Ƙaramin fashewar Toba

**fashewa Toba** (wanda kuma ake kira Toba supereruption da Youngest Toba eruption) wani fashewar dutse ne wanda ya faru kusan shekaru 74,000 da suka gabata, a lokacin Late Pleistocene,  a shafin yanar gizon Lake Toba na yanzu, a Sumatra, Indonesia. Ita ce ta ƙarshe a cikin jerin akalla fashewar caldera guda huɗu a can, caldera da aka sani a baya ya samo asali kimanin shekaru miliyan 1.2 da suka gabata. Wannan, fashewar karshe, yana da ƙididdigar fashewar dutse wuta na 8, yana mai da shi mafi girman fashewar fashewar wuta a cikin Quaternary, kuma ɗaya daga cikin manyan fashewar da aka sani a Tarihin Duniya.

## Fitarwa

### Tarihin fashewar Toba
Ba a san ainihin ranar da fashewar ta faru ba, amma yanayin ajiyar toka ya nuna cewa ya faru ne a lokacin bazara na arewacin kasar saboda damina ce kawai ta iya ajiye tokar Toba a tekun Kudancin China .  Fashewar ta kasance mai yiwuwa kwanaki 9 zuwa 14.  Kwanan kwanan nan biyu na ƙayyadaddun ƙayyadaddun ƙayyadaddun argon-argon kwanan wata da fashewa zuwa 73,880 ± 320  da 73,700 ± 300 shekaru da suka wuce.  An kunna jikin magma daban-daban guda biyar a cikin ƴan ƙarni kaɗan kafin fashewar.   Faɗuwar ta fara ne da ƙarami da ƙayyadaddun faɗuwar iska kuma an bi ta kai tsaye da babban lokaci na kwararar wuta .  Lokacin ignimbrite yana da ƙananan maɓuɓɓugar ruwa,  amma ginshiƙan haɗin gwiwar da aka haɓaka a saman ɗigon pyroclastic ya kai tsayin  .  Matsalolin man fetur akan fitar da sulfur ya haifar da fa'ida daga  zuwa , ya danganta da kasancewar iskar sulfur daban a cikin ɗakin magma na Toba.   Ƙarshen ƙarshen ƙima shine saboda ƙarancin sulfur a cikin magma.  Rubuce-rubucen kankara sun ƙididdige fitar da sulfur akan tsari na 

### Sakamakon fashewar
Bill Rose and Craig Chesner of Michigan Technological University have estimated that the total amount of material released in the eruption was at least —about  of ignimbrite that flowed over the ground, and approximately  that fell as ash mostly to the west. However, as more outcrops become available, the most recent estimate of eruptive volume is  dense-rock equivalent (DRE), of which  was deposited as ash fall and  as ignimbrite, making this eruption the largest during the Quaternary period. Previous volume estimates have ranged from  to . Inside the caldera, the maximum thickness of pyroclastic flows is over . The outflow sheet originally covered an area of  with thickness nearly , likely reaching into the Indian Ocean and the Straits of Malacca. The air-fall of this eruption blanketed the Indian subcontinent in a layer of  ash, the Arabian Sea in , the South China Sea in , and Central Indian Ocean Basin in . Its horizon of ashfall covered an area of more than  in  or more thickness (~7.5% of the Earth's surface). In Sub-Saharan Africa, microscopic glass shards from this eruption are also discovered on the south coast of South Africa, in the lowlands of northwest Ethiopia, in Lake Malawi, and in Lake Chala. In South China, Toba tephras is found in Huguangyan Maar Lake.

Rushewar da ta biyo baya ta samar da caldera wanda ya cika da ruwa, ya haifar da Tafkin Toba. Tsibirin da ke tsakiyar tafkin an kafa shi ne ta hanyar resurgent dome.

### Tasirin yanayi

#### Yanayi a lokacin fashewar
Greenland Stadium 20 (GS20) wani abu ne mai sanyi na tsawon shekaru dubu a arewacin Tekun Atlantika wanda ya fara a lokacin fashewar Toba .  Lokacin farawar GS20 an sanya shi zuwa 74.0-74.2 kyr, kuma duk taron ya dauki kimanin shekaru 1,500. Yana da ɓangaren filin wasa na taron Dansgaard-Oeschger 20 (DO20), wanda aka saba bayyana shi ta hanyar raguwa ba zato ba tsammani a cikin ƙarfin juyawa na Atlantic meridional (AMOC). AMOC mai rauni ya haifar da dumama a Kudancin Tekun da Antarctica, kuma wannan asynchrony an san Sai dai seesaw na bipolar. Farawar taron sanyaya na GS20 ya dace da farkon taron dumama na Antarctic Isotope Maxima 19 (AIM19). GS20 an haɗa shi da fitar da kankara a cikin Arewacin Atlantic, don haka an kuma kira shi Heinrich stadium 7a. Abubuwan Heinrich sun fi tsayi, sanyi kuma suna da rauni AMOC a cikin Tekun Atlantika fiye da sauran filayen DO. Daga 74 zuwa 58 kyr, Duniya ta sauya daga matakin isotope na ruwa (MIS) 5 zuwa MIS mai kankara 4, yana fuskantar sanyaya da fadada kankara. Wannan canjin wani bangare ne na sake zagayowar interglacial-glacial na Pleistocene wanda bambance-bambance a cikin yanayin duniya suka haifar. Yanayin zafi na teku ya sanyaya da  ° C (1.6 ° F).  Matsayin teku ya fadi  m (200 .  Yankin kankara na Arewacin Hemisphere ya fara fadadawa sosai kuma ya wuce girman Ƙarshen Ƙarshen A gabashin Turai, Arewa maso gabashin Asiya da Cordillera na Arewacin Amurka. Kudancin Hemisphere glaciation ya girma har zuwa iyakarsa a lokacin MIS 4. Australasia, Afirka da Turai sun kasance suna da yanayin sanyi da busasshiyar yanayi.

## Manazarta