Lapilli: Difference between revisions
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{{Short description|Small pyroclast debris thrown in the air by a volcanic eruption}} |
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[[File:PuuPuaiLapilli large.jpg|thumb|right|340px|Lapilli on [[Kilauea]] |
[[File:PuuPuaiLapilli large.jpg|thumb|right|340px|Lapilli on [[Kilauea]]]] |
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'''Lapilli''' is a size classification |
'''Lapilli''' ({{singular}}: '''lapillus''') is a size classification of [[tephra]], which is material that falls out of the air during a [[volcano|volcanic eruption]] or during some [[meteorite impact]]s.<ref name="Bron">{{cite book|last=Bron|first=K.A.|editor=Reimold W.U. & Gibson R.L.|title=Large Meteorite Impacts and Planetary Evolution IV|chapter-url=https://books.google.com/books?id=YB6Xw6rYwksC&q=accretionary+lapilli+meteorite+impact+events&pg=PA222|access-date=22 May 2011|series=Special Paper|volume=465|year=2010|publisher=The Geological Society of America|isbn=978-0-8137-2465-2|page=222|chapter=Accretionary and melt impactoclasts from the Tookoonooka impact event, Australia}}</ref> ''Lapilli'' is Latin for "little stones". |
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By definition lapilli range from {{convert|2|to|64|mm|in|2|abbr=on}} in diameter.<ref>Fisher |
By definition lapilli range from {{convert|2|to|64|mm|in|2|abbr=on}} in diameter.<ref>{{cite journal|last1=Fisher|first1= R. V.|date=1961|title= Proposed classification of volcaniclastic sediments and rocks|doi=10.1130/0016-7606(1961)72[1409:PCOVSA]2.0.CO;2|journal=Geological Society of America Bulletin|volume= 72|issue=9|pages= 1409–1414|bibcode=1961GSAB...72.1409F}}</ref> A [[Pyroclastic rock|pyroclastic]] particle greater than 64 mm in diameter is known as a [[volcanic bomb]] when molten, or a volcanic block when solid. Pyroclastic material with particles less than 2 mm in diameter is referred to as [[volcanic ash]].<ref>[http://volcanoes.usgs.gov/images/pglossary/lapilli.php VHP Photo Glossary: Laplli] in USGS Photo Glossary of volcano terms]</ref><ref>[http://www.geology.sdsu.edu/how_volcanoes_work/Tephra.html How Volcanoes Work]</ref> |
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==Formation== |
==Formation== |
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[[File:Lapilli 850.jpg|thumb|340px|Lapilli on [[Fuerteventura]].]] |
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| ⚫ | Lapilli are spheroid, teardrop, dumbbell or button-shaped droplets of molten or semi-molten [[lava]] ejected from a volcanic eruption that fall to earth while still at least partially molten. |
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Lapilli [[tuff]]s are a very common form of volcanic rock typical of [[rhyolite]], [[andesite]] and [[dacite]] pyroclastic eruptions |
Lapilli [[tuff]]s are a very common form of volcanic rock typical of [[rhyolite]], [[andesite]] and [[dacite]] pyroclastic eruptions, where thick layers of lapilli can be deposited during a basal surge eruption. Most lapilli tuffs which remain in ancient terrains are formed by the accumulation and ''welding'' of semi-molten lapilli into what is known as a [[Tuff#Welded tuff|welded tuff]]. |
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The heat of the newly deposited volcanic pile tends to cause the semi-molten material to flatten out |
The heat of the newly deposited volcanic pile tends to cause the semi-molten material to flatten out and then become welded. Welded tuff [[rock microstructure|textures]] are distinctive (termed ''[[eutaxitic]]''), with flattened lapilli, [[fiamme]], blocks and bombs forming oblate to discus-shaped forms within layers. These rocks are quite indurated and tough, as opposed to non-welded lapilli tuffs, which are unconsolidated and easily [[eroded]]. |
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===Accretionary |
===Accretionary lapilli=== |
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| ⚫ | Rounded balls of [[tephra]] are called ''accretionary lapilli'' if they consist of layered [[volcanic ash]] particles. Accretionary lapilli are formed by a process of wet [[Volcanic ash aggregation|ash aggregation]] due to moisture in volcanic clouds that sticks the particles together, with the volcanic ash nucleating on some object and then accreting to it in layers before the accretionary lapillus falls from the cloud. Accretionary lapilli are like volcanic hailstones that form by the addition of concentric layers of moist ash around a central nucleus. |
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| ⚫ | Rounded [[tephra]] |
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These lapilli are a variety of accretionary lapilli, though they contain lithic or crystal cores coated by rinds of coarse to fine ash. Armoured lapilli only form in hydroclastic eruptions, where significant moisture is present. The vapour column contains cohesive ash which sticks to particles within it. |
These lapilli are a variety of accretionary lapilli, though they contain lithic or crystal cores coated by rinds of coarse to fine ash. Armoured lapilli only form in hydroclastic eruptions, where significant moisture is present. The vapour column contains cohesive ash which sticks to particles within it. |
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== See also == |
== See also == |
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*[[Tuff]] |
* [[Tuff]] |
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*[[ |
* [[Scoria]] |
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* [[Rock microstructure]] |
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*[[Cinder]] |
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*[[Lava]] |
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*[[Rock microstructure|Rock microstructure of volcanic rocks]] |
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==References== |
==References== |
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<references/> |
<references /> |
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== External links == |
== External links == |
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{{Wiktionary|lapilli}} |
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*[http://volcanoes.usgs.gov/Products/Pglossary/AccretLap.html USGS Photo glossary of volcano terms] |
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*[http://www.geology.sdsu.edu/how_volcanoes_work/Tephra.html How Volcanoes Work] |
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* {{cite web|author=Zentner, Nick|title=Supervolcanoes in the Pacific Northwest|date=25 April 2019|website=YouTube|url=https://www.youtube.com/watch?v=NcreTTI9Rew&t=2704 |archive-url=https://ghostarchive.org/varchive/youtube/20211212/NcreTTI9Rew| archive-date=2021-12-12 |url-status=live}}{{cbignore}} (segment on accretionary lapilli beginning at 45:04 in video) |
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{{Volcanoes}} |
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[[Category:Tephra]] |
[[Category:Tephra]] |
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Latest revision as of 15:44, 5 July 2024
Lapilli (sg.: lapillus) is a size classification of tephra, which is material that falls out of the air during a volcanic eruption or during some meteorite impacts.[1] Lapilli is Latin for "little stones".
By definition lapilli range from 2 to 64 mm (0.08 to 2.52 in) in diameter.[2] A pyroclastic particle greater than 64 mm in diameter is known as a volcanic bomb when molten, or a volcanic block when solid. Pyroclastic material with particles less than 2 mm in diameter is referred to as volcanic ash.[3][4]
Formation
[edit]Lapilli are spheroid-, teardrop-, dumbbell- or button-shaped droplets of molten or semi-molten lava ejected from a volcanic eruption that fall to earth while still at least partially molten. These granules are the direct result of liquid rock cooling as it travels through the air.
Lapilli tuffs are a very common form of volcanic rock typical of rhyolite, andesite and dacite pyroclastic eruptions, where thick layers of lapilli can be deposited during a basal surge eruption. Most lapilli tuffs which remain in ancient terrains are formed by the accumulation and welding of semi-molten lapilli into what is known as a welded tuff.
The heat of the newly deposited volcanic pile tends to cause the semi-molten material to flatten out and then become welded. Welded tuff textures are distinctive (termed eutaxitic), with flattened lapilli, fiamme, blocks and bombs forming oblate to discus-shaped forms within layers. These rocks are quite indurated and tough, as opposed to non-welded lapilli tuffs, which are unconsolidated and easily eroded.
Accretionary lapilli
[edit]
Rounded balls of tephra are called accretionary lapilli if they consist of layered volcanic ash particles. Accretionary lapilli are formed by a process of wet ash aggregation due to moisture in volcanic clouds that sticks the particles together, with the volcanic ash nucleating on some object and then accreting to it in layers before the accretionary lapillus falls from the cloud. Accretionary lapilli are like volcanic hailstones that form by the addition of concentric layers of moist ash around a central nucleus.
This texture can be confused with spherulitic and axiolitic texture.
Armoured (or cored) lapilli
[edit]These lapilli are a variety of accretionary lapilli, though they contain lithic or crystal cores coated by rinds of coarse to fine ash. Armoured lapilli only form in hydroclastic eruptions, where significant moisture is present. The vapour column contains cohesive ash which sticks to particles within it.
See also
[edit]References
[edit]- ^ Bron, K.A. (2010). "Accretionary and melt impactoclasts from the Tookoonooka impact event, Australia". In Reimold W.U. & Gibson R.L. (ed.). Large Meteorite Impacts and Planetary Evolution IV. Special Paper. Vol. 465. The Geological Society of America. p. 222. ISBN 978-0-8137-2465-2. Retrieved 22 May 2011.
- ^ Fisher, R. V. (1961). "Proposed classification of volcaniclastic sediments and rocks". Geological Society of America Bulletin. 72 (9): 1409–1414. Bibcode:1961GSAB...72.1409F. doi:10.1130/0016-7606(1961)72[1409:PCOVSA]2.0.CO;2.
- ^ VHP Photo Glossary: Laplli in USGS Photo Glossary of volcano terms]
- ^ How Volcanoes Work
External links
[edit]
- Volcanic Materials Identification
- Tephra fall from Mt St. Helens
- Zentner, Nick (25 April 2019). "Supervolcanoes in the Pacific Northwest". YouTube. Archived from the original on 2021-12-12. (segment on accretionary lapilli beginning at 45:04 in video)
