Ƙarƙashin kankara

Babban kankara shine ainihin samfurin da aka cire daga kankara ko dutsen kankara. Tun da yake kankara ta samo asali ne daga haɓakar dusar ƙanƙara ta shekara-shekara, ƙananan yadudduka sun tsufa fiye da na sama, kuma ƙirar kankara tana ƙunshe da kankara da aka kafa a cikin shekaru da yawa. Ana hako layin tare da magunguna na hannu (don ramuka masu zurfi) ko kuma motsa jiki; suna iya kaiwa zurfin fiye da mil biyu (3.2 km), kuma suna dauke da kankara har zuwa shekaru 800,000.&nbsp;

Za'a iya amfani da kaddarorin jiki na kankara da kayan da aka kama a ciki don sake gina yanayi a kan shekarun tsakiya. Adadin isotopes daban-daban na isotopes na oxygen da hydrogen suna ba da bayani game da Yanayin zafi na dā, kuma ana iya nazarin iska da ke cikin ƙananan kumfa don tantance matakin iskar gas kamar carbon dioxide. Tunda zafi yana gudana a cikin babban kankara mai saurin gaske, zafin jiki na borehole wani alama ne na zafin jiki a baya. Ana iya haɗa wannan bayanan don samun samfurin yanayi wanda ya fi dacewa da duk bayanan da ke akwai.

Rashin tsabta a cikin ƙwayoyin kankara na iya dogara da wuri. Yankunan bakin teku sun fi haɗawa da kayan asalin ruwa, kamar su gishiri na teku. Greenland ice cores ya ƙunshi yadudduka na ƙurar da iska ta hura wanda ke da alaƙa da sanyi, lokutan bushewa a baya, lokacin da iska ta share hamada mai sanyi. Abubuwan rediyo, ko dai na asali ko kuma wanda aka kirkira ta hanyar gwajin nukiliya, ana iya amfani da su don kwanan wata kankara. Wasu abubuwan da suka faru na dutsen wuta waɗanda suka isa su aika kayan aiki a duniya sun bar sa hannu a cikin ƙwayoyin daban-daban waɗanda za a iya amfani da su don daidaita ma'aunin lokaci.

An yi nazarin ƙwayoyin kankara tun farkon karni na 20, kuma an hako ƙwayoyin da yawa sakamakon Shekarar Geophysical ta Duniya (1957-1958). An kai zurfin sama da mita 400, rikodin da aka tsawaita a cikin shekarun 1960 zuwa mita 2164 a Tashar Byrd a Antarctica. Ayyukan hako kankara na Soviet a Antarctica sun haɗa da shekaru da yawa na aiki a Tashar Vostok, tare da zurfin zurfin ya kai 3769 m. An kammala wasu zurfin zurfi a cikin Antarctic a cikin shekaru, gami da aikin West Antarctic Ice Sheet, da kuma ƙwayoyin da British Antarctic Survey da International Trans-Antarctic Scientific Expedition suka gudanar. A Greenland, jerin ayyukan hadin gwiwa sun fara ne a cikin 1970s tare da Greenland Ice Sheet Project; akwai ayyukan bin diddigin da yawa, tare da kwanan nan, East Greenland Ice-Core Project, da farko ana sa ran kammala zurfin tushe a gabashin Greenland a cikin 2020 amma tun lokacin an jinkirta.

## Tsarin kankara da ƙwayoyin

Tushen ƙanƙara ginshiƙi ne a tsaye ta cikin glacier, yana yin samfurin yadudduka waɗanda suka samo asali ta hanyar zagayowar dusar ƙanƙara da narke kowace shekara.  Yayin da dusar ƙanƙara ke taruwa, kowane Layer yana danna ƙananan yadudduka, yana sa su yi girma har sai sun zama fir . Firn ba shi da yawa don hana iska daga tserewa; amma da yawansu ya kai 830&nbsp;kg/m 3 ya juya ya zama kankara, kuma iskar da ke cikin tana rufe ta zama kumfa da ke daukar nau'in yanayi a lokacin da kankara ta samu.  Zurfin abin da wannan ke faruwa ya bambanta da wuri, amma a cikin Greenland da Antarctic ya tashi daga 64.&nbsp;m zuwa 115&nbsp;m.  Saboda yawan saukar dusar ƙanƙara ya bambanta daga wuri zuwa wuri, shekarun firn lokacin da ya juya zuwa kankara ya bambanta da yawa. A sansanin Summit a Greenland, zurfin yana da 77 m kuma kankara yana da shekaru 230; A Dome C a Antarctica zurfin shine 95 m kuma shekaru 2500.  Yayin da ƙarin yadudduka ke haɓaka, matsa lamba yana ƙaruwa, kuma a kusan 1500&nbsp;m tsarin lu'ulu'u na kankara yana canzawa daga hexagonal zuwa cubic, yana barin kwayoyin iska su matsa cikin lu'ulu'u masu siffar sukari kuma su samar da clathrate . Kumfa suna ɓacewa kuma ƙanƙara ta zama mafi m. 

ƙafa biyu ko uku na dusar ƙanƙara na iya zama ƙasa da ƙafa ɗaya na kankara. Nauyin da ke sama yana sa zurfin kankara ya yi tsayi kuma ya gudana waje. Ice ya ɓace a gefen kankara zuwa kankara, ko zuwa narkewar bazara, kuma siffar kankara gaba ɗaya ba ta canza sosai tare da lokaci. Gudun waje na iya karkatar da yadudduka, don haka yana da kyau a hako zurfin kankara a wuraren da akwai kadan. Ana iya samun waɗannan ta amfani da taswirar layin kwarara.

## Manazarta