Editing Pyroclastic flow (section)

===Interaction with water===
Testimonial evidence from the [[1883 eruption of Krakatoa]], supported by experimental evidence,<ref name=Freundt2003>{{cite journal
  | title = Entrance of hot pyroclastic flows into the sea: experimental observations
  | journal = [[Bulletin of Volcanology]] 
  | volume = 65
  | pages = 144–164
  | year = 2003
  | bibcode = 2002BVol...65..144F
  | last1 = Freundt
  | first1 = Armin
  | issue = 2 
 | doi = 10.1007/s00445-002-0250-1| s2cid = 73620085 
 }}</ref> shows that pyroclastic flows can cross significant bodies of water. However, that might be a [[pyroclastic surge]], not flow, because the density of a gravity current means it cannot move across the surface of water.<ref name=Freundt2003/> One flow reached the [[Sumatra]]n coast as far as {{convert|48|km|nmi|frac=2|abbr=off}} away.<ref>Camp, Vic. "KRAKATAU, INDONESIA (1883)". How Volcanoes Work. Department of Geological Sciences, San Diego State University, 31 Mar. 2006. Web. 15 Oct. 2010. [http://www.geology.sdsu.edu/how_volcanoes_work/Krakatau.html] {{Webarchive|url=https://web.archive.org/web/20141216203501/http://www.geology.sdsu.edu/how_volcanoes_work/Krakatau.html|date=2014-12-16}}.</ref>

A 2006 BBC documentary film, ''Ten Things You Didn't Know About Volcanoes'',<ref>{{IMDb title|qid=Q130302251|id=tt1027751|title=Ten Things You Didn't Know About Volcanoes (2006)}}</ref> demonstrated tests by a research team at [[Kiel University]], Germany, of pyroclastic flows moving over the water.<ref>[http://cat.inist.fr/?aModele=afficheN&cpsidt=14575991 Entrance of hot pyroclastic flows into the sea: experimental observations], [[INIST]].</ref> When the reconstructed pyroclastic flow (stream of mostly hot ash with varying densities) hit the water, two things happened: the heavier material fell into the water, precipitating out from the pyroclastic flow and into the liquid; the temperature of the ash caused the water to evaporate, propelling the pyroclastic flow (now only consisting of the lighter material) along on a bed of steam at an even faster pace than before.

During some phases of the Soufriere Hills volcano on Montserrat, pyroclastic flows were filmed about {{convert|1|km|nmi|frac=2|abbr=on}} offshore. These show the water boiling as the flow passes over it. The flows eventually built a delta, which covered about {{convert|1|km2|acre|sigfig=2|abbr=on}}. Another example was observed in 2019 at [[Stromboli]] when a pyroclastic flow traveled for several hundreds of meters above the sea.<ref>{{Cite web|first1=Sandro|last1=de Vita|first2=Mauro A.|last2=Di Vito|first3=Rosella|last3=Nave|date=2019-09-05|title=Quando un flusso piroclastico scorre sul mare: esempi a Stromboli e altri vulcani|url=https://ingvvulcani.com/2019/09/05/quando-un-flusso-piroclastico-scorre-sul-mare-esempi-a-stromboli-e-altri-vulcani/|access-date=2021-10-04|website=INGV vulcani|language=it-IT}}</ref>

A pyroclastic flow can interact with a body of water to form a large amount of mud, which can then continue to flow downhill as a [[lahar]]. This is one of several mechanisms that can create a lahar.{{citation needed|date=July 2020}}