View source for Tephra

{{short description|Fragmental material produced by a volcanic eruption}}
{{Redirect|Pyroclasts|the Sunn O))) album|Pyroclasts (album)|5=Pyroclastic (disambiguation)}}
{{Redirect|Tefra|the Tax Equity and Fiscal Responsibility Act of 1982|TEFRA}}
{{See also|Volcanic ash}}
{{Use dmy dates|date=May 2020}}
[[File:Brown Bluff-2016-Tabarin Peninsula–Volcanic tephra.jpg|thumb|Volcanic tephra at [[Brown Bluff]], Antarctica (2016)]]

'''Tephra''' is fragmental material produced by a [[Volcano|volcanic eruption]] regardless of composition, fragment size, or emplacement mechanism.<ref>This is the broad definition of tephra (Greek ''tephra'', "ash") proposed by the Icelandic volcanologist [[Sigurður Þórarinsson]] (Sigurdur Thorarinsson) in 1954, in connection with the eruption of [[Hekla]] (Thorarinsson, "The eruption of Hekla, 1947-48II, 3, The tephra-fall from Hekla, March 29th, 1947", ''Visindafélag Íslendinga'' (1954:1-3). The term had been used earlier in Sigurdur Thorarinsson's 1944 doctoral studies, but not in English. See {{cite journal|last1 =Thorarinsson| first1 =S|year =1944|title =Tefrokronologiska studier pA Island|journal =Geografiska Annaler|volume =26|issue =1–2|pages =1–217|doi =10.1080/20014422.1944.11880727|author-link =Sigurður Þórarinsson}}</ref>

[[Image:Icelandic tephra.JPG|thumb|Tephra horizons in south-central [[Iceland]]: The thick and light-coloured layer at the centre of the photo is [[rhyolitic]] tephra from [[Hekla]].]]
[[Volcanologist]]s also refer to airborne fragments as '''pyroclasts'''. Once clasts have fallen to the ground, they remain as tephra unless hot enough to fuse into [[pyroclastic rock]] or [[tuff]]. When a volcano explodes, it releases a variety of tephra including ash, cinders, and blocks. These layers settle on the land and, over time, [[sedimentation]] occurs incorporating these tephra layers into the geologic record.

[[Tephrochronology]] is a geochronological technique that uses discrete layers of tephra—volcanic ash from a single eruption—to create a chronological framework in which [[Paleoecology|paleoenvironmental]] or [[Archaeology|archaeological]] records can be placed. Often, when a volcano explodes, biological organisms are killed and their remains are buried within the tephra layer. These fossils are later dated by scientists to determine the age of the [[fossil]] and its place within the geologic record.
[[File:Lava fountain at Kilauea.jpg|thumb|Molten [[lava fountain]] at [[Kilauea]] volcano on Hawaii, with black cloud of associated tephra]]

==Overview==
[[File:BishopTuff.jpg|thumb|Rocks from the [[Bishop tuff]], uncompressed with [[pumice]] on left; compressed with [[fiamme]] on right]]
Tephra is any sized or composition pyroclastic material produced by an explosive volcanic eruption and precise geological definitions exist.<ref name=Lowe>{{cite journal|title=Global tephra studies: role and importance of the international tephra research group 'Commission on Tephrochronology' in its first 60 years|first1=David J. |last1=Lowe |first2= Peter M. |last2=Abbott |first3= Takehiko |last3=Suzuki |first4= Britta J. L. |last4=Jensen |journal= History of Geo-Space Sciences|volume=13 |pages=93–132 |year= 2022 |issue=2 |doi=10.5194/hgss-13-93-2022 |bibcode=2022HGSS...13...93L |url=https://www.researchgate.net/publication/360927283 |doi-access=free |hdl=10289/15024 |hdl-access=free }}</ref> It consists of a variety of materials, typically glassy particles formed by the cooling of droplets of [[magma]], which may be vesicular, solid or flake-like, and varying proportions of crystalline and mineral components originating from the mountain and the walls of the vent. As the particles fall to the ground, they are sorted to a certain extent by the wind and gravitational forces and form layers of unconsolidated material. The particles are further moved by ground surface or submarine water flow.<ref name=Gornitz>{{cite book|author=Gornitz, Vivien |title=Encyclopedia of Paleoclimatology and Ancient Environments|url=https://books.google.com/books?id=yRMgYc-8mTIC&pg=PA937 |year=2008 |publisher=Springer Science & Business Media|isbn=978-1-4020-4551-6 |pages=937–938}}</ref>

The distribution of tephra following an eruption usually involves the largest boulders falling to the ground quickest, therefore closest to the vent, while smaller fragments travel further&nbsp;– ash can often travel for thousands of miles, even circumglobal, as it can stay in the [[stratosphere]] for days to weeks following an eruption.
When large amounts of tephra accumulate in the atmosphere from massive volcanic eruptions (or from a multitude of smaller eruptions occurring simultaneously), they can reflect light and heat from the sun back through the atmosphere, in some cases causing the temperature to drop, resulting in a temporary "[[volcanic winter]]". The effects of acidic rain and snow, the precipitation caused by tephra discharges into the atmosphere, can be seen for years after the eruptions have stopped. Tephra eruptions can affect ecosystems across millions of square kilometres or even entire continents depending on the size of the eruption.<ref name="Ayris 1905–1936">{{Cite journal|last1=Ayris|first1=Paul Martin|last2=Delmelle|first2=Pierre|date=1 November 2012|title=The immediate environmental effects of tephra emission|journal=Bulletin of Volcanology|language=en|volume=74|issue=9|pages=1905–1936|doi=10.1007/s00445-012-0654-5|bibcode=2012BVol...74.1905A|s2cid=129369735|issn=1432-0819}}</ref>

==Classification==
[[Image:Volcanic breccia in Jackson Hole.JPG|thumb|Volcanic [[breccia]] in [[Jackson Hole]]]]

Tephra fragments are classified by size:
* [[Volcanic ash|Ash]] – particles smaller than 2&nbsp;mm (0.08 inches) in diameter
* [[Lapilli]] or [[Scoria|volcanic cinder]]s – between 2 and 64&nbsp;mm (0.08 and 2.5 inches) in diameter
* [[Volcanic bomb]]s or [[volcanic blocks]] – larger than 64&nbsp;mm (2.5 inches) in diameter

Tephra consisting of very small pyroclastic rock particles in the 25–125 [[μm]] size range, invisible to the naked eye, is also called '''cryptotephra'''.<ref name="Pyle_2016">{{cite book |chapter=Chapter 1 - Field Observations of Tephra Fallout Deposits |title=Volcanic Ash: Hazard Observation |publisher=Elsevier |last=Pyle |first=D.M. |editor1-last=Mackie |editor1-first=S. |editor2-last=Cashman |editor2-first=K. |editor3-last=Ricketts |editor3-first=H. |editor4-last=Rust |editor4-first=A. |editor5-last=Watson |editor5-first=M. |year=2016 |pages=25–37 |doi=10.1016/B978-0-08-100405-0.00004-5 |isbn=978-0-08-100405-0}}</ref>

The use of tephra layers, which bear their own unique chemistry and character, as temporal [[marker horizon]]s in archaeological and geological sites, is known as [[tephrochronology]].<ref name=Gornitz/>

==Etymology==
The word "tephra" and "pyroclast" both derive from [[Ancient Greek|Greek]]: The word {{lang|grc|[[wikt:τέφρα#Ancient Greek|τέφρα]]}} ({{Transliteration|grc|téphra}}) means "ash",<ref>{{LSJ|te/fra|τέφρα|ref}}.</ref> while ''pyroclast'' is derived from the Greek {{lang|grc|[[wikt:πῦρ|πῦρ]]}} ({{Transliteration|grc|pyr}}), meaning "fire",<ref>{{LSJ|pu{{=}}r|πῦρ|shortref}}.</ref> and {{lang|grc|[[wikt:κλαστός|κλαστός]]}} ({{Transliteration|grc|klastós}}), meaning "broken in pieces".<ref>{{LSJ|klasto/s|κλαστός|shortref}}.</ref> The word {{lang|grc|[[wikt:τέφραv#Ancient Greek|τέφραv]]}} (means "ashes") is used in broad context within an account by Aristotle of an eruption on [[Vulcano]] (Hiera) in ''Meteorologica''.<ref>{{cite web|url=https://www.loebclassics.com/view/aristotle-meteorlogica/1952/pb_LCL397.211.xml|publisher =Harvard University Press|title= Greek-English translation Aristotle, Meteorologica LCL 397: 210-211 paragraph 367 |doi =10.4159/DLCL.aristotle-meteorlogica.1952 |author-link =Aristotle|last1=Ἀριστοτέλης|date =1952|s2cid =245028937|access-date =13 December 2023}}</ref>

== Environmental effects ==
The release of tephra into the [[troposphere]] affects the [[Natural environment|environment]] physically and chemically. Physically, volcanic blocks damage local flora and human settlements. Ash damages communication and electrical systems, coats forests and plant life, reducing [[photosynthesis]], and pollutes [[groundwater]].<ref>{{Cite web|title=USGS: Volcano Hazards Program|url=https://volcanoes.usgs.gov/vhp/tephra.html|website=volcanoes.usgs.gov|access-date=19 March 2020}}</ref> Tephra changes below- and above-ground air and water movement. Chemically, tephra release can affect the [[water cycle]]. Tephra particles can cause [[ice crystals]] to grow in clouds, which increases [[precipitation]]. Nearby watersheds and the [[ocean]] can experience elevated [[mineral]] levels, especially [[iron]], which can cause explosive population growth in [[plankton]] communities.<ref name="Ayris 1905–1936"/> This, in turn, can result in [[eutrophication]].

== Disciplines and fossil record ==
In addition to tephrochronology, tephra is used by a variety of scientific disciplines including [[geology]], [[paleoecology]], [[anthropology]], and [[paleontology]], to date fossils, identify dates within the fossils record, and learn about prehistoric cultures and ecosystems. For example, [[carbonatite]] tephra found at [[Oldoinyo Lengai]] (a volcano in the East African Rift Valley) has buried and preserved fossilized footprints of humans near the site of the eruption.<ref name="Hay1989">{{cite journal | title=Holocene carbonatite-nephelinite tephra deposits of Oldoinyo Lengai, Tanzania | first=R. L. | last=Hay | journal=Journal of Volcanology and Geothermal Research | year=1989 | volume=37 | issue=1 | pages=77–91 | doi=10.1016/0377-0273(89)90114-5| bibcode=1989JVGR...37...77H }}</ref> Under certain conditions, volcanic blocks can be preserved for billions of years{{citation needed|date=September 2021}} and can travel up to 400&nbsp;km away from the eruption.{{citation needed|date=September 2021}} Volcanic eruptions around the world have provided valuable scientific information on local ecosystems and ancient cultures.{{citation needed|date=September 2021}}

==Volcanoes==

=== Africa ===
The [[Waw an Namus]] volcano is surrounded by an apron of dark tephra, which has a notable color contrast to the surrounding [[Sahara Desert]].

Africa's volcanoes have had an impact on the fossil record. Geographically a part of Africa, [[El Hierro]] is a shield volcano and the youngest and smallest of the [[Canary Islands]]. The most recent [[El Hierro eruption]] occurred underwater, in 2011, and caused earthquakes and landslides throughout the Canary Islands. Instead of ash, floating rocks, 'restingolites' were released after every eruption.<ref>{{Cite web|title=Global Volcanism Program {{!}} Hierro|url=https://volcano.si.edu/volcano.cfm?vn=383020|website=Smithsonian Institution {{!}} Global Volcanism Program|language=en|access-date=19 March 2020}}</ref> After the 2011 eruption, fossils of single-celled marine organisms were found in the restingolites verifying the origin theory that Canary Island growth comes from a single buoyant jet of magma from the Earth's core instead of cracks in the ocean floor. This is reflected in the decreasing age of the islands east to west from [[Fuerteventura]] to El Hierro.<ref>{{Cite web|title=Fossils survive volcanic eruption to tell us about the origin of the Canary Islands|url=https://www.sciencedaily.com/releases/2015/01/150122084539.htm|website=ScienceDaily|language=en|access-date=19 March 2020}}</ref>

There are about 60 volcanoes in Ethiopia, located in east Africa. In Southern Ethiopia, the Omo Kibish Rock Formation is composed of layers of tephra and sediment. Within these layers, several fossils have been discovered. In 1967, 2 ''Homo sapiens'' fossils were discovered in the [[Omo Kibish Formation]] by [[Richard Leakey|Richard Leaky]], a paleoanthropologist. After radiocarbon dating, they were determined to be 195 thousand years old.<ref>{{Cite journal|last1=Brown|first1=Francis H.|last2=Fuller|first2=Chad R.|date=September 2008|title=Stratigraphy and tephra of the Kibish Formation, southwestern Ethiopia|journal=Journal of Human Evolution|language=en|volume=55|issue=3|pages=366–403|doi=10.1016/j.jhevol.2008.05.009|pmid=18692219|bibcode=2008JHumE..55..366B }}</ref> Other mammals discovered in the formation include ''[[Giant forest hog|Hylochoerus]] meinertzhageni'' (forest hog) and ''[[Cephalophus]]'' (antelope).<ref>{{Cite journal |last1=Assefa |first1=Zelalem |last2=Yirga |first2=Solomon |last3=Reed |first3=Kaye E. |author-link3=Kaye Reed |date=September 2008 |title=The large-mammal fauna from the Kibish Formation |url=http://doc.rero.ch/record/210304/files/PAL_E4355.pdf |journal=Journal of Human Evolution |language=en |volume=55 |issue=3 |pages=501–512 |doi=10.1016/j.jhevol.2008.05.015 |pmid=18691734 |bibcode=2008JHumE..55..501A |s2cid=5923387}}</ref>

=== Asia ===
[[File:Sakurajima eruptions 8 Dec. 2014, JST 13-45-44 (cropped).JPG|thumb|Tephra and volcanic gas erupting explosively from [[Sakurajima]], Japan, in 2014, with some of the tephra falling back onto the ground]]
In Asia, several volcanic eruptions are still influencing local cultures today. In North Korea, [[Paektu Mountain]], a stratovolcano, first erupted in 946 AD and is a religious site for locals. It last erupted in 1903. In 2017, new fossil evidence was discovered that determined the date of Paektu Mountain's first eruption, which had been a mystery. A team of scientists directed by Dr. Clive Oppenheimer, British [[volcanologist]], discovered a larch trunk embedded within Paektu Mountain. After radiocarbon dating, the larch was determined to be 264 years old which coincides with the 946 AD eruption. Its tree rings are being studied and many new discoveries are being made about [[North Korea]] during that time.<ref>{{Cite web|title=Fossilized tree and ice cores help date huge volcanic eruption 1,000 years ago to within three months|url=https://www.sciencedaily.com/releases/2017/01/170129111657.htm|website=ScienceDaily|language=en|access-date=19 March 2020}}</ref>

In northeastern China, a large volcanic eruption in the early [[Cretaceous]] caused the fossilization of an entire ecosystem known as the [[Jehol Biota]] when powerful [[pyroclastic flow]]s inundated the area. The deposits include many perfectly preserved fossils of [[dinosaur]]s, [[bird]]s, [[mammal]]s, [[reptile]]s, [[fish]], [[frog]]s, [[plant]]s, and [[insect]]s.<ref>{{Cite web|title=Pompeii-style volcano gave China its dinosaur trove|url=https://phys.org/news/2014-02-pompeii-style-volcano-gave-china-dinosaur.html|website=phys.org|language=en-us|access-date=19 March 2020}}</ref>

=== Europe ===
Europe's volcanoes provide unique information about the history of [[Italy]]. One example is [[Mount Vesuvius]], a stratovolcano located in southern Italy,<ref>{{Cite web|title=Everything about the volcanoes in Italy|url=https://www.zmescience.com/science/geology/italy-volcanoes-etna-vesuvius/|date=24 September 2015|website=ZME Science|language=en-US|access-date=19 March 2020}}</ref> which last erupted in March 1944. Earlier, in 79 AD, in an eruption which lasted 12 to 18 hours, Vesuvius had covered the city of [[Pompeii]] in molten lava, ash, pumice, volcanic blocks, and toxic gases. Much of the town was preserved and organic materials fossilized by the volcanic ash, and that has provided valuable information about the [[Ancient Rome|Roman]] culture.<ref>{{Cite web|title=Mount Vesuvius erupts|url=https://www.history.com/this-day-in-history/vesuvius-erupts|website=HISTORY|date=24 November 2009 |language=en|access-date=19 March 2020}}</ref> Also, in Italy, [[Stromboli (volcano)|Stromboli volcano]], a stratovolcano, last erupted in July 2019.

=== North America ===
[[File:606_Mt_St_Helens_NVM,_ash_covered_landscape_(35404396313).jpg|thumb|The [[Mount St. Helens]] National Volcanic Monument after the 1980 eruption]]
Several volcanic eruptions have been studied in [[North America]]. On 18 May 1980, [[Mount St. Helens]], a stratovolcano in [[Washington (state)|Washington state]], erupted, spreading five hundred million tons of tephra ash across Washington, Oregon, [[Montana]] and [[Idaho]] causing [[earthquake]]s, [[rockslide]]s, and [[megatsunami]] which severely altered the topography of nearby areas.<ref>{{Cite web|title=Cascades Volcano Observatory|url=https://volcanoes.usgs.gov/observatories/cvo/cascade_tephra.html|website=volcanoes.usgs.gov|access-date=19 March 2020|archive-date=29 May 2020|archive-url=https://web.archive.org/web/20200529235224/https://volcanoes.usgs.gov/observatories/cvo/cascade_tephra.html|url-status=dead}}</ref> In [[Yellowstone National Park]], eruption-related flooding caused trees to collapse and wash into lake beds where they fossilized. Nearby forests were flooded, removing bark, leaves, and tree limbs.<ref>{{Cite web|title=Petrified Trees {{!}} Fossilized Trees {{!}} Mount St. Helens Eruption|url=https://amazingdiscoveries.org/C-deception-fossils_petrified_trees_catastrophism|last=Discoveries|first=Amazing|website=amazingdiscoveries.org|language=en|access-date=19 March 2020}}</ref> In 2006, the Augustine Volcano in Alaska erupted generating earthquakes, [[avalanche]]s, and projected tephra ash approximately two hundred and ninety kilometers away. This dome volcano is over forty thousand years old and has erupted 11 times since 1800.<ref>{{Cite web|title=Augustine {{!}} Volcano World {{!}} Oregon State University|url=http://volcano.oregonstate.edu/augustine|website=volcano.oregonstate.edu|date=4 May 2010 |access-date=19 March 2020}}</ref>

=== South America ===
[[File:Chaitén Volcano Lava Dome, Chile.jpg|thumb|Satellite image of Chaitén volcano lava dome, Chile: The circular dome is brown and is surrounded by an ash covered landscape.]]
In [[South America]], there are several historic active volcanoes. In southern [[Chile]], the [[Chaitén (volcano)|Chaitén volcano]] erupted in 2011 adding 160 meters to its rim. Prehistoric weapons and tools, formed from [[obsidian]] tephra blocks, were dated at 5,610 years ago and were discovered 400&nbsp;km away.<ref>{{Cite web|title=Chaitén Volcano, Chile: Map, Facts, Eruption Pictures {{!}} Chaiten|url=https://geology.com/volcanoes/chaiten/|website=geology.com|access-date=19 March 2020}}</ref> Due to the location of the [[Subduction|subduction zone]] of the eastern Pacific's Nazca Plate, there are twenty one active volcanoes in southern [[Peru]].<ref>{{Cite web|title=Volcanoes of Peru|url=https://www.volcanodiscovery.com/peru.html|website=www.volcanodiscovery.com|access-date=19 March 2020}}</ref> In 2006, fossils, found under a layer of volcanic ash in Peru, were excavated by a team of paleontologists led by Mark D. Uhen, professor at George Mason University. The fossils were identified as 3 different types of archaeocetes, prehistoric whales, and are older than 36.61&nbsp;million years which, {{As of|2011|lc=y}}, makes them South America's oldest whale fossils.<ref>{{Cite web|title=New Archaeocetes from Peru Are the Oldest Fossil Whales from South America {{!}} Smithsonian Ocean|url=http://ocean.si.edu/ocean-life/marine-mammals/new-archaeocetes-peru-are-oldest-fossil-whales-south-america|last=Pyenson|first=Nicholas D.|author1-link=Nicholas Pyenson|website=ocean.si.edu|language=en|access-date=19 March 2020}}</ref>

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==References==
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== External links ==
* {{Commons category-inline}}
* [https://web.archive.org/web/20051216120850/http://facweb.bhc.edu/academics/science/harwoodr/GEOL101/Labs/VolcanicMaterials/ Volcanic materials identification]

{{Volcanoes}}

[[Category:Tephra| ]]
[[Category:Igneous petrology]]

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