Editing Tuff (section)

===High-silica volcanism===
Rhyolite tuffs contain pumiceous, glassy fragments and small scoriae with [[quartz]], [[alkali]] [[feldspar]], [[biotite]], etc. Iceland,<ref>{{cite journal |last1=Jónasson |first1=K. |title=Rhyolite volcanism in the Krafla central volcano, north-east Iceland |journal=Bulletin of Volcanology |date=December 1994 |volume=56 |issue=6–7 |pages=516–528 |doi=10.1007/BF00302832|bibcode=1994BVol...56..516J |s2cid=129012636 }}</ref> Lipari,<ref>{{cite journal |last1=Crisci |first1=G. M. |last2=Rosa |first2=R. |last3=Lanzafame |first3=G. |last4=Mazzuoli |first4=R. |last5=Sheridan |first5=M. F. |last6=Zuffa |first6=G. G. |display-authors=3|title=Monte guardia sequence: a late-pleistocene eruptive cycle on Lipari (Italy) |journal=Bulletin Volcanologique |date=September 1981 |volume=44 |issue=3 |pages=241–255 |doi=10.1007/BF02600562|bibcode=1981BVol...44..241C |s2cid=128627430 }}</ref> Hungary,<ref>{{cite journal |last1=Zelenka |first1=Tibor |last2=Balázs |first2=Endre |last3=Balogh |first3=Kadosa |last4=Kiss |first4=János |title=Buried Neogene volcanic structures in Hungary |journal=Acta Geologica Hungarica |date=December 2004 |volume=47 |issue=2–3 |pages=177–219 |doi=10.1556/ageol.47.2004.2-3.6|url=http://real.mtak.hu/33118/1/zelenka_eltemtett_vulk_2004.pdf }}</ref> the [[Basin and Range Province|Basin and Range]] of the American southwest, and [[New Zealand]]{{sfn|Philpotts|Ague|2009|p=77}} are among the areas where such tuffs are prominent. In the ancient rocks of [[Wales]],<ref>{{cite journal |last1=Howells |first1=M. F. |last2=Reedman |first2=A. J. |last3=Campbell |first3=S. D. G. |title=The submarine eruption and emplacement of the Lower Rhyolitic Tuff Formation (Ordovician), N Wales |journal=Journal of the Geological Society |date=May 1986 |volume=143 |issue=3 |pages=411–423 |doi=10.1144/gsjgs.143.3.0411|bibcode=1986JGSoc.143..411H |s2cid=129147300 }}</ref> [[Charnwood Forest|Charnwood]],<ref>{{cite journal |last1=Carney |first1=John |title=Igneous processes within late Precambrian volcanic centres near Whitwick, northwestern Charnwood Forest |journal=Mercian Geologist |date=2000 |volume=15 |issue=1 |pages=7–28 |url=http://www.emgs.org.uk/files/mercian_vol13on/Mercian%20Geologist%20volume%2015%202000-2003/Mercian%202000%20v15%20p007%20Precambrian%20igneous%20processes%20Charwood,%20Carney.pdf |access-date=1 October 2020 |archive-date=28 September 2022 |archive-url=https://web.archive.org/web/20220928065307/http://www.emgs.org.uk/files/mercian_vol13on/Mercian%20Geologist%20volume%2015%202000-2003/Mercian%202000%20v15%20p007%20Precambrian%20igneous%20processes%20Charwood,%20Carney.pdf |url-status=dead }}</ref> etc., similar tuffs are known, but in all cases, they are greatly changed by silicification (which has filled them with [[opal]], [[chalcedony]], and quartz) and by devitrification.<ref>{{cite journal |last1=McArthur |first1=A. N. |last2=Cas |first2=R. A. F. |last3=Orton |first3=G. J. |title=Distribution and significance of crystalline, perlitic and vesicular textures in the Ordovician Garth Tuff (Wales) |journal=Bulletin of Volcanology |date=30 November 1998 |volume=60 |issue=4 |pages=260–285 |doi=10.1007/s004450050232|bibcode=1998BVol...60..260M |s2cid=128474768 }}</ref> The frequent presence of rounded corroded quartz crystals, such as occur in rhyolitic lavas, helps to demonstrate their real nature.<ref name=EB1911/>

Welded ignimbrites can be highly voluminous, such as the [[Lava Creek Tuff]] erupted from [[Yellowstone Caldera]] in [[Wyoming]] 631,000 years ago. This tuff had an original volume of at least {{convert|1000|km3|cumi|sp=us}}.<ref>{{cite journal |last1=Matthews |first1=Naomi E. |last2=Vazquez |first2=Jorge A. |last3=Calvert |first3=Andrew T. |title=Age of the Lava Creek supereruption and magma chamber assembly at Yellowstone based on 40 Ar/ 39 Ar and U-Pb dating of sanidine and zircon crystals: AGE OF THE LAVA CREEK SUPERERUPTION |journal=Geochemistry, Geophysics, Geosystems |date=August 2015 |volume=16 |issue=8 |pages=2508–2528 |doi=10.1002/2015GC005881|s2cid=131340369 }}</ref> Lava Creek tuff is known to be at least 1000 times as large as the deposits of the [[1980 eruption of Mount St. Helens]], and it had a [[Volcanic Explosivity Index]] (VEI) of 8, greater than any eruption known in the last 10,000 years.<ref>{{cite web |title=What is a supervolcano? What is a supereruption? |url=https://www.usgs.gov/faqs/what-a-supervolcano-what-a-supereruption?qt-news_science_products=0#qt-news_science_products |website=Natural Hazards |publisher=United States Geological Survey |access-date=30 September 2020}}</ref> Ash flow tuffs cover {{convert|7000|km2|sqmi|sp=us}} of the [[North Island]] of [[New Zealand]] and about {{convert|100000|km2|sqmi|sp=us}} of [[Nevada]]. Ash flow tuffs are the only volcanic product with volumes rivaling those of [[flood basalt]]s.{{sfn|Philpotts|Ague|2009|p=77}}

The Tioga Bentonite of the northeastern United States varies in composition from crystal tuff to tuffaceous shale. It was deposited as ash carried by wind that fell out over the sea and settled to the bottom. It is [[Devonian]] in age and likely came from a vent in central [[Virginia]], where the tuff reaches its maximum thickness of about {{convert|40|meters|feet|sp=us}}.<ref>{{cite journal |last1=Dennison |first1=J. M. |last2=Textoris |first2=D. A. |title=Devonian tioga tuff in Northeastern United States |journal=Bulletin Volcanologique |date=March 1970 |volume=34 |issue=1 |pages=289–294 |doi=10.1007/BF02597791|bibcode=1970BVol...34..289D |s2cid=129708915 }}</ref>