages=364–374 |doi=10.1016/j.apenergy.2015.09.095|bibcode=2016ApEn..161..364C }}</ref> Lava is most fluid when first erupted, becoming much more viscous as its temperature drops.{{sfn|Philpotts|Ague|2009|p=23}}

Lava flows quickly develop an insulating crust of solid rock as a result of radiative loss of heat. Thereafter, the lava cools by a very slow conduction of heat through the rocky crust. For instance, geologists of the [United States Geological Survey](/source/United_States_Geological_Survey) regularly drilled into the Kilauea Iki lava lake, formed in an eruption in 1959. After three years, the solid surface crust, whose base was at a temperature of {{cvt|1065|C}}, was still only {{cvt|14|m}} thick, even though the lake was about {{cvt|100|m}} deep. Residual liquid was still present at depths of around {{cvt|80|m}} nineteen years after the eruption.{{sfn|Philpotts|Ague|2009|p=20}}

A cooling lava flow shrinks, and this fractures the flow. Basalt flows show a characteristic pattern of fractures. The uppermost parts of the flow show irregular downward-splaying fractures, while the lower part of the flow shows a very regular pattern of fractures that break the flow into five- or six-sided columns. The irregular upper part of the solidified flow is called the ''entablature'', while the lower part that shows [columnar jointing](/source/columnar_jointing) is called the ''colonnade''. (The terms are borrowed from Greek temple architecture.) Likewise, regular vertical patterns on the sides of columns, produced by cooling with periodic fracturing, are described as ''chisel marks''. Despite their names, these are natural features produced by cooling, thermal contraction, and fracturing.{{sfn|Philpotts|Ague|2009|pp=55-56}}

As lava cools, crystallizing inwards from its edges, it expels gases to form vesicles at the lower and upper boundaries. These are described as ''pipe-stem vesicles'' or ''pipe-stem amygdales''. Liquids expelled from the cooling crystal mush rise upwards into the still-fluid center of the cooling flow and produce vertical ''vesicle cylinders''. Where these merge towards the top of the flow, they form sheets of vesicular basalt and are sometimes capped with gas cavities that sometimes fill with secondary minerals. The beautiful [amethyst](/source/amethyst) geodes found in the flood basalts of South America formed in this manner.{{sfn|Philpotts|Ague|2009|pp=58-59}}

Flood basalts typically crystallize little before they cease flowing, and, as a result, flow textures are uncommon in less silicic flows.{{sfn|Philpotts|Ague|2009|p=48}} On the other hand, [flow banding](/source/flow_banding) is common in felsic flows.{{sfn|Philpotts|Ague|2009|p=72}}

==Morphology==

[[Image:Lava entering sea - Hawaii.png|thumb|Lava entering the sea to expand the [big island of Hawaii](/source/Hawaii_(island)), [Hawai{{okina}}i Volcanoes National Park](/source/Hawai%7B%7Bokina%7D%7Di_Volcanoes_National_Park)]]
The morphology of lava describes its surface form or texture. More fluid basaltic lava flows tend to form flat sheet-like bodies, whereas viscous rhyolite lava flows form knobbly, blocky masses of rock. Lava erupted underwater has its own distinctive characteristics.

[[Image:Three Waikupanaha and one Ki lava ocean entries w-edit2.jpg|thumb|Lava enters the [Pacific](/source/Pacific) at [the Big Island of Hawaii](/source/Hawaii_(island)). ]]

=== {{okina}}A{{okina}}ā ===
{{hatnote|The following subsection is about the types of lava flow. For the sculpture of a god from the Pacific island of Rurutu, see [Statue of A'a from Rurutu](/source/Statue_of_A'a_from_Rurutu).}}
[[Image:Aa large.jpg|thumb|Glowing {{okina}}a{{okina}}ā flow front advancing over pāhoehoe on the coastal plain of [Kīlauea](/source/K%C4%ABlauea) in [Hawaii](/source/Hawaii), United States]]
''{{okina}}A{{okina}}ā'' (also spelled ''aa'', ''a{{okina}}a'', ''{{okina}}a{{okina}}a'', and ''a-aa'', and pronounced {{IPA|haw|ʔəˈʔaː|}} or {{IPAc-en|ˈ|ɑː|(|ʔ|)|ɑː}}) is one of three basic types of flow lava. {{okina}}A{{okina}}ā is basaltic lava characterized by a rough or rubbly surface composed of broken lava blocks called clinker. The word is  [Hawaiian](/source/Hawaiian_language) meaning "stony rough lava", but also to "burn" or "blaze";<ref>{{cite dictionary|title={{okina}}a{{okina}}ā|url=http://www.wehewehe.org/gsdl2.5/cgi-bin/hdict?d=D10|dictionary=Hawaiian Dictionary (Hwn to Eng)|archive-url=https://archive.today/20121228131017/http://www.wehewehe.org/gsdl2.5/cgi-bin/hdict?d=D10 |archive-date=28 December 2012}}</ref> it was introduced as a technical term in geology by [Clarence Dutton](/source/Clarence_Dutton).<ref name="Kemp">{{cite book |first1=James Furman |last1=Kemp |title=A handbook of rocks for use without the microscope: with a glossary of the names of rocks and other lithological terms |volume=5 |location=New York |publisher=D. Van Nostrand |year=1918 |pages=180, 240 |url=https://books.google.com/books?id=tHQNAAAAYAAJ&pg=PA180}}</ref><ref name="dutton">{{cite journal |page=240 |first1=C. E. |last1=Dutton |journal=Annual Report U.S. Geological Survey |volume=4 |title=Hawaiian volcanoes |year=1883 |number=95}}</ref>

The loose, broken, and sharp, spiny surface of an {{okina}}a{{okina}}ā flow makes [hiking](/source/hiking) difficult and slow. The clinkery surface actually covers a massive dense core, which is the most active part of the flow. As pasty lava in the core travels downslope, the clinkers are carried along at the surface. At the leading edge of an {{okina}}a{{okina}}ā flow, however, these cooled fragments tumble down the steep front and are buried by the advancing flow. This produces a layer of lava fragments both at the bottom and top of an {{okina}}a{{okina}}ā flow.{{sfn|Schmincke|2003|pp=131-132}}

Accretionary lava balls as large as {{convert|3|m|0|abbr=off}} are common on {{okina}}a{{okina}}ā flows.<ref>{{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=0-8248-0832-0 |page=23 |edition=2nd}}</ref> {{okina}}A{{okina}}ā is usually of higher viscosity than pāhoehoe. Pāhoehoe can turn into {{okina}}a{{okina}}ā if it becomes turbulent from meeting impediments or steep slopes.{{sfn|Schmincke|2003|pp=131-132}}

The sharp, angled texture makes {{okina}}a{{okina}}ā a strong [radar](/source/radar) reflector, and can easily be seen from an orbiting satellite (bright on [Magellan](/source/Magellan_probe) pictures).<ref name="VenusAa">{{cite web | url=http://www.lpi.usra.edu/publications/slidesets/hawaii/ | title=Radar Studies of Lava Flows | publisher=Lunar and Planetary Institute | work=Volcanic Features of Hawaii and Other Worlds | access-date=18 March 2017 | author=McGounis-Mark, Peter}}</ref>

{{okina}}A{{okina}}ā lavas typically erupt at temperatures of {{convert|1050|to|1150|°C}} or greater.<ref>{{cite journal |last1=Pinkerton |first1=Harry |last2=James |first2=Mike |last3=Jones |first3=Alun |title=Surface temperature measurements of active lava flows on Kilauea volcano, Hawaiʻi |journal=Journal of Volcanology and Geothermal Research |date=March 2002 |volume=113 |issue=1–2 |pages=159–176 |doi=10.1016/S0377-0273(01)00257-8|bibcode=2002JVGR..113..159P }}</ref><ref>{{cite journal |last1=Cigolini |first1=Corrado |last2=Borgia |first2=Andrea |last3=Casertano |first3=Lorenzo |title=Intra-crater activity, aa-block lava, viscosity and flow dynamics: Arenal Volcano, Costa Rica |journal=Journal of Volcanology and Geothermal Research |date=March 1984 |volume=20 |issue=1–2 |pages=155–176 |doi=10.1016/0377-0273(84)90072-6|bibcode=1984JVGR...20..155C }}</ref>

===Pāhoehoe===
thumb|upright|Pāhoehoe lava from Kīlauea volcano, Hawaii, United States
''Pāhoehoe'' (also spelled ''pahoehoe'', from Hawaiian {{IPA|haw|paːˈhoweˈhowe|}}<ref>{{cite dictionary|title=pāhoehoe|url=http://www.wehewehe.org/gsdl2.5/cgi-bin/hdict?d=D16177|dictionary=Hawaiian Dictionary (Hwn to Eng)|archive-url=https://archive.today/20120918075604/http://www.wehewehe.org/gsdl2.5/cgi-bin/hdict?d=D16177 |archive-date=18 September 2012}}</ref> meaning "smooth, unbroken lava") is basaltic lava that has a smooth, billowy, undulating, or ropy surface. These surface features are due to the movement of very fluid lava under a congealing surface crust. The Hawaiian word was introduced as a technical term in geology by [Clarence Dutton](/source/Clarence_Dutton).<ref name="Kemp" /><ref name=dutton/>

A pāhoehoe flow typically advances as a series of small lobes and toes that continually break out from a cooled crust. It also forms [lava tube](/source/lava_tube)s where the minimal heat loss maintains a low viscosity. The surface texture of pāhoehoe flows varies widely, displaying all kinds of bizarre shapes often referred to as lava sculpture. With increasing distance from the source, pāhoehoe flows may change into {{okina}}a{{okina}}ā flows in response to heat loss and consequent increase in viscosity.{{sfn|Schmincke|2003|pp=128-132}} Experiments suggest that the transition takes place at a temperature between {{convert|1200 and 1170|C}}, with some dependence on shear rate.<ref>{{cite journal |last1=Sehlke |first1=A. |last2=Whittington |first2=A. |last3=Robert |first3=B. |last4=Harris |first4=A. |last5=Gurioli |first5=L. |last6=Médard |first6=E. |title=Pahoehoe to 'a'a transition of Hawaiian lavas: an experimental study |journal=Bulletin of Volcanology |date=17 October 2014 |volume=76 |issue=11 |page=876 |doi=10.1007/s00445-014-0876-9|bibcode=2014BVol...76..876S |s2cid=129019507 }}</ref><ref name=Sonder/> Pahoehoe lavas typically have a temperature of {{convert|1100|to|1200|°C}}.{{sfn|Philpotts|Ague|2009|p=20}}

On the Earth, most lava flows are less than {{convert|10|km|mi|abbr=on}} long, but some pāhoehoe flows are more than {{convert|50|km|mi|abbr=on}} long.<ref name="LavaLength">{{cite web | url=http://volcano.si.edu/learn_galleries.cfm?p=12 | title=Types and Processes Gallery: Lava Flows | publisher=[Smithsonian Institution](/source/Smithsonian_Institution) | work=Global Volcanism Program | date=2013 | access-date=1 December 2015}}</ref> Some flood basalt flows in the geologic record extend for hundreds of kilometres.{{sfn|Philpotts|Ague|2009|p=53}}

The rounded texture makes pāhoehoe a poor radar reflector, and is difficult to see from an orbiting satellite (dark on Magellan picture).<ref name="VenusAa"/>

=== Blocks ===
[[File:Block lava in Lassen Volcanic National Park.jpg|thumb|Block lava at [Fantastic Lava Beds near Cinder Cone](/source/Cinder_Cone_and_the_Fantastic_Lava_Beds) in Lassen Volcanic National Park]]
Block lava flows are typical of andesitic lavas from stratovolcanoes. They behave in a similar manner to {{okina}}a{{okina}}ā flows but their more viscous nature causes the surface to be covered in smooth-sided angular fragments (blocks) of solidified lava instead of clinkers. As with {{okina}}a{{okina}}ā flows, the molten interior of the flow, which is kept insulated by the solidified blocky surface, advances over the rubble that falls off the flow front. They also move much more slowly downhill and are thicker in depth than {{okina}}a{{okina}}ā flows.
{{sfn|Schmincke|2003|p=132}}

===Pillows===
{{Main|Pillow lava}}
[[Image:Nur05018-Pillow lavas off Hawaii.jpg|thumb|[Pillow lava](/source/Pillow_lava) on the ocean floor near Hawaii]]
''Pillow lava'' is the lava structure typically formed when lava emerges from an [underwater volcanic vent](/source/submarine_volcano) or [subglacial volcano](/source/subglacial_volcano) or a lava flow enters the ocean. The viscous lava gains a solid crust on contact with the water, and this crust cracks and oozes additional large blobs or "pillows" as more lava emerges from the advancing flow. Since water covers the majority of [Earth](/source/Earth)'s surface and most volcanoes are situated near or under bodies of water, pillow lava is very common.<ref>{{cite journal |journal=Bulletin of the Geological Society of America |last1=Lewis |first1=J.V. |title=Origin of pillow lavas |volume=25 |year=1914 |issue=1 |page=639 |doi=10.1130/GSAB-25-591 |bibcode=1914GSAB...25..591L |url=https://books.google.com/books?id=ItaPAAAAMAAJ&pg=PA639}}</ref>

== Landforms ==
Because it is formed from viscous molten rock, lava flows and eruptions create distinctive formations, landforms and topographical features from the macroscopic to the microscopic.

===Volcanoes===
{{Main|Volcano}}
[[Image:Arenallong.jpg|thumb|[Arenal Volcano](/source/Arenal_Volcano), Costa Rica, is a [stratovolcano](/source/stratovolcano).]]
Volcanoes are the primary landforms built by repeated eruptions of lava and ash over time. They range in shape from [shield volcano](/source/shield_volcano)es with broad, shallow slopes formed from predominantly effusive eruptions of relatively fluid basaltic lava flows, to steeply-sided [stratovolcano](/source/stratovolcano)es (also known as composite volcanoes) made of alternating layers of ash and more viscous lava flows typical of intermediate and felsic lavas.{{sfn|Philpotts|Ague|2009|pp=59-73}}

A [caldera](/source/caldera), which is a large subsidence crater, can form in a stratovolcano, if the magma chamber is partially or wholly emptied by large explosive eruptions; the summit cone no longer supports itself and thus collapses in on itself afterwards.{{sfn|Schmincke|2003|pp=147-148}} Such features may include volcanic crater lakes and lava domes after the event.{{sfn|Schmincke|2003|pp=132, 286}} However, calderas can also form by non-explosive means such as gradual magma subsidence. This is typical of many shield volcanoes.{{sfn|Schmincke|2003|pp=149-151}}

===Cinder and spatter cones===
{{Main|Volcanic cone}}
[Cinder cone](/source/Cinder_cone)s and spatter cones are small-scale features formed by lava accumulation around a small vent on a volcanic edifice. Cinder cones are formed from [tephra](/source/tephra) or [ash](/source/Volcanic_ash) and [tuff](/source/tuff) which is thrown from an explosive vent. Spatter cones are formed by accumulation of molten volcanic slag and cinders ejected in a more liquid form.{{sfn|Macdonald|Abbott|Peterson|1983|pp=26-17}}

===Kīpukas===
{{Main|Kīpuka}}
Another [Hawaiian English](/source/Hawaiian_English) term derived from the [Hawaiian language](/source/Hawaiian_language), a kīpuka denotes an elevated area such as a hill, ridge or old lava dome inside or downslope from an area of active volcanism. New lava flows will cover the surrounding land, isolating the kīpuka so that it appears as a (usually) forested island in a barren lava flow.{{sfn|Macdonald|Abbott|Peterson|1983|pp=22-23}}

===Lava domes and coulées===
{{Main|Lava dome}}
[[Image:Valle Grande dome.jpg|thumb|A forested lava dome in the midst of the Valle Grande, the largest meadow in the [Valles Caldera National Preserve](/source/Valles_Caldera), New Mexico, United States]]
Lava domes are formed by the extrusion of viscous felsic magma. They can form prominent rounded protuberances, such as at [Valles Caldera](/source/Valles_Caldera). As a volcano extrudes silicic lava, it can form an ''inflation dome'' or ''endogenous dome'', gradually building up a large, pillow-like structure which cracks, fissures, and may release cooled chunks of rock and rubble. The top and side margins of an inflating lava dome tend to be covered in fragments of rock, [breccia](/source/breccia) and ash.{{sfn|Schmincke|2003|pp=132-138, 152-153}}

Examples of lava dome eruptions include the [Novarupta](/source/Novarupta) dome, and successive lava domes of [Mount St Helens](/source/Mount_St_Helens).{{sfn|Schmincke|2003|pp=132-134}}

When a dome forms on an inclined surface it can flow in short thick flows called coulées (dome flows). These flows often travel only a few kilometres from the vent.{{sfn|Schmincke|2003|pp=132-138}}

===Lava tubes===
{{Main|Lava tube}}
Lava tubes are formed when a flow of relatively fluid lava cools on the upper surface sufficiently to form a crust. Beneath this crust, which being made of rock is an excellent insulator, the lava can continue to flow as a liquid. When this flow occurs over a prolonged period of time the lava conduit can form a tunnel-like aperture or ''lava tube'', which can conduct molten rock many kilometres from the vent without cooling appreciably. Often these lava tubes drain out once the supply of fresh lava has stopped, leaving a considerable length of open tunnel within the lava flow.{{sfn|Macdonald|Abbott|Peterson|1983|pp=23,26-29}}

Lava tubes are known from the modern day eruptions of Kīlauea,{{sfn|Macdonald|Abbott|Peterson|1983|p=27}} and significant, extensive and open lava tubes of Tertiary age are known from North [Queensland](/source/Queensland), [Australia](/source/Australia), some extending for {{convert|15|km|0|abbr=off}}.<ref>{{cite journal |last1=Atkinson |first1=A. |last2=Griffin |first2=T. J. |last3=Stephenson |first3=P. J. |title=A major lava tube system from Undara Volcano, North Queensland |journal=Bulletin Volcanologique |date=June 1975 |volume=39 |issue=2 |pages=266–293 |doi=10.1007/BF02597832|bibcode=1975BVol...39..266A |s2cid=129126355 }}</ref>

===Lava lakes===
{{Main|Lava lake}}
[[Image:Dikes-large.jpg|thumb|[Shiprock](/source/Shiprock), New Mexico, United States: a [volcanic neck](/source/volcanic_neck) in the distance, with a radiating [dike](/source/dike_(geology)) on its south side]]

Rarely, a volcanic cone may fill with lava but not erupt. Lava which pools within the caldera is known as a lava lake.{{sfn|Schmincke|2003|p=27}} Lava lakes do not usually persist for long, either draining back into the magma chamber once pressure is relieved (usually by venting of gases through the caldera), or by draining via eruption of lava flows or pyroclastic explosion.

There are only a few sites in the world where permanent lakes of lava exist. These include:
* [Mount Erebus](/source/Mount_Erebus), [Antarctica](/source/Antarctica)<ref name="lava-lake">{{cite journal |last1=Lev |first1=Einat |last2=Ruprecht |first2=Philipp |last3=Oppenheimer |first3=Clive |last4=Peters |first4=Nial |last5=Patrick |first5=Matt |last6=Hernández |first6=Pedro A. |last7=Spampinato |first7=Letizia |last8=Marlow |first8=Jeff |title=A global synthesis of lava lake dynamics |journal=Journal of Volcanology and Geothermal Research |date=September 2019 |volume=381 |pages=16–31 |doi=10.1016/j.jvolgeores.2019.04.010|bibcode=2019JVGR..381...16L |s2cid=182844266 }}</ref>
* [Erta Ale](/source/Erta_Ale), [Ethiopia](/source/Ethiopia){{sfn|Philpotts|Ague|2009|p=61}}
* [Nyiragongo](/source/Nyiragongo), [Democratic Republic of Congo](/source/Democratic_Republic_of_Congo)<ref>{{cite journal |last1=Burgi |first1=P.-Y. |last2=Darrah |first2=T. H. |last3=Tedesco |first3=D. |last4=Eymold |first4=W. K. |title=Dynamics of the Mount Nyiragongo lava lake: DYNAMICS OF THE MT. NYIRAGONGO LAVA LAKE |journal=Journal of Geophysical Research: Solid Earth |date=May 2014 |volume=119 |issue=5 |pages=4106–4122 |doi=10.1002/2013JB010895|doi-access=free }}</ref>
* [Ambrym](/source/Ambrym), [Vanuatu](/source/Vanuatu).<ref name="lava-lake"/>

===Lava delta===
{{Main|Lava delta}}
Lava deltas form wherever [sub-aerial](/source/subaerial) flows of lava enter standing bodies of water. The lava cools and breaks up as it encounters the water, with the resulting fragments filling in the [seabed topography](/source/seabed_topography) such that the sub-aerial flow can move further offshore. Lava deltas are generally associated with large-scale, effusive type basaltic volcanism.<ref>{{cite journal |last1=Bosman |first1=Alessandro |last2=Casalbore |first2=Daniele |last3=Romagnoli |first3=Claudia |last4=Chiocci |first4=Francesco Latino |title=Formation of an 'a'ā lava delta: insights from time-lapse multibeam bathymetry and direct observations during the Stromboli 2007 eruption |journal=Bulletin of Volcanology |date=July 2014 |volume=76 |issue=7 |page=838 |doi=10.1007/s00445-014-0838-2|bibcode=2014BVol...76..838B |s2cid=129797425 }}</ref>

== Lava fountains ==
[[Image:Lava fountain at Kilauea.jpg|thumb|upright|Lava fountain at [Kīlauea](/source/K%C4%ABlauea)]]

A '''lava fountain''' is a [volcanic](/source/volcano) phenomenon in which lava is forcefully but non-explosively ejected from a [crater](/source/Volcanic_crater), vent, or [fissure](/source/fissure_vent). The highest lava fountain recorded was during the 23 November 2013 eruption of [Mount Etna](/source/Mount_Etna) in Italy, which reached a stable height of around {{convert|2500|m|ft|sigfig=2|abbr=on}} for 18 minutes, briefly peaking at a height of {{convert|3400|m|ft|sigfig=2|abbr=on}}.<ref>{{cite journal |last1=Bonaccorso |first1=A. |last2=Calvari |first2=S. |last3=Linde |first3=A. |last4=Sacks |first4=S. |title=Eruptive processes leading to the most explosive lava fountain at Etna volcano: The 23 November 2013 episode |journal=Geophysical Research Letters |date=28 July 2014 |volume=41 |issue=14 |pages=4912–4919 |doi=10.1002/2014GL060623 |bibcode=2014GeoRL..41.4912B |s2cid=129813334 |quote=To the best of our knowledge, it reached the highest value ever measured for a lava fountain on Earth.}}</ref> Lava fountains may occur as a series of short pulses, or a continuous jet of lava. They are commonly associated with [Hawaiian eruption](/source/Hawaiian_eruption)s.{{sfn|Macdonald|Abbott|Peterson|1983|p=9}}

==Hazards==

Lava flows are enormously destructive to property in their path. However, casualties are rare since flows are usually slow enough for people and animals to escape, though this is dependent on the viscosity of the lava. Nevertheless, injuries and deaths have occurred, either because they had their escape route cut off, because they got too close to the flow<ref name=usgs>[https://www.usgs.gov/programs/VHP/lava-flows-destroy-everything-their-path Lava Flows and Their Effects] USGS</ref> or, more rarely, if the lava flow front travels too quickly. This notably happened during the eruption of [Nyiragongo](/source/Mount_Nyiragongo) in Zaire (now [Democratic Republic of the Congo](/source/Democratic_Republic_of_the_Congo)). On the night of 10 January 1977, a crater wall was breached and a fluid lava lake drained out in under an hour. The resulting flow sped down the steep slopes at up to {{convert|100|km/h|abbr=on}}, and overwhelmed several villages while residents were asleep. As a result of this disaster, the mountain was designated a [Decade Volcano](/source/Decade_Volcano) in 1991.<ref name=hvo>[https://hvo.wr.usgs.gov/volcanowatch/2002/02_01_31.html Nyiragongo – Could it happen here?] [USGS](/source/United_States_Geological_Survey) [Hawaiian Volcano Observatory](/source/Hawaiian_Volcano_Observatory)</ref>

[Deaths attributed to volcanoes](/source/List_of_volcanic_eruptions_by_death_toll) frequently have a different cause. For example, volcanic ejecta, [pyroclastic flow](/source/pyroclastic_flow) from a collapsing lava dome, [lahar](/source/lahar)s, poisonous gases that travel ahead of lava, or explosions caused when the flow comes into contact with water.<ref name=usgs /> A particularly dangerous area is called a [lava bench](/source/lava_bench). This very young ground will typically break off and fall into the sea.

Areas of recent lava flows continue to represent a hazard long after the lava has cooled. Where young flows have created new lands, land is more unstable and can break off into the sea. Flows often crack deeply, forming dangerous chasms, and a fall against {{okina}}a{{okina}}ā lava is similar to falling against broken glass. Rugged hiking boots, long [pants](/source/Trousers), and gloves are recommended when crossing lava flows.

Diverting a lava flow is extremely difficult, but it can be accomplished in some circumstances, as was once partially achieved in [Vestmannaeyjar](/source/Vestmannaeyjar), Iceland.<ref>{{cite web |url=http://indianapublicmedia.org/amomentofscience/vestmannaeyjar-town-fought-volcano-won/ |title=Vestmannaeyjar, The Town That Fought A Volcano And Won |last1=Sonstroem |first1=Eric |date=14 September 2010 |website=indianapublicmedia.org |publisher=Indiana Public Media |access-date=24 November 2017 |archive-date=23 February 2017 |archive-url=https://web.archive.org/web/20170223203301/http://indianapublicmedia.org/amomentofscience/vestmannaeyjar-town-fought-volcano-won/ }}</ref> The optimal design of simple, low-cost barriers that divert lava flows is an area of ongoing research.<ref>{{cite journal|url=https://www.nature.com/articles/ngeo2470|title=Diverting lava flows in the lab|last1=Dietterich |first1=Hannah|last2=Cashman |first2=Katherine|last3=Rust |first3=Alison |last4=Lev |first4=Einat |date=2015 |journal=Nature Geoscience |volume=8|issue=7|pages=494–496|doi=10.1038/ngeo2470|bibcode=2015NatGe...8..494D|url-access=subscription}}</ref><ref>{{cite journal|title=Viscous free-surface flows past cylinders|last1=Hinton |first1=Edward|last2=Hogg |first2=Andrew|last3=Huppert |first3=Herbert |date=2020 |journal=Physical Review Fluids |volume=5|number=84101|article-number=084101|doi=10.1103/PhysRevFluids.5.084101|bibcode=2020PhRvF...5h4101H|hdl=1983/f52f7078-5936-4e37-9d79-be456f08eb5c |s2cid=225416948|hdl-access=free}}</ref>

===Towns destroyed by lava flows===
[[Image:Kalapana house destroyed by lava.jpg|thumb|right|Lava can easily destroy entire towns. This picture shows one of over 100 houses destroyed by the lava flow in [Kalapana, Hawaii](/source/Kalapana%2C_Hawaii), United States, in 1990.]]
* The [Nisga'a](/source/Nisga'a) villages of [Lax Ksiluux](/source/Lax_Ksiluux%2C_British_Columbia) and Wii Lax K'abit in northwestern [British Columbia](/source/British_Columbia), Canada, were destroyed by thick lava flows during the eruption of [Tseax Cone](/source/Tseax_Cone) in the 1700s.
* [Garachico](/source/Garachico) on the island of [Tenerife](/source/Tenerife) was destroyed by the [eruption of Trevejo (1706)](/source/eruption_of_Trevejo_(1706)) (rebuilt).
* Keawaiki, Hawaii, 1859 (abandoned)
* [San Sebastiano al Vesuvio, Italy](/source/San_Sebastiano_al_Vesuvio), destroyed in 1944 by the most recent eruption of [Mount Vesuvius](/source/Mount_Vesuvius) during the Allies' occupation of southern [Italy](/source/Italy) (rebuilt)
* Koae and [Kapoho, Hawaii](/source/Kapoho%2C_Hawaii), were both destroyed by the same eruption of [Kīlauea](/source/K%C4%ABlauea) in January, 1960<ref>{{cite web |url=http://vhca.info/1959.htm |title=Article – Our Volcanic History by Gladys Flanders |publisher=Vhca.info |date=1959-11-15 |access-date=2013-12-08 |archive-date=2016-03-03 |archive-url=https://web.archive.org/web/20160303215410/http://vhca.info/1959.htm }}</ref> (abandoned).
* [Kalapana, Hawaii](/source/Kalapana%2C_Hawaii), was destroyed by the eruption of the [Kīlauea volcano](/source/K%C4%ABlauea_volcano) in 1990 (abandoned).
* [Kapoho, Hawaii](/source/Kapoho%2C_Hawaii), was largely inundated by lava in June 2018, with its subdivision [Vacationland Hawaii](/source/Vacationland_Hawaii) being completely destroyed.

===Towns damaged by lava flows===
* [Catania, Italy](/source/Catania%2C_Italy), in the [1669 Etna eruption](/source/1669_Etna_eruption)<ref name="EtnaAGU2004">{{cite book | title=Mount Etna:Volcano Laboratory | publisher=[American Geophysical Union](/source/American_Geophysical_Union) (Geophysical Monograph 143) | editor=Bonaccorso, A. | year=2004 | location=Washington D.C. | page=3 | isbn=978-0-87590-408-5| display-editors=etal }}</ref> (rebuilt)
* [Sale'aula](/source/Saleaula), Samoa, by eruptions of [Mt Matavanu](/source/Mt_Matavanu) between 1905 and 1911
* [Mascali](/source/Mascali), Italy, almost destroyed by the eruption of [Mount Etna](/source/Mount_Etna) in 1928 (rebuilt)<ref name="Duncan_etal_1996">{{cite journal | title=The 1928 Eruption of Mount Etna Volcano, Sicily, and the Destruction of the Town of Mascali | first1=A.M. | last1=Duncan | first2=C. | last2=Dibben | first3=D.K. | last3=Chester | first4=J.E. |last4=Guest | journal=Disasters | year=1996 | volume=20 | issue=1 | pages=1–20 | doi=10.1111/j.1467-7717.1996.tb00511.x| pmid=8867507 | bibcode=1996Disas..20....1D }}</ref>
* [Parícutin](/source/Par%C3%ADcutin) (village after which the volcano was named) and [San Juan Parangaricutiro](/source/Nuevo_San_Juan_Parangaricutiro%2C_Michoac%C3%A1n), Mexico, by [Parícutin](/source/Par%C3%ADcutin) from 1943 to 1952
* [Heimaey, Iceland](/source/Heimaey), in the 1973 [Eldfell](/source/Eldfell) eruption (rebuilt)
* [Piton Sainte-Rose](/source/Piton_Sainte-Rose), Reunion island, in 1977<ref name="Reunion1977">{{cite web | url=http://planet-terre.ens-lyon.fr/image-de-la-semaine/Img240-2008-06-23.xml | title=Église et gendarmerie envahies mais non détruites par la coulée d'avril 1977 de Piton Sainte Rose, île de La Réunion | publisher=[ENS de Lyon](/source/%C3%89cole_normale_sup%C3%A9rieure_de_Lyon) | work=Planet Terre | date=23 June 2008 | access-date=26 May 2018 | author=Thomas, Pierre | language=fr | url-status=dead | archive-url=https://web.archive.org/web/20180416125629/http://planet-terre.ens-lyon.fr/image-de-la-semaine/Img240-2008-06-23.xml | archive-date=16 April 2018}}</ref>
* [Royal Gardens, Hawaii](/source/Royal_Gardens%2C_Hawaii), by the eruption of [Kilauea](/source/Kilauea) in 1986–87 (abandoned)
* [Goma](/source/Goma), [Democratic Republic of Congo](/source/Democratic_Republic_of_Congo), in the eruption of [Nyiragongo](/source/Nyiragongo) in 2002<ref>{{cite web|url=https://volcano.si.edu/volcano.cfm?vn=223030|title=Global Volcanism Program - Nyiragongo|website=volcano.si.edu}}</ref>
* Los Llanos de Aridane ([Todoque](/source/Todoque) neighbourhood) and [El Paso](/source/El_Paso_(La_Palma)) (El Paraíso neighbourhood) on [La Palma](/source/La_Palma) in the [2021 Cumbre Vieja volcanic eruption](/source/2021_Cumbre_Vieja_volcanic_eruption)<ref>{{Cite news|date=2021-09-25|title=La Palma volcano: Visual guide to what happened|language=en-GB|work=BBC News|url=https://www.bbc.com/news/world-europe-58681233|access-date=2021-09-25}}</ref><ref>{{Cite web|date=2021-09-23|title=Inge y Rainer, los dueños de la 'casa milagro' de La Palma: "Aunque no podemos ir, nos alivia que siga en pie"|url=https://www.elmundo.es/papel/historias/2021/09/23/614c645021efa01e388b4627.html|access-date=2021-09-25|quote=... en El Paraíso, justo la pedanía más afectada hasta la fecha por el río de lava del volcán. Más de la mitad de las casas, incluido el colegio local, ya han sido devoradas por la ceniza.|trans-quote=... in El Paraíso, just the district most affected to date by the river of lava from the volcano. More than half of the houses, including the local school, have already been consumed by ash.|website=El Mundo|language=es}}</ref><ref name="Todoque2021">{{cite news | url=https://www.elnacional.cat/es/sociedad/barrio-todoque-desaparece-totalmente-bajo-lava-volcan-la-palma_655610_102.html | title=El barrio de Todoque desaparece totalmente bajo la lava del volcán de La Palma | work=elnacional.cat | date=10 October 2021 | access-date=18 January 2022 | author=Sagrera, Berto | location=Barcelona | language=es}}</ref>

===Towns destroyed by tephra===
[Tephra](/source/Tephra) is fragmental material, including solidified lava fragments, that has been ejected from a volcano during a volcanic eruption; it can take the form of [volcanic ash](/source/volcanic_ash), [lapilli](/source/lapilli), [volcanic bomb](/source/volcanic_bomb)s or [volcanic block](/source/volcanic_block)s.
* [Pompeii](/source/Pompeii), Italy, in the eruption of [Mount Vesuvius](/source/Mount_Vesuvius) in 79 AD
* [Herculaneum](/source/Herculaneum), Italy, in the eruption of [Mount Vesuvius](/source/Mount_Vesuvius) in 79 AD
* [Akrotiri](/source/Akrotiri_(prehistoric_city)), on the Greek island of [Santorini](/source/Santorini), was buried by pumice and ash from the [Minoan eruption](/source/Minoan_eruption) around 1600 BCE.<ref name="Michailidou_2013">{{cite book |last1=Michailidou |first1=A. |year=2013 |chapter=The final settlement at Akrotiri on Thera: the buildings, the people, and the eruption  |title=1600 – Cultural change in the shadow of the Thera-Eruption? |series=Tagungen des Landesmuseums für Vorgeschichte Halle |volume=9 |editor1-last=Legler |editor1-first=K. |editor2-last=Schwarz |editor2-first=M. |editor3-last=Schwarz |editor3-first=W. |editor4-last=Swieder |editor4-first=A. |display-editors=1 |publisher=Landesamt für Denkmalpflege und Archäologie Sachsen-Anhalt – Landesmuseum für Vorgeschichte Halle (Saale) |pages=137–148 |issn=1867-4402 |isbn=978-3-944507-00-2}}</ref>
* [Cerén](/source/Joya_de_Cer%C3%A9n), El Salvador, in the eruption of [Ilopango](/source/Lake_Ilopango) between 410 and 535 AD<ref>Bundschuh, J. and Alvarado, G. E (editors) (2007) ''Central America: Geology, Resources and Hazards'', volume 1, p. 56, London, Taylor and Francis</ref>
* [Sumbawa Island](/source/Sumbawa_Island), Indonesia, in the eruption of [Mount Tambora](/source/Mount_Tambora) in 1815
* [Plymouth, Montserrat](/source/Plymouth%2C_Montserrat), in 1995. Plymouth was the capital and only port of entry for [Montserrat](/source/Montserrat) and had to be completely abandoned, along with over half of the island. It is still the ''[de jure](/source/de_jure)'' capital.

== See also ==
{{Portal|Volcanoes|Geology}}
* {{annotated link|Blue lava}}
* {{annotated link|Lava planet}}
* {{annotated link|Laze (geology)}}
* {{annotated link|Vog}}

==References==
{{Reflist}}

==External links==
{{Wiktionary|lava|aa|pahoehoe}}
{{Commons and category|lava}}
* {{Cite EB1911 |wstitle=Lava |volume=16 |pages=289–290 |short=1}}
* [https://volcanoes.usgs.gov/images/pglossary/aa.php USGS definition of {{okina}}A{{okina}}ā]
* [https://volcanoes.usgs.gov/images/pglossary/pahoehoe.php USGS definition of Pāhoehoe]
* [https://volcanoes.usgs.gov/images/pglossary/pahoehoe_ropy.php USGS definition of Ropy Pāhoehoe]
* [https://web.archive.org/web/20060116130656/http://volcano.und.edu/vwdocs/vwlessons/havo.html Volcanic landforms of Hawaii]
* [https://volcanoes.usgs.gov/Hazards/What/Lava/lavaflow.html USGS hazards associated with lava flows]
* [https://hvo.wr.usgs.gov/volcanowatch/2002/02_01_31.html Hawaiian Volcano Observatory Volcano Watch newsletter article on Nyiragongo eruptions, 31 January 2002]
* [http://link.brightcove.com/services/link/bcpid687239786/bclid736245450/bctid736245427 National Geographic lava video] ({{Webarchive|url=https://web.archive.org/web/20160303171558/http://link.brightcove.com/services/link/bcpid687239786/bclid736245450/bctid736245427 |date=2016-03-03 }}) Retrieved 23 August 2007

{{Basalt}}
{{Authority control}}

Category:Eruption products
Category:Glassforming liquids and melts
Category:Igneous rocks
Category:Volcanic degassing
Category:Volcanism

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Adapted from the Wikipedia article [Lava](https://en.wikipedia.org/wiki/Lava) by Wikipedia contributors ([contributor history](https://en.wikipedia.org/wiki/Lava?action=history)). Available under [Creative Commons Attribution-ShareAlike 4.0 International](https://creativecommons.org/licenses/by-sa/4.0/). Changes may have been made.