Amurka ta tsakiya Volcanic Arc

Dutsen Volcanic na Amurka ta Tsakiya (wanda kuma  aka fi sani da CAVA) sune jerin tsaunuka ne na tsaunuka wanda ke tafiya daidai da gabar tekun Pacific na Isthmus ta Tsakiyar Amurka, daga Mexico zuwa Panama.  Wannan baka mai aman wuta, wanda ke da tsawon kilomita 1,100 (680 mi) an kafa shi ta wani yanki mai ƙarfi, tare da farantin Cocos da ke ƙarƙashin farantin Caribbean farantin Arewacin Amurka da farantin Volcanic na Panama ana yin rikodin ayyukan Volcanic a yankin Amurka ta Tsakiya tun daga Permian.    Dutsen tsaunuka da yawa suna yaduwa a cikin ƙasashe daban-daban na Amurka ta Tsakiya;  da yawa sun kasance masu aiki a zamanin da suka gabata, suna bambanta da ƙarfin ayyukansu bisa ga dalilai daban-daban.

 Yanayin tectonic 
An kafa CAVA ta hanyar rage faranti na Cocos da Nazca a ƙarƙashin faranti na Arewacin Amirka, Caribbean da Panama.   Tsarinsa yana da nau'i daban-daban, ta hanyar haɗuwa da gutsutsayen teku da na nahiyoyi.[Gazel et al.  (2021) ayyana yankuna huɗu na CAVA: ɓangarorin faranti na Arewacin Amurka (ɓawon nahiya), Yankin Suture na Guatemala (GSZ) (ɓawon nahiya), shingen nahiya na farantin Caribbean, da rukunin haɗin gwiwar Pacific (ɓawon teku).

Farantin tectonic Cocos yana gefen yammacin Amurka ta Tsakiya.  Ƙarshen yana gefen yamma na farantin tectonic na Caribbean kuma ana iya raba shi zuwa gwamnatoci daban-daban.  Waɗannan gwamnatocin ana shata su ne ta iyakar Costa Rica-Nicaragua kuma ana iya bambanta su da tarihin tectonic daban-daban na kowane yanki.  Yankin kudanci wani bangare ne na baka na magmatic, yayin da na arewa yana da alaƙa da tazara masu aiki da yawa.  Akwai nau'o'in kurakurai daban-daban a cikin kowace gwamnati kuma suna ƙara bambance tarihin yankin arewa da na kudu da juna.

 Tarihin yanayin ƙasa 
Rikodin magmatic na Amurka ta tsakiya ya fara da Permian-Triassic (~ 283-215 Ma) granites da gneisses na arc affinity, wanda aka kafa a gefen yammacin Pangea.  Kashi na biyu ya ƙunshi Jurassic-Berriasian na nahiyar rift volcanism, mai alaƙa da buɗewar proto-Caribbean da Gulf of Mexico.   Na uku bugun jini ya hada da calc-alkaline volcanism da intrusive duwatsu jere daga Aptian-Ypresian (~ 124-50 Ma) samuwa a cikin nahiyar slivers na Caribbean farantin, da MCOT da Santa Elena da Nicoya raka'a.   Tsakanin sassa na biyu da na uku, akwai tsibirin Jurassic-Cretaceous dutsen dutsen tsaunuka na asalin paleo-Pacific waɗanda suka shiga cikin GSZ da Mesquito Composite Oceanic Terrane (MCOT).  Buga na huɗu kawai yana cikin Sashin Talamanca na farantin Panama, na shekarun Maastrichtian-Bartonian (~ 71-39 Ma), na musamman tholeiitic.   Na biyar da na shida magmatic bugun jini (Oligocene-Pliocene da Quaternary) bayyana CAVA, duka a layi daya da tsakiyar Amurka Trench.

An rubuta wani lamari mai ban sha'awa na juyin halittar volcanic a Nicaragua, wanda ya fara ~ 130 Ma.  Nicaragua a zamanin yau tana da ɓawon nahiya a ɓangarenta na arewa (Patuca Block) wanda ke canzawa zuwa ɓawon teku (MCOT) har zuwa arewa maso yammacin Costa Rica ( Block Santa Elena, Nicoya Block).  Tsofaffin duwatsu masu aman wuta suna tsiro a cikin Patuca Block, tun daga tsakiyar Jurassic (~ 170 Ma).   Tsohuwar Arc na Nicaragua ya ƙunshi tsohuwar baka na Cretaceous-Eocene (~ 130-50 Ma), Oligocene-Miocene arc (~ 30-5 Ma) da gaban dutsen na kwanan nan.  Tsohuwar baka tana da ƙarin ƙayyadaddun calc-alkaline na acidic, inda Oligocene-Miocene arc ya kasance tsaka-tsaki zuwa abun da ke ciki na basaltic tholeiiic, kuma gaban dutsen mai aman wuta galibi basaltic tholeiitic ne a cikin abun da ke ciki.  Ba a fahimci abubuwan da ke haifar da waɗannan canje-canjen ba, amma wani bayani zai iya zama cewa katako ya fi girma a cikin rikice-rikice a lokacin tsohuwar baka, ko kuma narke zai iya kula da abubuwan da ba su da kyau..

Wannan hulɗar tectonic ta Caribbean-Cocos na iya ƙara yin bayani game da volcanism da tarihin ƙasa na yankin tun daga Miocene.  Duk da yake wallafe-wallafen da suka gabata sun nuna shekaru masu yawa don ƙaddamar da farantin Cocos, yanzu an yi imanin cewa wannan ƙaddamarwa ya fara ne tsakanin shekaru miliyan biyu da suka wuce da shekaru miliyan uku da suka wuce (tsakanin 2 Ma da 3 Ma) ko da yake yankin yana aiki da ilimin geologically tun a kalla 12 Ma, kamar yadda aka tabbatar da faranti da farantin iyaka ƙungiyoyi, da kuma subduction scarp [6] a cikin yankin.  An fahimci tazarar volcanism a tsakiyar Amurka tsakanin 12 Ma da 5 Ma.MacMillan, I., Gans, P. and Alvarado, G., 2004. Middle Miocene to present plate tectonic history of the southern Central American Volcanic Arc. Tectonophysics, 392(1-4), pp.325-348.Morell, K., Kirby, E., Fisher, D. and van Soest, M., 2012. Geomorphic and exhumational response of the Central American Volcanic Arc to Cocos Ridge subduction. Journal of Geophysical Research: Solid Earth, 117(B4)

Bugu da ƙari kuma, ƙaddamar da farantin tectonic na Cocos da kansa ba a tunanin shi ne abin da ya haifar da wasu canje-canje na volcanism da ke da alaka da Arc Volcanic na Amurka ta Tsakiya;  yayin da ƙaddamar da Cocos Ridge wani lamari ne mai ci gaba wanda ya yi tasiri ga volcanism a Amurka ta tsakiya, ƙaddamar da Coiba Ridge - wani microplate a yankin - ana tunanin shine abin da ya haifar da shi [1] wanda ya haifar da canje-canje a ayyukan volcanic a zamanin da.  A taƙaice, hulɗar faranti masu yawa na tectonic - wato Cocos, Caribbean, Arewacin Amirka, da Coiba. MacMillan, I., Gans, P. and Alvarado, G., 2004. Middle Miocene to present plate tectonic history of the southern Central American Volcanic Arc. Tectonophysics, 392(1-4), pp.325-348.  farantin - a cikin shekaru miliyoyin da suka gabata ya taimaka wajen sauƙaƙa ci gaba da wanzuwar Arc na Volcanic na Amurka ta Tsakiya, yana rinjayar tarihin tectonic na yankin.

 Bayani na yanki na zamani 
Ƙarƙashin Ƙarƙashin Ƙarƙashin Ƙarƙashin Ƙasa ta Amirka ya ƙunshi ɗaruruwan tsaunuka na tsaunuka, ciki har da stratovolcanoes, composite volcanoes, calderas, da lava domes.  Daga hangen nesa, toka ya fado, toka yana gudana, da ajiyar tephra sun zama ruwan dare a ko'ina cikin yankin. An yi amfani da Dating na Carbon da argon isotope har zuwa kwanan wata waɗannan adibas zuwa Quaternary, kuma ana zargin cewa da yawa daga cikin waɗannan tsaunuka sun kasance suna aiki akai-akai tsawon shekaru 200,000 da suka gabata.Rose, W., Conway, F., Pullinger, C., Deino, A. and McIntosh, W., 1999. An improved age framework for late Quaternary silicic eruptions in northern Central America. Bulletin of Volcanology, 61(1-2), pp.106-120.

Wasu tsaunuka a yankin sun ma haifar da fashewar abubuwa masu fashewa a baya bayan nan, ciki har da fashewar dutsen Santa Maria a Guatemala a ranar 25 ga Oktoba, 1902.  Wannan fashewar Plinian ta haura sama da toka mai tsawon kilomita 20 kusan kilomita talatin zuwa sama.  Yawancin wannan ash an yi shi da kyau, wanda girmansa bai wuce milimita 2 ba..Williams, S. and Self, S., 1983. The October 1902 plinian eruption of Santa Maria volcano, Guatemala. Journal of Volcanology and Geothermal Research, 16(1-2), pp.33-56.

Hakazalika, Cerro Negro, dutse mai tsauri mai tsayin mita 250 a arewa maso yammacin Nicaragua, ya barke a 1971, 1992, da 1995. Fashewar fashewar guda biyu, wadanda suka faru a cikin 1990s, suna da nau'ikan sihiri iri ɗaya ga juna, duka basaltic. Duk da haka, kamar yadda ruwa da carbon dioxide da ke cikin kowane fashewa ya bambanta - tare da fashewar farko yana da matakan carbon dioxide da tururin ruwa, da kuma fashewar fashewar da ke lalata yawancin abubuwan da ke faruwa[1] - a bayyane nau'i daban-daban na fashewa ya faru.

Sauran tsaunukan tsaunuka a Amurka ta tsakiya sun hada da Santa Ana, Izalco, da San Salvador volcanoes, Nicaraguan Masaya volcanoes, da Costa Rica Miravalles, Irazu, da Poás volcanoes. Mutane da yawa suna ci gaba da aiki lokaci-lokaci har zuwa yau, kuma da alama za su ci gaba da yin aiki a nan gaba, yayin da tsarin ƙasa da tectonic ke ci gaba da tsara yankin.
Rukuni:Shafuka masu fassarorin da ba'a duba ba