Volcanism on the Moon

File:Lava flows in Mare Imbrium (AS15-M-1558).png lava flows of Mare Imbrium forming wrinkle ridges]]

In 1610, Italian astronomer Galileo Galilei misinterpreted the lunar lava plains as seas while observing the Moon through an early telescope. Galilei therefore dubbed them maria after the Latin word for "seas". The bowl-shaped depressions distributed throughout the lunar landscape were first suggested to be volcanoes in 1665 by British chemist Robert Hooke. Their volcanic origin was bolstered by their similarity to the Phlegraean Fields craters in Italy, although much larger. French astronomer Pierre Puiseux proposed that the Moon's craters were collapsed volcanic domes that had vented all their gases. Pierre-Simon Laplace, another French astronomer, proposed in the 18th century that meteorites were volcanic projectiles ejected from lunar craters during major eruptions.{{cite book|last=Frankel|first=Charles|title=Worlds on Fire: Volcanoes on the Earth, the Moon, Mars, Venus and Io|chapter=Volcanism on the Moon|publisher=Cambridge University Press|pages=64, 65, 66|year=2005|isbn=978-0-521-80393-9}} British astronomer William Herschel, in one of his early papers, claimed to have seen three volcanoes on the Moon in the late 1700s, which later turned out to be earthshine.{{Cite Q|Q19072944|pages=56–60}}

The origin of lunar craters remained controversial throughout the first half of the 20th century, with volcano supporters arguing that bright rays fanning out of some craters were streaks of volcanic ash similar to those found at Mount Aso in Japan. Astronomers also reported flashes of light and red clouds over the Alphonsus and Aristarchus craters. Evidence collected during the Apollo program (1961–1972) and from uncrewed spacecraft of the same period proved conclusively that meteoric impact, or impact by asteroids for larger craters, was the origin of almost all lunar craters, and by implication, most craters on other bodies as well.{{Citation needed|date=April 2025}} It was initially believed that meteorite impacts could not be responsible for circular craters and that they must have all been due to volcanic activity, as meteorites would create elliptic craters when impacting at an angle. However, research has shown that meteorites would have sufficient energy to cause a circular explosin upon impact, causing circular craters, unless they were to hit at an extraordinarily small angle to the horizontal.{{Cite web |title=Why are impact craters always round? Most incoming objects must strike at some angle from vertical, so why don't the majority of impact sites have elongated, teardrop shapes? |url=https://www.scientificamerican.com/article/why-are-impact-craters-al/#:~:text=In%20the%20case%20of%20astronomical,craters,%20just%20as%20is%20observed. |access-date=2025-04-18 |website=Scientific American |language=en}}

After impact cratering, volcanism is the most dominant process that has modified the lunar crust. Much of this modification has been preserved due to the lack of plate tectonics on the Moon, such that the lunar surface has changed insignificantly throughout the Moon's geological history. Lunar volcanism has mostly been confined to the near side of the Moon where basaltic lava plains are the dominant volcanic feature.{{cite magazine|last1=Chauhan|first1=Mamta|last2=Saran|first2=Sriram|last3=Bhattacharya|first3=Satadru|last4=Chauhan|first4=Prakash|title=Silicic Caldera: A Phenomenon of rare explosive volcanism on the Moon|magazine=Planetary Sciences and Exploration Programme (PLANEX) Newsletter|publisher=Physical Research Laboratory|volume=5|issue=3|year=2015|page=12|issn=2320-7108}} In contrast, positive topographic features such as domes, cones and shields represent only a tiny fraction of the lunar volcanic record. Volcanoes and lava plains have been found on both sides of the Moon.{{cite web|last=Wickman|first=Robert|url=http://volcano.oregonstate.edu/oldroot/volcanoes/planet_volcano/lunar/Overview.html|title=Volcanism on the Moon|work=Volcano World|publisher=Oregon State University|access-date=2020-12-30|archive-date=2021-02-28|archive-url=https://web.archive.org/web/20210228092451/http://volcano.oregonstate.edu/oldroot/volcanoes/planet_volcano/lunar/Overview.html|url-status=dead}}

{{main|Lunar mare}}

File:Oceanus Procellarum (LRO).png and smaller mare, such as Imbrium and Serenitatis, that sit within its ring. Left of the centerline is Procellarum proper.]]

The lunar maria are large basaltic plains that cover more than 15% of the Moon's surface. They are the most obvious volcanic features on the Moon, appearing as dark topographic features when seen with the naked eye. Many tend to cover the floors of large impact basins and are therefore typically circular in outline, with some smaller maria filling the bottoms of impact craters.{{cite web|url=http://volcano.oregonstate.edu/mare|title=Mare|work=Volcano World|date=4 January 2012 |publisher=Oregon State University|access-date=2020-12-30}} The major lunar maria range in size from more than {{Convert|200|km|mi|abbr=on}} to about {{Convert|1400|km|mi|abbr=on}} and are outclassed only by the larger Oceanus Procellarum, which has a diameter of roughly {{Convert|2590|km|mi|abbr=on}}.{{cite web|title=Oceanus Procellarum|publisher=Astrogeology Science Center|work=Gazetteer of Planetary Nomenclature|url=https://planetarynames.wr.usgs.gov/Feature/4395?__fsk=-308962148|access-date=2020-12-26}}{{cite web|title=Moon Mare/Maria|publisher=USGS Astrogeology|work=Gazetteer of Planetary Nomenclature|url=http://planetarynames.wr.usgs.gov/SearchResults?target=MOON&featureType=Mare%2C%20maria|access-date=2020-12-26}} They typically range in thickness from about {{Convert|500|to|1500|m|ft|abbr=on}}, with individual lava flows ranging from {{Convert|10|to|20|m|ft|abbr=on}} thick. This suggests that each mare is the product of several overlapping eruptive events.

The ages of the mare basalts have been determined both by direct radiometric dating and by the technique of crater counting. The radiometric ages range from about 3.16 to 4.2 billion years, whereas the youngest ages determined from crater counting are about 1.2 billion years.{{cite journal|last1=Papike|first1=James J.|last2=Ryder|first2=Graham|last3=Shearer|first3=Charles K.|title=Lunar Samples|journal=Reviews in Mineralogy and Geochemistry|volume=36|issue=1|pages=5.1–5.234|year=1998}}{{cite journal|last1=Hiesinger|first1=H.|last2=Head|first2=J. W.|last3=Wolf|first3=U.|last4=Jaumann|first4=R.|last5=Neukum|first5=G.|title=Ages and stratigraphy of mare basalts in Oceanus Procellarum, Mare Numbium, Mare Cognitum, and Mare Insularum|journal=Journal of Geophysical Research|volume= 108|issue=E7|page= 5065|year=2003|doi=10.1029/2002JE001985|bibcode=2003JGRE..108.5065H|s2cid=9570915|doi-access= free}} Nevertheless, the majority of mare basalts appear to have erupted between about 3 and 3.5 billion years ago.{{cite book|last=Bansal|first=Malti|title=Now We Set to Settle on Moon Chandrayaan Discovery Paves the Way|chapter=Moon: Geographical Features|publisher=Readworthy Press Corporation|year=2020|isbn=978-93-5018-418-9}} The few basaltic eruptions that occurred on the far side of the Moon are old, whereas the youngest flows are found within Oceanus Procellarum on the near side. While many of the basalts either erupted within, or flowed into, low-lying impact basins, the largest expanse of volcanic units, Oceanus Procellarum, does not correspond to any known impact basin.

The reason that the mare basalts are predominantly located on the near-side hemisphere of the Moon is still being debated by the scientific community. Based on data obtained from the Lunar Prospector mission, it appears that a large proportion of the Moon's inventory of heat producing elements (in the form of KREEP) is located within the regions of Oceanus Procellarum and the Imbrium basin, a unique geochemical province now referred to as the Procellarum KREEP Terrane.{{cite journal|last1=Wieczorek|first1=Mark A.|last2=Jolliff|first2=Bradley L.|last3=Khan|first3=Amir|last4=Pritchard|first4=Matthew E.|last5=Weiss|first5=Benjamin P.|last6=Williams|first6=James G.|last7=Hood|first7=Lon L.|last8=Righter|first8=Kevin|last9=Neal|first9=Clive R.|last10=Shearer|first10=Charles K.|last11=McCallum|first11=I. Stewart|last12=Tompkins|first12=Stephanie|last13=Hawke|first13=B. Ray|last14=Peterson|first14=Chris|last15=Gillis|first15=Jeffrey J.|last16=Bussey|first16=Ben|title=The constitution and structure of the lunar interior|journal=Reviews in Mineralogy and Geochemistry|publisher=Mineralogical Society of America|volume=60|issue=1|pages=221–364|date=2006|doi=10.2138/rmg.2006.60.3|bibcode=2006RvMG...60..221W|s2cid=130734866}}{{cite web |url= http://www.psrd.hawaii.edu/Aug00/newMoon.html |title= A New Moon for the Twenty-First Century |publisher= Planetary Science Research Discoveries |author= G. Jeffrey Taylor |date= August 31, 2000}}{{cite journal|title=Major lunar crustal terranes|last1=Jolliff|first1=Bradley L.|last2=Gillis|first2=Jeffrey J.|last3=Haskin|first3=Larry A.|last4=Korotev|first4=Randy L.|last5=Wieczorek|first5=Mark L.|journal=Journal of Geophysical Research|date= 2000 |pages= 4197–4216|doi=10.1029/1999je001103 |bibcode=2000JGR...105.4197J|volume=105|issue=E2|url=https://hal.archives-ouvertes.fr/hal-02458514/file/Jolliff%20et%20al%2C%202000.pdf|doi-access=free}} While the enhancement in heat production within the Procellarum KREEP Terrane is most certainly related to the longevity and intensity of volcanism found there, the mechanism by which KREEP became concentrated within this region is not agreed upon.{{cite journal|last1=Shearer|first1=Charles K.|last2=Hess|first2=Paul C.|last3=Wieczorek|first3=Mark A.|last4=Pritchard|first4=Matt E.|last5=Parmentier|first5=E. Mark|last6=Borg|first6=Lars E.|last7=Longhi|first7=John|last8=Elkins-Tanton|first8=Linda T.|last9=Neal|first9=Clive R.|last10=Antonenko|first10=Irene|last11=Canup|first11=Robin M.|author11-link=Robin Canup|last12=Halliday|first12=Alex N.|last13=Grove|first13=Tim L.|last14=Hager|first14=Bradford H.|last15=Lee|first15=D-C.|last16=Wiechert|first16=Uwe|title=Thermal and magmatic evolution of the Moon|journal=Reviews in Mineralogy and Geochemistry|volume= 60|issue=1|pages=365–518|date=2006|doi=10.2138/rmg.2006.60.4|bibcode=2006RvMG...60..365S}}

{{main|List of maria on the Moon}}

File:Mare Moscoviense - Clementine.jpg]]

File:Mare Smythii.jpg]]

{{main|Lunar dome}}

A number of domes and cones are present on the Moon, but such features likely formed differently than those on Earth.{{cite web|url=http://volcano.oregonstate.edu/oldroot/volcanoes/planet_volcano/lunar/cones_domes/Overview.html|title=Cones and Domes|work=Volcanism on the Moon|publisher=Oregon State University|access-date=2020-12-30}} Because gravity on the Moon is only one sixth of that on Earth, lunar volcanism is capable of throwing ejecta much further, leaving little to pile up near the vent. Instead of a volcanic cone, such lunar eruptions should form a broad, thin layer around the vent. On Earth, lava domes form from very viscous, pasty lavas. Basaltic lavas are more liquid and tend to form broad, flat lava flows. On the Moon, most of the domes and cones appear to be made of basalts. As a result, they are unlikely to have formed like Earth domes from thick, non-basaltic lavas. Instead, the lunar domes and cones may mark places where the erupted basalts were just barely molten.

File:Marius Hills (LROC-WAC Nearside mosaic).png]]

File:Mons Rümker (LROC-WAC Nearside mosaic).png, a volcanic complex in Oceanus Procellarum]]

Lunar domes are seldom found in isolation. Instead, they more commonly form in groups throughout the lunar lava plains.{{cite book|last1=Sigurdsson|first1=Haraldur|last2=Houghton|first2=Bruce|last3=McNutt|first3=Steve|last4=Rymer|first4=Hazel|last5=Stix|first5=John|title=The Encyclopedia of Volcanoes|chapter=Volcanism on the Moon|publisher=Elsevier|page=695|year=2015|isbn=978-0-12-385938-9}} A prominent example are the Marius Hills, one of the largest volcanic complexes on the Moon.{{cite journal|last1=Besse|first1=S.|last2=Sunshine|first2=J. M.|last3=Staid|first3=M. I.|last4=Petro|first4=N. E.|last5=Boardman|first5=J. W.|last6=Green|first6=R. O.|last7=Head|first7=J. W.|last8=Isaacson|first8=P. J.|last9=Mustard|first9=J. F.|last10=Pieters|first10=C. M.|title=Compositional variability of the Marius Hills volcanic complex from the Moon Mineralogy Mapper (M³)|journal=Journal of Geophysical Research|publisher=American Geophysical Union|pages=1, 2|volume=116|year=2011|doi=10.1029/2010JE003725|bibcode=2011JGRE..116.0G13B|issn=0148-0227|doi-access=free}} They consist of several cones and domes that occupy the summit of a broad topographic swell, which may be the lunar equivalent of a shield volcano. The complex rises {{Convert|100|to|200|m|ft|abbr=on}} from the surrounding plains and forms a {{Convert|35000|km2|mi2|abbr=on}} lava plateau. A total of 59 cones and 262 domes ranging in diameter from {{Convert|2|to|25|km|mi|abbr=on}} have been identified.

Mons Rümker is a smaller complex similar in appearance to the Marius Hills. It comprises a plateau with an area of roughly {{Convert|2000|km2|mi2|abbr=on}} and rises {{Convert|200|to|1300|m|ft|abbr=on}} above the surrounding surface. Three main basalt units ranging in age from 3.51 to 3.71 billion years have been identified at Mons Rümker, although the youngest volcanic features may be steep-sided domes on the plateau surface as they show indications of having been active until the Eratosthenian. More than 20 domes overlie the plateau and are the most prominent volcanic landforms of Mons Rümker.{{cite journal|last1=Zhao|first1=Jiannan|last2=Xiao|first2=Long|last3=Qiao|first3=Le|last4=D. Glotch|first4=Timothy|last5=Huang|first5=Qian|title=The Mons Rümker volcanic complex of the Moon: Acandidate landing site for the Chang'E-5 mission|journal=Journal of Geophysical Research|publisher=American Geophysical Union|pages=1419, 1420|year=2017|issn=0148-0227}}

The Gruithuisen Domes in northwestern Mare Imbrium consist of two volcanic edifices: Mons Gruithuisen Gamma to the north and Mons Gruithuisen Delta to the south.{{citation|last1=Bruno|first1=B. C.|last2=Lucey|first2=P. G.|last3=Hawke|first3=B. R.|title=High-Resolution UV-Visible Spectroscopy of Lunar Red Spots|journal=Lunar and Planetary Science Conference Proceedings|publisher=Lunar and Planetary Institute|page=409|volume=21|year=1991|bibcode=1991LPSC...21..405B}} They are situated on the rim of an impact crater and differ in color from the surrounding rocks. The domes may mark a rare instance of non-basaltic volcanism on the Moon.{{cite web|url=http://volcano.oregonstate.edu/oldroot/volcanoes/planet_volcano/lunar/cones_domes/gruith.html|title=Gruitheisen Domes|work=Volcano World|publisher=Oregon State University|access-date=2020-12-30}} Mons Hansteen, a roughly triangular-shaped dome on the southern margin of Oceanus Procellerum, is another example of a rare non-basaltic lunar volcano. It consists of high-silica material that was erupted roughly 3.5 to 3.7 billion years ago from vents along northeast, northwest and southwest-trending fractures.{{cite journal|last1=Boyce|first1=Joseph M.|last2=Giguere|first2=Thomas A.|last3=Hawke|first3=B. Ray|last4=Mouginis-Mark|first4=Peter J.|last5=Robinson|first5=Mark S.|last6=Lawrence|first6=Samiel J.|last7=Trang|first7=David|last8=Clegg-Watkins|first8=Ryan|title=Hansteen Mons: An LROC geological perspective|journal=Icarus|publisher=Elsevier|page=254|year=2017|volume=283|doi=10.1016/j.icarus.2016.08.013|bibcode=2017Icar..283..254B|issn=0019-1035|doi-access=free}}

The Compton–Belkovich Volcanic Complex (CBVC) is a {{Convert|25|km|mi|abbr=on}} wide and {{Convert|35|km|mi|abbr=on}} long non-mare feature on the far side of the Moon. It differs from other lunar volcanic features due to its evolved lithology, regional tectonic setting, its location being near the north pole, far from the Procellarum KREEP Terrane and its recent association with endogenic water. In the middle of the CBVC lies an irregular-shaped depression bounded by fault scarps that is believed to be a caldera. Just to the west is a roughly {{Convert|10|km|mi|abbr=on}} wide and {{Convert|18|km|mi|abbr=on}} long feature called West Dome. A volcanic cone-like feature, called East Dome, lies near the eastern caldera margin. It has a more or less north–south trend, measuring {{Convert|12|km|mi|abbr=on}} long and {{Convert|7|km|mi|abbr=on}} wide.{{cite journal|last1=Chauhan|first1=M.|last2=Bhattacharya|first2=S.|last3=Saran|first3=S.|last4=Chauhan|first4=P.|last5=Dagar|first5=A.|title=Compton–Belkovich Volcanic Complex (CBVC): An ash flow caldera on the Moon|journal=Icarus|publisher=Elsevier|pages=116, 117, 118|year=2015|volume=253|doi=10.1016/j.icarus.2015.02.024|bibcode=2015Icar..253..115C|issn=0019-1035}} Just north of the caldera is a feature called Little Dome, {{convert|500|m|ft|abbr=on}} in diameter. Further north is an elongated dome, oriented north–south, called Middle Dome. It is {{convert|2.5|km|mi|abbr=on}} long and {{convert|0.6|km|mi|abbr=on}} wide. Both Little Dome and Middle Dome have boulders on top that may be volcanic blocks.{{cite conference|url=http://www.lpi.usra.edu/meetings/lpsc2011/pdf/2224.pdf|conference=42nd Lunar and Planetary Science Conference |title=Compton-Belkovich: Nonmare, Silicic Volcanism on the Moon's Far Side|last1=Jolliff|first1=B. L.|first2=T. N. |last2=Tran |first3=S. J. |last3=Lawrence |first4=M. S. |last4=Robinson |year=2011|access-date=2020-12-30 }} Big Dome, also known as North Dome, is further to the north at the edge of the CBVC. It is {{convert|2.5|km|mi|abbr=on}} in diameter with a depression in the top. Small-crater size frequency distribution has given inconclusive results for the timing of CBVC volcanism, with ages ranging from less than 1 billion years to greater than 3 billion years.{{cite conference|url=https://www.lpi.usra.edu/meetings/lpsc2013/pdf/2469.pdf|conference=44th Lunar and Planetary Science Conference |title=Crater Size-Frequency Distribution Measurements and Age of the Compton-Belkovich Volcanic Complex|last1=Shirley|first1=K. A.|last2=Zanetti|first2=M.|last3=Jolliff|first3=B.|last4=van der Bogert|first4=C. H.|last5=Hiesinger|first5=H.|year=2013|access-date=2020-12-30}}

{{main|Lunar lava tube}}

File:Mare Tranquillitatis pit crater.jpg may be the partial collapse of a lunar lava tube]]

Although lava tubes have long been known to exist on Earth, it has only been relatively recently that they have been confirmed to also exist on the Moon. Their existence is sometimes revealed by the presence of a "skylight", a place in which the roof of the tube has collapsed, leaving a circular hole that can be observed by lunar orbiters.{{citation |last1=Huber |first1=S. A. |last2=Hendrickson |first2=D. B. |last3=Jones |first3=H. L. |last4=Thornton |first4=J. P. |last5=Whittaker |first5=W. L. |last6=Wong |first6=U. Y. |contribution=Astrobotic Technology: Planetary Pits and Caves for Science and Exploration |display-authors=1 |date=2014 |postscript=. |title=Annual Meeting of the Lunar Exploration Analysis Group, abstract 3065 |url=http://www.hou.usra.edu/meetings/leag2014/pdf/3065.pdf |access-date=24 January 2016 }}{{citation|first=Liat |last=Clark |date=9 February 2011 |title=First underground cave photographed on the moon |url=https://www.wired.co.uk/news/archive/2011-02/09/lunar-cave-photos |publisher=Wired UK |access-date=24 January 2016 |archive-url=https://web.archive.org/web/20110210183928/http://www.wired.co.uk/news/archive/2011-02/09/lunar-cave-photos |archive-date=10 February 2011 |url-status=dead }} An area displaying a lava tube is the Marius Hills region.{{citation |title=Lava Tubes and Channels in the Lunar Marius Hills |last=Greeley |first=Ronald |date=December 1971 |journal=The Moon |volume=3 |issue=3 |pages=289–314 |doi=10.1007/BF00561842 |bibcode=1971Moon....3..289G |hdl=2060/19710008532 |s2cid=122121114 |hdl-access=free }} In 2008, an opening to a lava tube in this area may have been discovered by the Japanese Kaguya spacecraft.{{citation |first=Brian |last=Handwerk |date=October 26, 2009 |title=First Moon "Skylight" Found – Could House Lunar Base? |publisher=National Geographic |url=http://news.nationalgeographic.com/news/2009/10/091026-moon-skylight-lunar-base.html |archive-url=https://web.archive.org/web/20091029035007/http://news.nationalgeographic.com/news/2009/10/091026-moon-skylight-lunar-base.html |url-status=dead |archive-date=October 29, 2009 |access-date=2011-01-27 }} The skylight was photographed in more detail in 2011 by NASA's Lunar Reconnaissance Orbiter, showing both the 65-meter-wide pit and the floor of the pit about {{Convert|36|m|ft|abbr=on}} below.{{cite web |title=The Marius Hills hole is a possible skylight|url=http://photojournal.jpl.nasa.gov/catalog/PIA12954|work=Photojournal|publisher=Jet Propulsion Laboratory|access-date=28 June 2011}} In 2023–2024, radar imaging of the Mare Tranquillitatis pit crater from NASA's Lunar Reconnaissance Orbiter was analyzed and determined to have been formed by the collapse of a lava tube that resulted in the formation of a cave conduit at least tens of meters long, proving the existence of lunar caves.{{Cite journal |last=Carrer |first=Leonardo |last2=Pozzobon |first2=Riccardo |last3=Sauro |first3=Francesco |last4=Castelletti |first4=Davide |last5=Patterson |first5=Gerald Wesley |last6=Bruzzone |first6=Lorenzo |date=2024-07-15 |title=Radar evidence of an accessible cave conduit on the Moon below the Mare Tranquillitatis pit |url=https://www.nature.com/articles/s41550-024-02302-y |journal=Nature Astronomy |language=en |pages=1–8 |doi=10.1038/s41550-024-02302-y |issn=2397-3366|url-access=subscription }} There may also be lava tubes in the Mare Serenitatis.{{citation |contribution=A search for intact lava tubes on the Moon: Possible lunar base habitats |last1=Coombs |first1=Cassandra R. |last2=Hawke |first2=B. Ray |title=In NASA. Johnson Space Center, The Second Conference on Lunar Bases and Space Activities of the 21st Century (SEE N93-17414 05-91) |volume=1 |pages=219–229 |date=September 1992 |bibcode=1992lbsa.conf..219C }}{{citation |title=Scientists eye moon colonies — in the holes on the lunar surface |url=http://articles.nydailynews.com/2010-01-04/news/17943312_1_lava-lunar-surface-moon |work=New York Daily News |access-date=13 October 2011 |archive-date=2011-07-14 |archive-url=https://web.archive.org/web/20110714223229/http://articles.nydailynews.com/2010-01-04/news/17943312_1_lava-lunar-surface-moon |url-status=dead }}

Lunar lava tubes may potentially serve as enclosures for human habitats.{{citation |first1=Ian |last1=O'Neill |date=October 27, 2009 |title=Living in Lunar Lava Tubes |work=Discover News |url=http://news.discovery.com/space/moon-lunar-lava-skylight.html |access-date=1 January 2012 |archive-date=23 October 2012 |archive-url=https://web.archive.org/web/20121023152520/http://news.discovery.com/space/moon-lunar-lava-skylight.html |url-status=dead }} Tunnels larger than {{convert|300|m|ft|abbr=on}} in diameter may exist, lying under {{convert|40|m|ft|abbr=on}} or more of basalt, with a stable temperature of {{convert|-20|C|F}}.{{citation |display-authors=1 |last1=York |first1=Cheryl Lynn |last2=Walden |first2=Bryce |last3=Billings |first3=Thomas L. |last4=Reeder |first4=P. Douglas |contribution=Lunar lava tube sensing |title=Lunar and Planetary Institute, Joint Workshop on New Technologies for Lunar Resource Assessment |pages=51–52 |date=December 1992 |bibcode=1992ntlr.work...51Y }} These natural tunnels provide protection from cosmic radiation, solar radiation, meteorites, micrometeorites, and ejecta from impacts. They are insulated from the extreme temperature variations on the lunar surface and could provide a stable environment for inhabitants.{{citation |display-authors=1 |last1=De Angelis |first1=G. |last2=Wilson |first2=J. W. |last3=Clowdsley |first3=M. S. |last4=Nealy |first4=J. E. |last5=Humes |first5=D. H. |last6=Clem |first6=J. M. |title=Lunar Lava Tubes Radiation Safety Analysis |journal=Bulletin of the American Astronomical Society |volume=33 |page=1037 |date=November 2001 |bibcode=2001DPS....33.1003D }}

File:Apollo 17 orange soil.jpg soil discovered on the Apollo 17 mission. The orange color is due to microscopic glass beads created by volcanic processes earlier in the Moon's history.]]

Near the edges of the lunar mare are dark layers of material that cover many thousands of square kilometers. They contain many small spheres of orange and black glass that probably formed from small drops of lava that cooled very quickly. Such droplets are believed to be ejecta from lava fountain eruptions that were larger than those on Earth.{{cite web|last=Wickman|first=Robert|url=http://volcano.oregonstate.edu/oldroot/volcanoes/planet_volcano/lunar/Dk_Mantles/Overview.html|title=Dark Mantling Deposits|work=Volcanism on the Moon|publisher=Oregon State University|access-date=2020-12-30}} The largest known deposits occur at Taurus–Littrow, Sinus Aestuum, Sulpicius Gallus, Rima Bode, Mare Vaporum, Mare Humorum and the Aristarchus plateau in the central near side of the Moon.{{cite web|url=http://volcano.oregonstate.edu/oldroot/volcanoes/planet_volcano/lunar/Dk_Mantles/dk_map.html|title=Map of Large Dark Mantling Deposits|work=Volcano World|publisher=Oregon State University|access-date=2020-12-30}}

Many smaller pyroclastic deposits measure only a few kilometers in diameter and are almost always located near the mare or in large impact crater floors, although several also lie along clear fault lines. They were likely produced by small volcanic explosions since most contain a small elongated or irregular-shaped central pit or crater.{{cite web|url=http://volcano.oregonstate.edu/oldroot/volcanoes/planet_volcano/lunar/Dk_Mantles/crater.html|title=Crater Alphonsus|work=Volcano World|publisher=Oregon State University|access-date=2020-12-30}} Examples are preserved along the crater floor edge of Alphonsus, an impact crater on the eastern edge of Mare Nubium.

Extending about {{Convert|7|km|mi|abbr=on}} east-southeast from the CBVC is a highly reflective area that may be a pyroclastic flow deposit. Its reflectivity is stronger in the {{Convert|7.1|to|7.|μm|abbr=on}} range, indicating that quartz or alkali feldspar is the major constituent. Explosive remains also appear scattered to the east for about {{Convert|300|km|mi|abbr=on}}, covering an area of {{Convert|70000|km2|mi2|abbr=on}}. The large extent of this pyroclastic deposit is due to the Moon's low gravity, such that a giant explosive eruption from the CBVC was able to spread debris over an area much greater than would be possible on Earth.{{cite web|author1=Durham University|title=Extent of Moon's giant volcanic eruption is revealed|url=http://phys.org/news/2015-03-extent-moon-giant-volcanic-eruption.html|publisher=PhysOrg|access-date=8 January 2021|date=18 March 2015}}

{{main|Rille}}

These are long, narrow depressions in the lunar surface that resemble channels. Their precise formation remains to be determined, but they were likely formed by different processes. For instance, sinuous rilles meander in a curved path like a mature river and are thought to represent lava channels or the remains of collapsed lava tubes.{{cite web|last=Wickman|first=Robert|url=http://volcano.oregonstate.edu/oldroot/volcanoes/planet_volcano/lunar/sin_rilles/Overview.html|title=Sinuous Rilles|work=Volcanism on the Moon|publisher=Oregon State University|access-date=2020-12-30}} They normally extend from small pit structures that are believed to have been volcanic vents.{{cite web|url=http://volcano.oregonstate.edu/oldroot/volcanoes/planet_volcano/lunar/sin_rilles/schr_v1.html|title=Schroter's Valley 1|work=Volcano World|publisher=Oregon State University|access-date=2020-12-30}} Schroter's Valley between Mare Imbrium and Oceanus Procellarum is the largest sinuous rille. Another prominent example is Rima Hadley, which formed nearly 3.3 billion years ago.{{cite web|url=http://volcano.oregonstate.edu/oldroot/volcanoes/planet_volcano/lunar/sin_rilles/hadl_orbit.html|title=Hadley Rille (from Orbit)|work=Volcano World|publisher=Oregon State University|access-date=2020-12-30}}

Arcuate rilles have a smooth curve and are found on the edges of the dark lunar maria. They are believed to have formed when the lava flows that created a mare cooled, contracted and sank.{{cite book|last=T. Wlasuk|first=Peter|title=Observing the Moon|publisher=Springer Science+Business Media|chapter=The Lunar Rilles|page=22|year=2000|isbn=1-85233-193-3}} These are found all over the Moon; prominent examples can be seen near the southwestern border of Mare Tranquillitatis and on the western southeastern border of Mare Humorum.{{cite book|last=Grego|first=Peter|title=The Moon and How to Observe It|publisher=Springer Science+Business Media|chapter=Faults and Linear Rilles|page=32|year=2005|isbn=1-85233-748-6}}

Analysis of Moon magma samples retrieved by the Apollo missions indicate that volcanism on the Moon produced a relatively thick lunar atmosphere for a period of 70 million years between 3 and 4 billion years ago. This atmosphere, sourced from gases ejected from lunar volcanic eruptions, was twice the thickness of that of present-day Mars. It has been theorized, in fact, that this ancient atmosphere could have supported life, though no evidence of life has been found.{{cite news|title=Life on the Moon? New study argued life could have existed on the lunar surface|last=Ciaccia|first=Chris|newspaper=Fox News|url=https://www.foxnews.com/science/life-on-the-moon-new-study-argued-life-could-have-existed-on-the-lunar-surface/|year=2018|access-date=2020-12-19}} The ancient lunar atmosphere was eventually stripped away by solar winds and dissipated into space.{{cite magazine|last=John|first=Tara|url=https://time.com/4974580/nasa-moon-had-atmosphere-volcanoes/|title=NASA: The Moon Once Had an Atmosphere That Faded Away|magazine=Time|year=2017|access-date=2020-12-19}}

Partial melting of the lunar mantle and the emplacement of Oceanus Procellarum flood basalts may have caused axial tilting of the Moon 3 billion years ago, during which time the lunar poles shifted {{Convert|125|mi|km|abbr=on}} to their modern positions. This polar wander is inferred from polar hydrogen deposits that are antipodal and displaced equally from each pole along opposite longitudes.{{cite web|last=Lewis|first=Danny|title=Ancient Volcanoes May Have Shifted the Moon's Poles|url=https://www.smithsonianmag.com/smart-news/ancient-volcanoes-may-have-shifted-moons-poles-180958562/|website=Smithsonian Magazine|year=2016|access-date=2020-12-19}}

In 2014, NASA announced "widespread evidence of young lunar volcanism" at 70 irregular mare patches identified by the Lunar Reconnaissance Orbiter, some less than 50 million years old. This raises the possibility of a much warmer lunar mantle than previously estimated, at least on the near side where the deep crust is substantially warmer because of the greater concentration of radioactive elements.{{cite web |url=http://news.discovery.com/space/imps-reveal-volcanoes-erupted-recently-on-the-moon-141014.htm |title=Volcanoes Erupted 'Recently' on the Moon |publisher=Discovery News |date=14 October 2014 |author=Jason Major |url-status=live |archive-url=https://web.archive.org/web/20141016190653/http://news.discovery.com/space/imps-reveal-volcanoes-erupted-recently-on-the-moon-141014.htm |archive-date=16 October 2014}}{{cite web |url=http://www.nasa.gov/press/2014/october/nasa-mission-finds-widespread-evidence-of-young-lunar-volcanism/#.VDxNw0t3uxo |title=NASA Mission Finds Widespread Evidence of Young Lunar Volcanism |publisher=NASA |date=12 October 2014 |url-status=live |archive-url=https://web.archive.org/web/20150103095208/http://www.nasa.gov/press/2014/october/nasa-mission-finds-widespread-evidence-of-young-lunar-volcanism/#.VDxNw0t3uxo |archive-date=3 January 2015}}{{cite journal |url=https://www.science.org/content/article/recent-volcanic-eruptions-moon |title=Recent volcanic eruptions on the moon |journal=Science |date=12 October 2014 |author=Eric Hand |url-status=live |archive-url=https://web.archive.org/web/20141014092239/http://news.sciencemag.org/space/2014/10/recent-volcanic-eruptions-moon |archive-date=14 October 2014}}{{cite journal |title=Evidence for basaltic volcanism on the Moon within the past 100 million years |journal=Nature Geoscience |last1=Braden |first1=S.E. |last2=Stopar |first2=J.D. |last3=Robinson |first3=M.S. |last4=Lawrence |first4=S.J. |last5=van der Bogert |first5=C.H. |last6=Hiesinger |first6=H. |volume=7 |issue=11 |pages=787–791 |bibcode=2014NatGe...7..787B |doi=10.1038/ngeo2252 |year=2014}} Just prior to this, evidence has been presented for 2–10 million years younger basaltic volcanism inside the crater Lowell,{{cite journal |last1=Srivastava |first1=N. |last2=Gupta |first2=R.P. |year=2013 |title=Young viscous flows in the Lowell crater of Orientale basin, Moon: Impact melts or volcanic eruptions? |journal=Planetary and Space Science |volume=87 |pages=37–45 |doi=10.1016/j.pss.2013.09.001 |bibcode=2013P&SS...87...37S}}{{cite journal |last1=Gupta |first1=R.P. |last2=Srivastava |first2=N. |last3=Tiwari |first3=R.K. |year=2014 |title=Evidences of relatively new volcanic flows on the Moon |journal=Current Science |volume=107 |issue=3 |pages=454–460}} located in the transition zone between the near and far sides of the Moon. An initially hotter mantle and/or local enrichment of heat-producing elements in the mantle could be responsible for prolonged activities also on the far side in the Orientale basin.{{cite journal |last1=Whitten |first1=J. |display-authors=etal |year=2011 |title=Lunar mare deposits associated with the Orientale impact basin: New insights into mineralogy, history, mode of emplacement, and relation to Orientale Basin evolution from Moon Mineralogy Mapper (M3) data from Chandrayaan-1 |journal=Journal of Geophysical Research |volume=116 |page=E00G09 |doi=10.1029/2010JE003736 |bibcode=2011JGRE..116.0G09W |s2cid=7234547|doi-access=free }}{{cite journal|last1=Cho |first1=Y.|display-authors=etal|year=2012|title=Young mare volcanism in the Orientale region contemporary with the Procellarum KREEP Terrane (PKT) volcanism peak period 2 b.y. ago|journal=Geophysical Research Letters|volume=39|issue=11|page=L11203|bibcode=2012GeoRL..3911203C|doi=10.1029/2012GL051838|s2cid=134074700 }} There are currently no active volcanoes on the Moon, although moonquake data published in 2012 suggest that there is a substantial amount of magma under the lunar surface. The lack of active volcanism on the Moon may be due to the magma being too dense to rise to the surface.{{cite magazine|last=Solon|first=Olivia|url=https://www.wired.co.uk/article/moon-volcanoes|title=Why the Moon has no active volcanoes|magazine=Wired UK|year=2012|access-date=2021-01-04}}

{{Portal|Volcanoes|Solar System}}

• List of extraterrestrial volcanoes
• Geology of the Moon
• Lunar magma ocean
• Volcanism on Io

{{reflist}}

{{The Moon}}

Category:Pre-Nectarian

Category:Nectarian

Category:Imbrian

Category:Eratosthenian