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{{Userspace draft|source=ArticleWizard|date=January 2024}}
{{Short description|Caldera in Alaska}}
{{Infobox mountain
| name = Aniakchak Caldera
| photo = Aniakchak-caldera_alaska.jpg
| photo_caption = Mount Aniakchak caldera
| elevation_ft = 4232
| elevation_ref = <ref name="GNIS">{{cite web
| title = Aniakchak Peak
| work = Geographique Names Information system
| publisher = [[United States Geological Survey]]
| url = http://geonames.usgs.gov/apex/f?p=136:3:0::NO::P3_FID%2CP3_TITLE:1398292%2CAniakchak+Peak
| access-date = 2015-05-05}}</ref>
| prominence =
| map = USA Alaska
| map_relief = 1
| map_caption = Location in Alaska
| map_size = 270
| location = [[Aniakchak National Monument and Preserve]], [[Alaska]], [[United States|USA]]
| coordinates = {{coord|56|51|47|N|158|07|47|W|type:mountain_scale:100000|format=dms|display=inline,title}}
| range = [[Aleutian Range]]<ref name="SI"/>
| coordinates_ref = <ref name="GNIS"/>
| topo = [[United States Geological Survey|USGS]] Chignik D-1
| type = [[Caldera]] ([[Stratovolcano]])<ref name="SI"/><ref name="wood" />
| age =
| volcanic_arc/belt = [[Aleutian Arc]]
| last_eruption = May to June 1931<ref name="GNIS"/>
| first_ascent =
| easiest_route =
| embedded = {{designation list | embed = yes
| designation1 = NNL
| designation1_date = November 1967
}}
}}


'''Aniakchak''' new article content ...
[[File:Aniakchak 3D.gif|thumb|300px|Aniakchak 3D.]]
'''Mount Aniakchak''' ({{lang-ru|Аниакчак}}) is a 3,600-year-old volcanic<ref name="SI">{{cite gvp | vn = 312090 | name = Aniakchak | accessdate = 2009-01-19}}</ref> [[caldera]] approximately {{convert|10|km|mi|0|sp=us}} in diameter, located in the [[Aleutian Range]] of [[Alaska]], [[United States of America|United States]]. Although a [[stratovolcano]] by composition, the pre-existing mountain collapsed in a major eruption forming the caldera.<ref name="wood">{{Cite book |url=https://books.google.com/books?id=eyDRib-FJh4C&dq=aniakchak%20stratovolcano&pg=PA59 |title=Volcanoes of North America : United States and Canada |date=1992 |publisher=Cambridge University Press |isbn=9780521438117 |edition=1st pbk. |location=Cambridge [England] |pages=59 and 60 |oclc=27910629}}</ref> The area around the volcano is the [[Aniakchak National Monument and Preserve]], maintained by the [[National Park Service]]. In November 1967, Aniakchak Caldera was designated as a [[National Natural Landmark]] by the National Park Service.<ref>{{Cite web|url=https://www.nps.gov/subjects/nnlandmarks/site.htm?Site=ANCR-AK|title=National Natural Landmarks - National Natural Landmarks (U.S. National Park Service)|website=www.nps.gov|language=en|access-date=2019-03-20}}</ref>


==Eruptive history==
== Geology ==
Little is known about the ancestral ([[Pleistocene]]) Aniakchak. The volcanic center has been active for at least 850,000 years.<ref name=":2">{{Cite journal |last1=Neal |first1=Christina A. |last2=McGimsey |first2=Robert G. |last3=Miller |first3=Thomas P. |last4=Riehle |first4=James R. |last5=Waythomas |first5=Christopher F. |date=2000 |title=Preliminary volcano-hazard assessment for Aniakchak Volcano, Alaska |journal=Professional Paper |series=Open-File Report |doi=10.3133/ofr00519 |issn=2331-1258|doi-access=free }}</ref> It was a moderate-sized composite volcano consisted of [[Basalt|basaltic]] [[andesite]] to [[dacite]] [[lava flow]]s and fragmental rocks erupted in [[Vulcanian eruption|Vulcanian]], [[Strombolian eruption|Strombolian]] and [[Effusive eruption|effusive]] styles.<ref name="SI" /><ref name=":0">{{Cite journal |last1=Bacon |first1=Charles R. |last2=Neal |first2=Christina A. |last3=Miller |first3=Thomas P. |last4=McGimsey |first4=Robert G. |last5=Nye |first5=Christopher J. |date=2014 |title=Postglacial eruptive history, geochemistry, and recent seismicity of Aniakchak volcano, Alaska Peninsula |journal=U.S. Geological Survey Professional Paper 1810, 74 P. |doi=10.3133/pp1810 |issn=2330-7102|doi-access=free }}</ref> The width of Birthday Creek valley suggests the possible existence of a small late Pleistocene caldera.<ref name=":0" /> Postglacial ([[Holocene]]) Aniakchak produced two major [[ignimbrite]]-forming eruptions, Aniakchak I and Aniakchak II.<ref name=":0" /><ref name=":1">{{Cite journal |last1=Miller |first1=Thomas P. |last2=Smith |first2=Robert L. |date=1987 |title=Late Quaternary caldera-forming eruptions in the eastern Aleutian arc, Alaska |url=http://dx.doi.org/10.1130/0091-7613(1987)15<434:lqceit>2.0.co;2 |journal=Geology |volume=15 |issue=5 |pages=434 |doi=10.1130/0091-7613(1987)15<434:lqceit>2.0.co;2 |issn=0091-7613}}</ref>


=== Pre-caldera history ===
=== Composition ===
Aniakchak I, dated between 9,500 and 7,000 year [[Before Present|BP]], was formed by andesite pyroclastic flows during one or a few closely spaced eruptions.<ref name=":0" /> The volume of Aniakchak I is unknown,<ref name=":1" /> and it remains unclear whether a caldera was formed.<ref name=":0" />


[[Orthopyroxene]] is the main [[phenocryst]] in tephra, with [[amphibole]], [[hornblende]] and [[clinopyroxene]] less common.{{sfn|Begét|Mason|Anderson|1992|p=51}}
Series of closely spaced eruptions occurred around 7,000 year BP, depositing extensive dacite and [[rhyodacite]] Plinian [[pumice]] fall and intraplinian welded rhyodacite ignimbrite, known as Black Nose Pumice Fall.<ref name=":0" />


== Eruption history ==
At least 20 explosive eruptions occurred at Aniakchak in postglacial time before the Aniakchak II eruption.<ref name=":2" />


An eruption 4,400-10,000 years ago produced an ashflow.{{sfn|Begét|Mason|Anderson|1992|p=53}}
=== Aniakchak II ===
In 1629 BC,<ref name=":4">{{cite journal |author=McAneney |first1=Jonny |last2=Baillie |first2=Mike |year=2019 |title=Absolute tree-ring dates for the Late Bronze Age eruptions of Aniakchak and Thera in light of a proposed revision of ice-core chronologies |journal=Antiquity |volume=93 |issue=367 |pages=99–112 |doi=10.15184/aqy.2018.165 |doi-access=free}}</ref><ref name=":5">{{Cite journal |last1=Pearson |first1=Charlotte |last2=Sigl |first2=Michael |last3=Burke |first3=Andrea |last4=Davies |first4=Siwan |last5=Kurbatov |first5=Andrei |last6=Severi |first6=Mirko |last7=Cole-Dai |first7=Jihong |last8=Innes |first8=Helen |last9=Albert |first9=Paul G |last10=Helmick |first10=Meredith |date=2022-04-29 |title=Geochemical ice-core constraints on the timing and climatic impact of Aniakchak II (1628 BCE) and Thera (Minoan) volcanic eruptions |journal=PNAS Nexus |volume=1 |issue=2 |doi=10.1093/pnasnexus/pgac048 |issn=2752-6542|doi-access=free }}</ref><ref name=":6">{{Cite journal |last1=Sinnl |first1=Giulia |last2=Winstrup |first2=Mai |last3=Erhardt |first3=Tobias |last4=Cook |first4=Eliza |last5=Jensen |first5=Camilla Marie |last6=Svensson |first6=Anders |last7=Vinther |first7=Bo Møllesøe |last8=Muscheler |first8=Raimund |last9=Rasmussen |first9=Sune Olander |date=2022-05-24 |title=A multi-ice-core, annual-layer-counted Greenland ice-core chronology for the last 3800 years: GICC21 |url=https://cp.copernicus.org/articles/18/1125/2022/ |journal=Climate of the Past |language=English |volume=18 |issue=5 |pages=1125–1150 |doi=10.5194/cp-18-1125-2022 |issn=1814-9324 |doi-access=free }}</ref> this voluminous ignimbrite-forming eruption created the modern Aniakchak caldera and had a profound global climatic impact.<ref name=":0" /><ref name=":4" /> This eruption produced rhyodacite [[Plinian eruption|Plinian]] pumice fall followed by highly mobilized rhyodacite and andesite ignimbrites.<ref name=":0" /><ref name=":3">Dreher, S.T., 2002, The physical volcanology and petrology of the 3400 yBP caldera-forming eruption of Aniakchak volcano, Alaska: ''Fairbanks, University of Alaska Fairbanks, Ph.D. dissertation.''</ref> The ignimbrite extends up to 80 km from the caldera and fills adjacent valleys to a thickness of up to 75 m. As the ignimbrite entered the [[Bering Sea]], it generated a [[tsunami]] that reached a height of 15 m above mean [[High-tide|high tide]] along the northern [[Bristol Bay]] coastline of Alaska.<ref>{{Cite journal |last1=Browne |first1=B.L. |last2=Neal |first2=C.A. |last3=Bacon |first3=C.R. |date=2022 |title=The ~400 yr B.P. eruption of Half Cone Volcano, a post-caldera composite cone within Aniakchak caldera, Alaska Peninsula |journal=Alaska Division of Geological & Geophysical Surveys Professional Report 126, 60 P |doi=10.14509/30839|doi-access=free }}</ref>


=== Aniakchak II eruption ===
The initial phase of Aniakchak II involved the eruption of rhyodacite and the formation of a Plinian column, which rapidly transitioned into the production of [[Pyroclastic flow|pyroclastic flows]]. The eruption then proceeded with the release of mixed rhyodacite-andesite pyroclastic flows, fed by collapsed eruption columns and characterized by a high mass-eruption rate. The final phase erupted andesite pyroclastic flows, fed by low eruption columns. It was during this andesite phase that the collapse of the caldera occurred.<ref name=":0" /><ref name=":3" /> The eruption produced a minimum of {{Convert|14|km3|mi3|abbr=on}} [[dense-rock equivalent]] (DRE) of rhyodacite and {{Convert|13|km3|mi3|abbr=on}} DRE of andesite as ignimbrite, amounting to a total of {{Convert|27|km3|mi3|abbr=on}} DRE. This is a minimum estimate as it does not include the intracaldera deposits.<ref name=":0" /><ref name=":3" />


An [[eruption column]] more than {{convert|25|km}} may have risen over the volcano.{{sfn|Begét|Mason|Anderson|1992|p=54}}
The identification of Aniakchak II glass shards that correspond to an acidic layer, along with the precise correlation between [[ice core]] acidic layers and [[Dendroclimatology|tree ring growth minima]], enabled the determination of the eruption's timing to be narrowed down to the years 1629–1628 BC in the Greenland Ice Core Chronology 2021 (GICC21).<ref name=":4" /><ref name=":5" /><ref name=":6" />


The Aniakchak II eruption is one of the largest [[Holocene]] eruptions in North America,{{sfn|Begét|Mason|Anderson|1992|p=54}} comparable with the 1912 [[Katmai]] and early Holocene [[Mount Mazama]] eruptions.{{sfn|Begét|Mason|Anderson|1992|p=53}} It yielded more than {{convert|50|km3}} in [[pyroclastic flow]]s and tephra.{{sfn|Begét|Mason|Anderson|1992|p=54}}
It is estimated that {{Val|32|11}} million tonnes of sulfur was injected into the [[stratosphere]] during this eruption, making it one of the largest events of the Late Holocene.<ref name=":5" /> This massive release of sulfur led to the onset of a severe [[volcanic winter]] and caused significant environmental disruption.<ref name=":7">{{Cite journal |last1=Grudd |first1=Håkan |last2=Briffa |first2=Keith R. |last3=Gunnarson |first3=Björn E. |last4=Linderholm |first4=Hans W. |date=2000-09-15 |title=Swedish tree rings provide new evidence in support of a major, widespread environmental disruption in 1628 BC |journal=Geophysical Research Letters |language=en |volume=27 |issue=18 |pages=2957–2960 |doi=10.1029/1999GL010852|doi-access=free }}</ref><ref name=":8">{{Cite journal |last1=Helama |first1=Samuli |last2=Saranpää |first2=Pekka |last3=Pearson |first3=Charlotte L. |last4=Arppe |first4=Laura |last5=Holopainen |first5=Jari |last6=Mäkinen |first6=Harri |last7=Mielikäinen |first7=Kari |last8=Nöjd |first8=Pekka |last9=Sutinen |first9=Raimo |last10=Taavitsainen |first10=Jussi-Pekka |last11=Timonen |first11=Mauri |last12=Uusitalo |first12=Joonas |last13=Oinonen |first13=Markku |date=2019 |title=Frost rings in 1627 BC and AD 536 in subfossil pinewood from Finnish Lapland |url=https://linkinghub.elsevier.com/retrieve/pii/S0277379118308357 |journal=Quaternary Science Reviews |language=en |volume=204 |pages=208–215 |doi=10.1016/j.quascirev.2018.11.031|hdl=10138/324637 |hdl-access=free }}</ref> The impact of this eruption is evident in the widespread anomalies in tree growth observed during the years 1628–1627 BC. The effects of this event were felt across a vast expanse of the Northern Hemisphere and may have played a role in the conclusion of the Arctic Norwegian Stone Age.<ref name=":5" /><ref name=":7" /><ref name=":8" />


Various dating methods, mostly relying on [[radiocarbon]], have yielded ages of around 3,000-4,000 years for the eruption.{{sfn|Begét|Mason|Anderson|1992|p=53}}
=== Post-caldera history ===
Since then, more than 20 eruptions have occurred from vents on the caldera floor. Vent Mountain has been the source of numerous eruptions of ash, bombs, and lava flows since the caldera formed. From 1500 BC to AD 1000 four lava domes were extruded on the caldera floor. Textural evidence shows that these lava-dome eruptions occurred beneath Ancient Surprise Lake which was as deep as 100m. Ancient Surprise Lake drained catastrophically before about AD 1000. (Surprise Lake (Aniakchak's crater lake) is now about 2.75 km2 (680 acres) in area and up to 19.5&nbsp;m (64.0&nbsp;ft) deep.) Before or immediately after this draining, explosive eruptions of andesitic magma produced a cluster of three tuff cones in the southeast part of the caldera.


The tephra fell north of the volcano, forming an elongated fallout deposit{{sfn|Begét|Mason|Anderson|1992|p=52}} extending across western Alaska, including the [[Alaska Peninsula]], [[Bristol Bay]], the [[Kuskokwim River|Kuskokwim]] and [[Yukon River Delta]]s, [[Norton Sound]] and the [[Seward Peninsula]].{{sfn|Begét|Mason|Anderson|1992|p=55}} It reaches a thickness of {{convert|1|cm}} {{convert|1500|km}} from the vent.{{sfn|Begét|Mason|Anderson|1992|p=51}}
Around AD 1500, during one of the most violent events in recent history at Aniakchak, an estimated 0.75 to 1.0 km3 of material destroyed a preexisting edifice at Half Cone and flooded most of the caldera floor with pyroclastic flows, surges, and fallout many meters thick. During the final phase of this eruption, a lava flow filled the basin formed during the collapse of Half Cone.


Tephra has been found at [[Chignik Bay]],{{sfn|Begét|Mason|Anderson|1992|p=54}} [[Cape Espenberg]] and [[Whitefish Lake]] on the [[Seward Peninsula]] (western Alaska){{sfn|Begét|Mason|Anderson|1992|p=51}}
Several more recent prehistoric eruptions occurred in the summit crater and along the south flank of Vent Mountain producing a field of blocky [[dacite]] lava flows against the south wall of the caldera. Minor eruptions immediately west and east of Vent Mountain produced a small scoria cone (Blocky Cone) and two maar craters (now water-filled) along the base of the southeast caldera wall.


The Aniakchak II eruption took place during the 17th century BC, an era with numerous volcanic eruptions; other volcanoes that erupted at that time are [[Mount St. Helens]], [[Vesuvius]] and in particular the [[Minoan eruption]] of [[Santorini]].{{sfn|Begét|Mason|Anderson|1992|p=55}}
European-descended geologists discovered the volcano in 1922.


== References ==
The volcano's only eruption in modern recorded history occurred in 1931. The [[Society of Jesus|Jesuit]] "Glacier Priest", Father [[Bernard Hubbard]], made record of it: "A small but impressive explosion pit was added to the pockmarked caldera floor that year. Many thousands of tons of ash lay strewn within the caldera and scattered up to 40 miles away over the small villages".<ref>"Aniakchak National Monument & Preserve", pulled from [http://www.ohranger.com/aniakchak/natural-world chranger.com], 3 June 2011.</ref>
{{Reflist}}


== Human history ==
=== Sources ===
{{refbegin}}
The caldera-forming eruptions of ~3,700 years ago had a significant effect on the regional landscape, and on the entire range of plant and animal life over a broad area. Indeed, the eruption has been implicated in widespread impacts on human populations across the whole of western Alaska.<ref>{{Cite book|title=The role of ecological barriers in the development of cultural boundaries during the later Holocene of the central Alaska Peninsula|last=VanderHoek|first=Richard|publisher=PhD Dissertation in Anthropology, University of Illinois at Urbana-Champaign|year=2009|location=Urbana}}</ref> In the immediate vicinity of the volcano, the effects were so severe that people did not return to the region for another 2,000 years.<ref>{{Cite journal|last1=Barton|first1=Loukas|last2=Shirar|first2=Scott|last3=Jordan|first3=James W.|date=March 2018|title=Holocene Human Occupation of the Central Alaska Peninsula|journal=Radiocarbon|language=en|pages=367–382|doi=10.1017/rdc.2018.2|issn=0033-8222|volume=60|issue=2|doi-access=}}</ref> Some scholars speculate that this eruption (and the subsequent devastation) may have segregated people to the north and south of the volcano for long enough to drive the divergence between Aleutian and Eskimo (Inuit-Yupik) languages.<ref>{{Cite journal|last=Dumond|first=Don E.|date=2004|title=Volcanism and history on the northern Alaska Peninsula|journal=Arctic Anthropology|volume=41|issue=2|pages=112–125|doi=10.1353/arc.2011.0023|s2cid=130379617}}</ref>
<ref>{{cite journal |last1=Begét |first1=James |last2=Mason |first2=Owen |last3=Anderson |first3=Patricia |title=Age, Extent and Climatic Significance of the c. 3400 BP Aniakchak Tephra, Western Alaska, USA |journal=The Holocene |date=March 1992 |volume=2 |issue=1 |pages=51–56 |doi=10.1177/095968369200200106 |url=https://journals-sagepub-com.wikipedialibrary.idm.oclc.org/doi/abs/10.1177/095968369200200106 |language=en}}</ref>
{{refend}}


<!--- Categories --->
==Surprise Lake==
Surprise Lake within the caldera is the source of the [[Aniakchak River]], a [[List of National Wild and Scenic Rivers|National Wild River]].

[[File:Map of Alaska Peninsula Volcanoes.gif|250px|thumb|left|Map showing volcanoes of Alaska Peninsula.]]
[[File:AniakchakCrater.jpg|250px|thumb|left|Aniakchak Caldera]]{{clear|left}}

==See also==
* [[List of National Natural Landmarks]]
* [[List of volcanoes in the United States]]

==References==
{{reflist}}

==External links==
* [http://www.aktrekking.com/AKpen.html Alaska Peninsula Trek]
* [http://www.avo.alaska.edu/index.php Alaska Volcano Observatory]
* [http://pubs.usgs.gov/dds/dds-40/ Volcanoes of the Alaska Peninsula and Aleutian Islands-Selected Photographs]

{{authority control}}

{{DEFAULTSORT:Aniakchak, Mount}}
[[Category:Active volcanoes]]
[[Category:Aleutian Range]]
[[Category:Volcanic crater lakes]]
[[Category:Volcanoes of Lake and Peninsula Borough, Alaska]]
[[Category:National Natural Landmarks in Alaska]]
[[Category:Subduction volcanoes]]
[[Category:VEI-6 volcanoes]]
[[Category:Calderas of Alaska]]
[[Category:Volcanoes of Alaska]]
[[Category:Stratovolcanoes of the United States]]
[[Category:Holocene calderas]]
__INDEX__
__NEWSECTIONLINK__

Revision as of 16:14, 4 January 2024


Aniakchak new article content ...

Geology

Composition

Orthopyroxene is the main phenocryst in tephra, with amphibole, hornblende and clinopyroxene less common.[1]

Eruption history

An eruption 4,400-10,000 years ago produced an ashflow.[2]

Aniakchak II eruption

An eruption column more than 25 kilometres (16 mi) may have risen over the volcano.[3]

The Aniakchak II eruption is one of the largest Holocene eruptions in North America,[3] comparable with the 1912 Katmai and early Holocene Mount Mazama eruptions.[2] It yielded more than 50 cubic kilometres (12 cu mi) in pyroclastic flows and tephra.[3]

Various dating methods, mostly relying on radiocarbon, have yielded ages of around 3,000-4,000 years for the eruption.[2]

The tephra fell north of the volcano, forming an elongated fallout deposit[4] extending across western Alaska, including the Alaska Peninsula, Bristol Bay, the Kuskokwim and Yukon River Deltas, Norton Sound and the Seward Peninsula.[5] It reaches a thickness of 1 centimetre (0.39 in) 1,500 kilometres (930 mi) from the vent.[1]

Tephra has been found at Chignik Bay,[3] Cape Espenberg and Whitefish Lake on the Seward Peninsula (western Alaska)[1]

The Aniakchak II eruption took place during the 17th century BC, an era with numerous volcanic eruptions; other volcanoes that erupted at that time are Mount St. Helens, Vesuvius and in particular the Minoan eruption of Santorini.[5]

References

  1. ^ a b c Begét, Mason & Anderson 1992, p. 51.
  2. ^ a b c Begét, Mason & Anderson 1992, p. 53.
  3. ^ a b c d Begét, Mason & Anderson 1992, p. 54.
  4. ^ Begét, Mason & Anderson 1992, p. 52.
  5. ^ a b Begét, Mason & Anderson 1992, p. 55.

Sources

[1]


  1. ^ Begét, James; Mason, Owen; Anderson, Patricia (March 1992). "Age, Extent and Climatic Significance of the c. 3400 BP Aniakchak Tephra, Western Alaska, USA". The Holocene. 2 (1): 51–56. doi:10.1177/095968369200200106.
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