Ana kiranta glaciation shekarun kankara, shekarun kankara ko lokacin kankara wadannan lokuttan yanayin kasa suna faruwa ne a lokacin tsananin sanyi na yanayin duniya, wanda hakan kan kai ga daskarewar ruwa, da fadada shingen kankara da kuma bayyanar kankara na nahiyar. A cikin waɗannan lokuttan flora da fauna dole ne su dace da sabbin mahalli.
A cikin wannan labarin za mu gaya muku abin da manyan shekarun kankara suka kasance, menene halayen su, haddasawa da sakamakon su.
menene shekarun kankara
Zamani ne na tsawon lokaci (gaba ɗaya tsawaita: dubun-dubatar shekaru) waɗanda dole ne rayuwa ta dace da bushewa da yanayin sanyi ko halaka. Suna iya canza yanayin yanayin ƙasa, nazarin halittu da yanayin yanayin duniyar duniyar.
Za a iya raba shekarun kankara zuwa lokutan dusar ƙanƙara, lokutan ƙara sanyi, da lokutan tsaka-tsaki, lokutan sanyi, da yawan zafin jiki, duk da cewa har yanzu yana cikin ma'auni na yanayin sanyaya na duniya na dogon lokaci.
Duniya ta fuskanci glaciations da yawa lokaci-lokaci. na ƙarshe wanda ya fara shekaru 110.000 da suka wuce. An kiyasta cewa gaba dayan wayewarmu ta ci gaba kuma ta rayu a lokacin tsaka-tsakin lokaci wanda ya fara shekaru 10.000 da suka gabata.
tarihin kankara
Zamanin Ice Quaternary ya faru a lokacin Cenozoic Neogene. Ko da yake a halin yanzu kashi 10 cikin XNUMX na saman duniya ƙanƙara ne ke rufe shi, mun san cewa ba koyaushe haka lamarin yake ba. Gilashin glaciations a cikin tarihin ƙasa na duniya sun bar alamun da za a iya gane su, don haka a yau mun san manyan lokatai guda biyar, waɗanda sune:
- Huron Ice Age. Ya fara shekaru biliyan 2.400 da suka wuce kuma ya ƙare a zamanin Paleoproterozoic geological shekaru biliyan 2.100 da suka wuce.
- Sturtian-Varangian glaciation. Yana samun sunansa daga lokacin ƙananan zafin jiki na Neoproterozoic, wanda ya fara shekaru miliyan 850 da suka wuce kuma ya ƙare shekaru miliyan 635 da suka wuce.
- Andean-Sahara Glacier. Ya faru tsakanin shekaru miliyan 450 zuwa 420 da suka gabata, a cikin Paleozoic (Ordovician da Silurian), kuma shine mafi guntu da aka sani.
- Karoo Glacier. Ya fara shekaru miliyan 360 da suka wuce kuma ya ƙare shekaru miliyan 100 bayan haka, a cikin Paleozoic guda ɗaya (Carboniferous da Permian).
- Quaternary glaciation. Kwanan baya, wanda ya fara shekaru miliyan 2,58 da suka gabata a cikin lokacin Neogene na zamanin Cenozoic, zai ƙare yanzu.
Duniya wasan dusar ƙanƙara ce
Zaman kankara na duniya, superglacial ko "kwallon dusar ƙanƙara" na Duniya hasashe ne game da abin da ya faru a lokacin lokacin Neoproterozoic na ƙananan yanayin zafi, wanda a lokacin da an samar da glaciers ɗaya ko fiye a dukan duniya, wanda ya rufe dukan duniya tare da ƙanƙara mai yawa na ƙanƙara, kuma yana rage yawan zafin jiki zuwa -50 ° C.
An kiyasta cewa wannan al'amari (wanda aka tsara a zamanin Sturtian-Varangian Ice Age) ya shafe kusan shekaru biliyan 10, mafi girman shekarun kankara a tarihin duniya, kuma ya kai ga kusan bacewar rayuwa. Duk da haka, sahihancinsa lamari ne da ake ta muhawara a cikin al'ummar kimiyya.
Ageananan shekarun kankara
Sunan yana nufin lokacin sanyi mai tsanani da ya faru a duniya daga karni na XNUMX zuwa tsakiyar XNUMX. Wani lokacin zafi na musamman da aka sani da mafi kyawun yanayi na Tsakiyar Tsakiya (ƙarni na XNUMX zuwa XNUMX) ya ƙare.
Ba daidai ba ne glaciation, nisa daga gare ta, kuma a fannin ilimin kasa, yana da ɗan gajeren rayuwa. A kowane hali, an kasu kashi uku, wanda aka yi masa alama da raguwar zafin jiki mafi ƙanƙanta: 1650, 1770 da 1850.
sakamakon shekarun kankara
Glaciation yana haifar da wani nau'i na musamman na yazawa a cikin dutsen. Ana iya raba babban tasirin zamanin Ice zuwa kashi uku:
- Geology. Gilashin ya haifar da wani nau'i na musamman na zaizayar ƙasa a cikin duwatsu, ko dai ta hanyar sanyaya, ta hanyar matsewar ƙanƙara ko kuma ta yanayin yanayi, wanda ya haifar da wani yanayi na musamman a cikin duwatsun zamaninsa.
- Chemical. Abubuwan da ke haifar da dusar ƙanƙara suna kasancewa a matsayin dusar ƙanƙara ta dindindin a lokuta da yawa (kamar a saman manyan tsaunuka masu tsayi) saboda canje-canjen isotopic a cikin ruwa, yana mai da shi nauyi fiye da yadda aka saba. Wannan yana haifar da haɓakar ƙawancen ruwa da kuma narkewar zafin ruwa.
- Paleontology. Wadannan sauye-sauye masu tsauri a yanayin zafi da yanayin sau da yawa suna tare da ɓarkewar ɗimbin yawa, waɗanda ke samar da adadi mai yawa na kwayoyin halitta, suna samar da adadi mai yawa, kuma suna barin bayanan burbushin halittu masu yawa. Bugu da ƙari, dabbobin da ba su iya daidaitawa da sanyi suna gudu zuwa wurare masu zafi, suna haifar da matsuguni na dusar ƙanƙara da manyan motsin tarihin rayuwa.
Dalilan shekarun kankara
Abubuwan da ke haifar da shekarun kankara na iya zama daban-daban da kuma jayayya. Wasu ra'ayoyin sun nuna cewa sun samo asali ne saboda canje-canje a cikin yanayin yanayi wanda ke iyakance shigar da makamashin zafi daga rana, ko ƙananan canje-canje a cikin kewayar duniya.
A gefe guda, Yana iya zama saboda motsin faranti na tectonic: idan nahiyoyin suka kusanci juna, suna rufe sararin samaniya zuwa teku, cikinsa ya zama bushewa da zafi, yana rage magudanar ruwa. To sai dai kuma, da a ce kasashen nahiyoyin za su watsu su rabu, za a samu karin ruwa da za su yi sanyi da kuma kiyaye yanayin zafi a duniya.
kankara shekarun dabbobi
Dabbobin da suka tsira daga canje-canjen zamanin Ice kuma suka dace da rayuwa a cikin wuraren daskarewa sau da yawa suna da takamaiman halaye: kauri mai kauri da kitse wanda ke kare jikinsu daga sanyi a ciki, daidaitawar rayuwa zuwa sanyi da fari, da abinci mai kalori mai yawa. .
Duk da haka, ta hanyar kallon manyan nau'in dabba na zamanin ƙanƙara na ƙarshe, yana yiwuwa a fahimci takamaiman hanyoyin da kowane nau'in jinsuna ya amsa ga sanyi, kamar:
- Mai shaƙatawa. Giwaye masu sa'a sun saba da sanyi, kuma jikinsu yana lulluɓe da ulun ulu har tsawon mita ɗaya, kuma haƙoransu na iya murkushe harsashin ciyayi masu daskararre. Suna rayuwa har zuwa shekaru 80.
- Damisa mai tsayi. Wadannan maharbi masu karfi sun kasance gajarta, nauyi da kauri fiye da zakuna, masu tsayin daka mai tsawon santimita 18 wadanda za su iya bude muƙamuƙinsu a lokacin da suke cizon su 120, duk don kiyaye su a cikin filayen farauta da aka daskare a lokacin.
- karkanda masu ulu. Magabatan karkanda a yau, manyan jikinsu an lullube su da ulu kuma nauyinsu ya kai ton 4. Kahonsa da kwanyarsa sun fi ƙarfi kuma sun fi girma, kuma tana iya binne dusar ƙanƙara don neman abinci.
Ina fatan cewa tare da wannan bayanin zaku iya ƙarin koyo game da shekarun kankara daban-daban da halayensu.