Editing Ejecta

{{short description|Particles ejected from an area}}
{{other uses}}
[[File:MSH80 st helens eruption plume 07-22-80.jpg|thumb|Mt. St Helens eruption plume on 22 July 1980, showing ejecta in the form of pyroclastic material (ash)]]

'''Ejecta''' ({{langnf|la||things thrown out}}; {{singular abbr|'''ejectum'''}}) are [[particle]]s ejected from an area. In [[volcanology]], in particular, the term refers to particles including [[pyroclastic rock|pyroclastic]] materials ([[tephra]]) that came out of a [[explosive eruption|volcanic explosion]] and magma eruption [[volcano|volcanic]] vent, or [[volcanic crater|crater]], has traveled through the air or water, and fell back to the ground surface or [[seabed|ocean floor]].

== Volcanology  ==
Typically in [[volcanology]], ejecta is a result of [[explosive eruption]]s. In an explosive eruption, large amounts of [[volcanic gas|gas]] are dissolved in extremely [[viscous]] lava; this lava froths to the surface until the material is expelled rapidly due to the trapped pressure. Sometimes in such an event a lava plug or [[volcanic neck]] forms from lava that solidifies inside a volcano's vent, causing heat and pressure to build up to an extreme with no way to escape. When the blockage breaks and cannot sustain itself any longer, a more violent eruption occurs, which allows materials to be ejected out of the volcano.<ref>[http://www.landforms.eu/Lothian/volcanic%20neck.htm] {{Webarchive|url=https://web.archive.org/web/20180926124457/http://www.landforms.eu/Lothian/volcanic%20neck.htm|date=2018-09-26}}, Volcanic Neck, Volcanic Plug, USGS.</ref><ref>[http://chis.nrcan.gc.ca/volcano-volcan/hazard-risque-en.php?wbdisable=true], Ejecta, Natural Resources Canada.</ref>

Ejecta can consist of:
# juvenile particles – (fragmented [[magma]] and free [[crystal]]s)
# cognate or accessory particles – older [[volcanic rock]]s from the same [[volcano]]
# accidental particles – derived from the [[Rock (geology)|rocks]] under the volcano

These particles may vary in size; [[tephra]] can range from ash (<{{convert|1//10|in|cm|disp=sqbr}}) or [[lapilli]] (little stones from {{convert|1//10|to|2+1/2|in|cm|disp=or}}) to [[volcanic bomb]]s (>{{convert|2.5|in|cm|disp=sqbr}}).<ref>[http://volcano.oregonstate.edu/glossary/1/letterl#term74] {{Webarchive|url=https://web.archive.org/web/20191129030928/http://volcano.oregonstate.edu/glossary/1/letterl#term74|date=2019-11-29}}, Oregon State University Glossary.</ref>

== Planetary geology ==
{{See also|Panspermia}}
In [[planetary geology]], the term "ejecta" includes debris ejected during the formation of an [[impact crater]].

When an object massive enough hits another object with enough force, it creates a [[shockwave]] that spreads out from the impact. The object breaks and excavates into the ground and rock, at the same time spraying material known as impact ejecta. This ejecta is distributed outward from the crater's rim onto the surface as debris; it can be loose material or a blanket of debris, which thins at the outermost regions.<ref>[https://www.lpi.usra.edu/education/explore/shaping_the_planets/impact-cratering/], Lunar and Planetary Institute.</ref>

Ejecta features are classified based on their distance from the impact crater, the appearance of the ejected material, and the geomorphological characteristics of the terrain. Some common ejecta features include ejecta blankets, radial and concentric ejecta patterns, and secondary craters.<ref>{{Citation |last1=Osinski |first1=Gordon R. |title=Excavation and Impact Ejecta Emplacement |date=2012-11-30 |url=https://onlinelibrary.wiley.com/doi/10.1002/9781118447307.ch4 |work=Impact Cratering |pages=43–59 |editor-last=Osinski |editor-first=Gordon R. |access-date=2023-05-12 |edition=1 |publisher=Wiley |language=en |doi=10.1002/9781118447307.ch4 |isbn=978-1-4051-9829-5 |last2=Grieve |first2=Richard A. F. |last3=Tornabene |first3=Livio L. |editor2-last=Pierazzo |editor2-first=Elisabetta|url-access=subscription }}</ref>

Ejecta Blankets: Ejecta blankets are the continuous layer of debris that surrounds the impact crater, thinning outwards from the crater's rim. The composition of the ejecta blanket can provide valuable information about the geological composition of the impacted surface and the projectile that caused the impact. The distribution and morphology of the ejecta blanket can also provide insight into the impact angle and the dynamics of the ejecta emplacement process.<ref>{{Cite journal |last=Guest |first=J. E. |date=November 1989 |title=H. J. Melosh 1989. Impact Cratering. A Geologic Process. Oxford Monographs on Geology and Geophysics Series no. 11. ix + 245 pp. Oxford: Clarendon Press. Price £45.00 (hard covers). ISBN 0 19 504284 0. |url=https://www.cambridge.org/core/product/identifier/S0016756800007068/type/journal_article |journal=Geological Magazine |language=en |volume=126 |issue=6 |pages=729–730 |doi=10.1017/S0016756800007068 |issn=0016-7568|url-access=subscription }}</ref>

Radial and Concentric Ejecta Patterns: Radial ejecta patterns are characterized by the outward distribution of ejecta from the crater in a series of rays or streaks. These rays are often more prominent in craters formed on solid surfaces, such as the Moon or Mercury. Concentric ejecta patterns are characterized by the presence of multiple, circular layers of ejecta surrounding the impact crater. These patterns are commonly observed on icy surfaces, such as the moons of Jupiter and Saturn, and are indicative of the presence of subsurface volatiles, like water or other ices.<ref>{{Cite journal |last1=Levy |first1=Joseph |last2=Head |first2=James W. |last3=Marchant |first3=David R. |date=October 2010 |title=Concentric crater fill in the northern mid-latitudes of Mars: Formation processes and relationships to similar landforms of glacial origin |url=https://linkinghub.elsevier.com/retrieve/pii/S0019103510001466 |journal=Icarus |language=en |volume=209 |issue=2 |pages=390–404 |doi=10.1016/j.icarus.2010.03.036|bibcode=2010Icar..209..390L |url-access=subscription }}</ref>

If enough ejecta are deposited around an [[impact crater]], it can form an [[ejecta blanket]]; this blanket is full of dust and debris that originated from the initial impact. The size of this impact crater along with the ejecta blanket can be used to determine the size and intensity of the impacting object.  On earth, these ejecta blankets can be analyzed to determine the source location of the impact.<ref>[https://www.nasa.gov/mission_pages/cassini/multimedia/pia07368.html] {{Webarchive|url=https://web.archive.org/web/20170709095809/https://www.nasa.gov/mission_pages/cassini/multimedia/pia07368.html |date=2017-07-09 }}, Titan Impact Crater.</ref>

A lack of impact ejecta around the planet [[Mars]]'s surface feature [[Eden Patera]] was one of the reasons for suspecting in the 2010s that it is a collapsed volcanic [[caldera]] and not an impact crater.<ref>{{Cite news|url=https://www.bbc.com/news/science-environment-24348673|title=Supervolcanoes ripped up early Mars|last=Amos|first=Jonathan|date=2013-10-02|newspaper=BBC News|access-date=2017-02-12|language=en-GB}}</ref>

== Astronomy and heliophysics ==
In [[astrophysics]] or [[heliophysics]], ejecta refers to material expelled in a stellar explosion as in a [[supernova]] or in a [[coronal mass ejection]] (CME).<ref>{{Cite journal|url= http://www.physics.umanitoba.ca/~samar/G21/g21.pdf |title= The Plerionic Supernova Remnant G21.5-0.9: In and Out |journal= Advances in Space Research |volume= 35 |issue= 6 |pages= 1099 |access-date= 2013-09-15 |url-status= dead |archive-url= https://web.archive.org/web/20120717030507/http://www.physics.umanitoba.ca/~samar/G21/g21.pdf |archive-date= 2012-07-17 |doi=10.1016/j.asr.2005.04.050|arxiv=astro-ph/0504369 |year= 2005 |last1= Matheson |first1= Heather |last2= Safi-Harb |first2= Samar |bibcode= 2005AdSpR..35.1099M |citeseerx= 10.1.1.337.6810 |s2cid= 557159 }}</ref><ref>{{cite web |title= The Advanced Satellite for Cosmology and Astrophysics (ASCA) |url= http://heasarc.gsfc.nasa.gov/docs/asca/asca2.html |publisher= Hera.ph1.uni-koeln.de |access-date= 2013-09-15}}</ref><ref>{{cite web|url=http://hera.ph1.uni-koeln.de/~heintzma/X_Ray_Obs/ASCA.htm|title=ASCA|archive-url=https://web.archive.org/web/20060501045323/http://hera.ph1.uni-koeln.de/~heintzma/X_Ray_Obs/ASCA.htm|archive-date=2006-05-01}}</ref>

== Artificial ==
{{Further|Space debris}}

Beside material launched by humans into space with a range of [[launch system]]s, some instances particularly nuclear produce artificial ejecta, like in the case of the [[Operation Plumbbob#Pascal-B|Pascal-B test]] which might have ejected an object with a speed of Earth's [[escape velocity]] into space.<ref name="Brownlee, Harrington">{{cite web
| url =https://www.businessinsider.com/fastest-object-robert-brownlee-2016-2?r=US&IR=T#brownlee-wanted-to-measure-how-fast-the-iron-cap-flew-off-the-column-so-he-designed-a-second-experiment-pascal-b-9 
| author=Harrington, Rebecca   
| date = February 5, 2016
| title = The fastest object ever launched was a manhole cover — here's the story from the guy who shot it into space
| work =[[:wikipedia:Tech Insider|Tech Insider]] - www.businessinsider.com [[:wikipedia:Business Insider|Business Insider]]
|archive-url=
|archive-date=
| accessdate = 11 June 2021}}</ref><ref name="Brownlee, Thomson">{{cite web
| url =https://www.theregister.com/2015/07/16/america_soviets_space_race/ 
| author= Thomson, Iain
| title = SCIENCEDid speeding American manhole cover beat Sputnik into space? Top boffin speaks to El Reg - How a nuke blast lid may have beaten Soviets by months
|date = 16 July 2015
| work =www.theregister.com
|archive-url=
|archive-date=
| accessdate = 11 June 2021}}</ref>

==References==
{{reflist|2}}

[[Category:Volcanology]]
[[Category:Planetary science]]
[[Category:Astrophysics]]