Editing Volcano (section)

===Dormant and reactivated{{anchor|Dormant}}===
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[[File:Narcondam island.jpg|thumb|[[Narcondam Island]], India, is classified as a dormant volcano by the [[Geological Survey of India]].]]
The USGS defines a dormant volcano as any volcano that is not showing any signs of unrest such as earthquake swarms, ground swelling, or excessive noxious gas emissions, but which shows signs that it could yet become active again.<ref name="activity_levels" /> Many dormant volcanoes have not erupted for thousands of years, but have still shown signs that they may be likely to erupt again in the future.<ref name="Nelson2016">{{cite web|url=http://www.tulane.edu/~sanelson/Natural_Disasters/volhaz&pred.htm|title=Volcanic Hazards & Prediction of Volcanic Eruptions|publisher=Tulane University|date=October 4, 2016|access-date=September 5, 2018|last=Nelson|first=Stephen A.}}</ref><ref name="VolcWorldDormant">{{cite web|url=http://volcano.oregonstate.edu/how-volcano-defined-being-active-dormant-or-extinct|title=How is a volcano defined as being active, dormant, or extinct?|work=Volcano World|publisher=Oregon State University|access-date=September 5, 2018|archive-date=January 12, 2013|archive-url=https://web.archive.org/web/20130112014631/http://volcano.oregonstate.edu/how-volcano-defined-being-active-dormant-or-extinct|url-status=dead}}</ref>

In an article justifying the re-classification of Alaska's [[Mount Edgecumbe (Alaska)|Mount Edgecumbe]] volcano from "dormant" to "active", volcanologists at the [[Alaska Volcano Observatory]] pointed out that the term "dormant" in reference to volcanoes has been deprecated over the past few decades and that "[t]he term "dormant volcano" is so little used and undefined in modern volcanology that the Encyclopedia of Volcanoes (2000) does not contain it in the glossaries or index",<ref>{{cite web|url=https://www.avo.alaska.edu/news.php?id=1576|title=Mount Edgecumbe volcanic field changes from 'dormant' to 'active' -- what does that mean?|author=<!--Not stated-->|date=May 9, 2022|publisher=Alaska Volcano Observatory|access-date=June 2, 2022}}</ref> however the USGS still widely employs the term.

Previously a volcano was often considered to be extinct if there were no written records of its activity. Such a generalization is inconsistent with observation and deeper study, as has occurred recently with the unexpected eruption of the [[Chaitén (volcano)|Chaitén volcano]] in 2008.<ref name=Castro2009>{{cite journal|last1=Castro|first1=J.|last2=Dingwell|first2=D.|title=Rapid ascent of rhyolitic magma at Chaitén volcano, Chile|journal=Nature|volume=461|pages=780–783|year=2009|issue=7265|doi=10.1038/nature08458|pmid=19812671|bibcode=2009Natur.461..780C|s2cid=4339493}}</ref> Modern volcanic activity monitoring techniques, and improvements in the modelling of the factors that produce eruptions, have helped the understanding of why volcanoes may remain dormant for a long time, and then become unexpectedly active again. The potential for eruptions, and their style, depend mainly upon the state of the magma storage system under the volcano, the eruption trigger mechanism and its timescale.<ref name="Cserép2023">{{cite journal|last1=Cserép|first1=B.|last2=Szemerédi|first2=M.|last3=Harangi|first3=S.|last4=Erdmann|first4=S.|last5=Bachmann|first5=O.|last6=Dunkl|first6=I.|last7=Seghedi|first7=I.|last8=Mészáros|first8=K.|last9=Kovács|first9=Z.|last10 =Virág| first10=A|last11=Ntaflos|first11=T.|title=Constraints on the pre-eruptive magma storage conditions and magma evolution of the 56–30 ka explosive volcanism of Ciomadul (East Carpathians, Romania)|journal=Contribribtions to Mineralogy and Petrology|volume=178|issue=96|year=2023|doi=10.1007/s00410-023-02075-z|bibcode=2023CoMP..178...96C|doi-access=free|hdl=20.500.11850/646219|hdl-access=free}}</ref>{{rp|95}} For example, the [[Yellowstone Caldera|Yellowstone]] volcano has a repose/recharge period of around 700,000 years, and [[Toba Lake|Toba]] of around 380,000 years.<ref name="chesner1991">{{cite journal|doi=10.1130/0091-7613(1991)019<0200:EHOESL>2.3.CO;2|url=http://www.geo.mtu.edu/~raman/papers/ChesnerGeology.pdf|last1=Chesner|first1=C.A.|last2=Rose|first2=J.A.|last3=Deino|first3=W.I.|last4=Drake|first4=R.|last5=Westgate|first5=A.|title=Eruptive History of Earth's Largest Quaternary caldera (Toba, Indonesia) Clarified|volume=19|pages=200–203|journal=Geology|date=March 1991|access-date=January 20, 2010|issue=3|bibcode=1991Geo....19..200C}}</ref> [[Vesuvius]] was described by Roman writers as having been covered with gardens and vineyards before its unexpected [[Eruption of Mount Vesuvius in 79|eruption of 79 CE]], which destroyed the towns of [[Herculaneum]] and [[Pompeii]].

Accordingly, it can sometimes be difficult to distinguish between an extinct volcano and a dormant (inactive) one. Long volcano dormancy is known to decrease awareness.<ref name="Cserép2023"/>{{rp|96}} [[Pinatubo]] was an inconspicuous volcano, unknown to most people in the surrounding areas, and initially not seismically monitored before its unanticipated and catastrophic eruption of 1991. Two other examples of volcanoes that were once thought to be extinct, before springing back into eruptive activity were the long-dormant [[Soufrière Hills]] volcano on the island of [[Montserrat]], thought to be extinct until activity resumed in 1995 (turning its capital [[Plymouth, Montserrat|Plymouth]] into a [[ghost town]]) and [[Fourpeaked Mountain]] in Alaska, which, before its September 2006 eruption, had not erupted since before 8000 BCE.