Editing Venus (section)

==== Volcanism ====
{{Main|Volcanism on Venus}}
[[Image:PIA00084 Eistla region pancake volcanoes.jpg|thumb|left|upright=1.1|Radar mosaic of two [[pancake dome]]s in Venus's Eistla region—both {{Convert|65|km|mi|abbr=on}} wide and less than {{Convert|1|km|mi|abbr=on}} high]]

Much of the Venusian surface appears to have been shaped by volcanic activity. Venus has several times as many volcanoes as Earth, and it has 167 large volcanoes that are over {{convert|100|km|mi|sigfig=1|abbr=on}} across. The only volcanic complex of this size on Earth is the [[Hawaii (island)|Big Island]] of Hawaii.<ref name="Frankel" />{{rp|154}} More than 85,000 volcanoes on Venus have been identified and mapped.<ref>{{cite web |title=A new catalog pinpoints volcanic cones in the best available surface images of Venus – those gathered 30 years ago by NASA's Magellan spacecraft. |url=https://skyandtelescope.org/astronomy-news/85000-volcanoes-mapped-on-venus |website=skyandtelescope.org |date=14 April 2023 |access-date=16 April 2023 |archive-date=16 April 2023 |archive-url=https://web.archive.org/web/20230416223821/https://skyandtelescope.org/astronomy-news/85000-volcanoes-mapped-on-venus/ |url-status=live }}</ref><ref>{{cite journal |last1=Hahn |first1=Rebecca M. |last2=Byrne |first2=Paul K. |title=A Morphological and Spatial Analysis of Volcanoes on Venus |journal=Journal of Geophysical Research: Planets |date=April 2023 |volume=128 |issue=4 |pages=e2023JE007753 |doi=10.1029/2023JE007753 |bibcode=2023JGRE..12807753H |s2cid=257745255 |quote=With the Magellan synthetic-aperture radar full-resolution radar map left- and right-look global mosaics at 75 m-per-pixel resolution, we developed a global catalogue of volcanoes on Venus that contains ~85,000 edifices, ~99% of which are <5 km in diameter. We find that Venus hosts far more volcanoes than previously mapped, and that although they are distributed across virtually the entire planet, size–frequency distribution analysis reveals a relative lack of edifices in the 20–100 km diameter range, which could be related to magma availability and eruption rate.}}</ref> This is not because Venus is more volcanically active than Earth, but because its crust is older and is not subject to the [[erosion]] processes active on Earth. Earth's [[oceanic crust]] is continually recycled by [[subduction]] at the boundaries of tectonic plates, and has an average age of about 100 million years,<ref name=Karttunen_et_al_2007/> whereas the Venusian surface is estimated to be 300–600{{spaces}}million years old.<ref name="Nimmo98" /><ref name="Frankel" />

Several lines of evidence point to ongoing [[volcanic]] activity on Venus. Sulfur dioxide concentrations in the upper atmosphere dropped by a factor of 10 between 1978 and 1986, jumped in 2006, and again declined 10-fold.<ref name="ESA_2012-12-03"/> This may mean that levels were boosted several times by large volcanic eruptions.<ref name=Glaze_1999/><ref name="Marcq2012"/> It has been suggested that Venusian lightning (discussed below) could originate from volcanic activity (i.e. [[volcanic lightning]]). In January 2020, astronomers reported evidence suggesting that Venus is currently volcanically active, specifically the detection of [[olivine]], a volcanic product that would weather quickly on the planet's surface.<ref name="NYT-20200109"/><ref name="SCI-20200103"/>

This massive volcanic activity is fuelled by a hot interior, which models say could be explained by energetic collisions when the planet was young, as well as [[radioactive decay]] as in the case of the earth. Impacts would have had significantly higher velocity than on Earth, both because Venus moves faster due to its closer proximity to the Sun and because high-eccentricity objects colliding with the planet would have high speeds.<ref>{{Cite web |url=https://www.sci.news/space/venus-volcanism-12114.html |title=Early, Energetic Collisions Could Have Fueled Venus Volcanism: Study {{!}} Sci.News |date=20 July 2023 |access-date=21 July 2023 |archive-date=21 July 2023 |archive-url=https://web.archive.org/web/20230721193015/https://www.sci.news/space/venus-volcanism-12114.html |url-status=live }}</ref>

In 2008 and 2009, the first direct evidence for ongoing volcanism was observed by ''Venus Express'', in the form of four transient localized infrared hot spots within the rift zone [[Ganis Chasma]],<ref name="USGS_Ganis_Chasma"/>{{refn|group=note|Misstated as "Ganiki Chasma" in the press release and scientific publication.<ref name = "Lakdawalla2015"/>}} near the shield volcano [[Maat Mons]]. Three of the spots were observed in more than one successive orbit. These spots are thought to represent lava freshly released by volcanic eruptions.<ref name="Lakdawalla2015"/><ref name="ESA_2015-06-18"/> The actual temperatures are not known, because the size of the hot spots could not be measured, but are likely to have been in the {{convert|800|-|1100|K|C F}} range, relative to a normal temperature of {{convert|740|K|C F}}.<ref name="Shalygin2015"/> In 2023, scientists reexamined topographical images of the Maat Mons region taken by the ''[[Magellan (spacecraft)|Magellan]]'' orbiter. Using computer simulations, they determined that the topography had changed during an 8-month interval, and concluded that active volcanism was the cause.<ref>{{cite web | title=Why the Discovery of an Active Volcano on Venus Matters | last=Kluger | first=Jeffrey | url=https://time.com/6264160/why-volcanoes-on-venus-matter/ | publisher=[[Time (magazine)|Time]] | date=17 March 2023 | access-date=19 March 2023 | archive-date=19 March 2023 | archive-url=https://web.archive.org/web/20230319022005/https://time.com/6264160/why-volcanoes-on-venus-matter/ | url-status=live }}</ref>