Yankin kankara

A cikin ilimin glaciology, **takardar kankara**, wanda kuma aka sani da **glacier na nahiyar**,  wani nau'i ne na kankara mai yawa wanda ke kewaye da ƙasa kuma ya fi    .  Saitunan ƙanƙara na yanzu shine takardar kankara ta Antarctic da takardar kankara ta Greenland . Gilashin kankara sun fi kankara girma ko glaciers mai tsayi. Yawan kankara da ke rufe kasa da 50,000&nbsp;km2 ana kiranta hular kankara . Ƙunƙarar ƙanƙara za ta ciyar da jerin glaciers kewaye da kewayenta.

Kodayake farfajiyar tana da sanyi, tushe na kankara gabaɗaya ya fi zafi saboda zafi na geothermal. A wurare, narkewa yana faruwa kuma ruwan da ya narke yana shafa kan kankara don ya gudana da sauri. Wannan tsari yana samar da tashoshin da ke gudana da sauri a cikin kankara - waɗannan raƙuman kankara ne.&nbsp;

Ko da tsaunuka masu tsawo suna ci gaba da motsi yayin da kankara ke gudana a hankali daga tsakiya na tsakiya, wanda shine mafi tsayi na kankara, kuma zuwa gefen. Yankin kankara yana da ƙasa a kusa da tudu amma yana ƙaruwa sosai a gefen.

Karin yanayin iska na duniya saboda canjin yanayi yana ɗaukar kusan shekaru 10,000 don yaduwa kai tsaye ta cikin kankara kafin su rinjayi yanayin gado, amma suna iya samun tasiri ta hanyar kara narkewar ƙasa, samar da tabkuna masu yawa. Wadannan tabkuna na iya ciyar da ruwa mai dumi zuwa tushe na kankara kuma suna sauƙaƙa motsi na kankara.

A cikin lokutan geologic da suka gabata (lokacin ƙanƙara) akwai wasu kankara. A lokacin Last Glacial Period a Last Glacial Maximum, Laurentide Ice Sheet ya rufe yawancin Arewacin Amurka. A cikin wannan lokacin, kankara na Weichselian ya rufe Arewacin Turai kuma Patagonian Ice Sheet ya rufe kudancin Kudancin Amurka.

## Bayani na gaba ɗaya

An ice sheet is a body of ice which covers a land area of continental size - meaning that it exceeds 50,000&nbsp;km2. The currently existing two ice sheets in Greenland and Antarctica have a much greater area than this minimum definition, measuring at 1.7 million km2 and 14 million km2, respectively. Both ice sheets are also very thick, as they consist of a continuous ice layer with an average thickness of . This ice layer forms because most of the snow which falls onto the ice sheet never melts, and is instead compressed by the mass of newer snow layers.

Wannan tsari na ci gaban kankara har yanzu yana faruwa a zamanin yau, kamar yadda za'a iya gani a fili a cikin misalin da ya faru a yakin duniya na biyu. Wani jirgin yaki na Lockheed P-38 Lightning ya fadi a Greenland a 1942. An dawo da shi ne kawai bayan shekaru 50. A lokacin, an binne shi a ƙarƙashin 81 m (268 feet) na kankara wanda ya samo asali a wannan lokacin.

## Ƙarfin hali

### Gudun kankara

Ko da tsaunuka masu tsawo suna ci gaba da motsi yayin da kankara ke gudana a hankali daga tsakiya na tsakiya, wanda shine mafi tsayi na kankara, kuma zuwa gefen. Yankin kankara yana da ƙasa a kusa da tudu amma yana ƙaruwa sosai a gefen. Wannan bambanci a cikin gangara yana faruwa ne saboda rashin daidaituwa tsakanin tarin kankara a cikin tsakiya na tsakiya da ƙananan tarin, da kuma mafi girma, a gefen. Wannan rashin daidaituwa yana ƙara damuwa a kan kankara har sai ya fara gudana. Saurin kwarara da lalacewa za su karu yayin da aka kusanci layin daidaitawa tsakanin waɗannan matakai biyu. Wannan motsi yana motsawa ta hanyar nauyi amma ana sarrafa shi ta hanyar zafin jiki da ƙarfin tushe na kankara. Yawancin matakai suna canza waɗannan dalilai guda biyu, wanda ke haifar da hauhawar aiki tare da tsawon lokaci na rashin aiki, a kan ma'auni na lokaci daga sa'a (watau kwararar ruwa) zuwa karni (Milankovich cycles). 

A kan sa'a-da-sa'a, ana iya daidaita motsi na kankara ta hanyar aikin ruwa. Za'a iya jin tasirin sautin ruwa na 1 m har zuwa kilomita 100 daga teku. A lokacin manyan raƙuman ruwa, rafin kankara zai kasance kusan tsaye na sa'o'i a lokaci guda, kafin hawan kusan ƙafa ɗaya a ƙasa da awa ɗaya, bayan hawan ruwa mai yawa; lokacin da ya tsaya ya riƙe har sai wani hawan ruwa zuwa tsakiyar ko ƙarshen hawan ruwa. A lokacin da ake amfani da shi, wannan hulɗar ba ta da kyau, kuma a maimakon haka yana faruwa kusan kowane sa'o'i 12.&nbsp;&nbsp;

Karin yanayin iska na duniya saboda canjin yanayi yana ɗaukar kusan shekaru 10,000 don yaduwa kai tsaye ta cikin kankara kafin su rinjayi yanayin gado, amma suna iya samun tasiri ta hanyar kara narkewar ƙasa, samar da tabkuna masu yawa. Wadannan tabkuna na iya ciyar da ruwa mai dumi zuwa tushe na kankara kuma suna sauƙaƙa motsi na kankara. Tafkunan da ke da diamita fiye da ~ 300 m suna iya ƙirƙirar rami mai cike da ruwa zuwa kankara / gado. Lokacin da waɗannan raguwa suka samo asali, duk abubuwan da ke cikin tafkin (mai ɗan dumi) na iya kaiwa ga tushe na kankara a cikin sa'o'i 2-18 - mai da gado kuma ya sa kankara ya tashi. Ruwa da ya kai ga gado na kankara na iya daskarewa a can, yana ƙara kauri na kankara ta hanyar tura shi sama daga ƙasa

## Manazarta