Kwiplanethi yethu kunezixuku ezinkulu zeqhwa ezisibekela izingongolo ezisenyakatho naseningizimu. Leli qhwa alikho olwandle kuphela kodwa futhi litholakala nasezintabeni. Lezi zingqimba zeqhwa zaziwa njenge izinguzunga zeqhwa. Lapho lezi zinguzunga zeqhwa zifinyelela ubukhulu obukhulu kangangokuba zivame ukumboza izindawo eziphelele nezinabanzi, ziyabizwa izimbotshana zeqhwa elisendaweni emincane.
Kulesi sihloko sizokutshela zonke izici, ukubaluleka, amandla alezi zinhlayiya ezisezindaweni ezibandayo nokuthi kuzokwenzekani uma zonke lezi zigaxa zeqhwa zigcina zincibilikile.
Ukwakheka kwezinguzunga zeqhwa
Ukwenza indlela yamakhemikhali asezindaweni ezibandayo, okokuqala kudingekile ukwazi ukuthi izingqimba zeqhwa zakhiwa kanjani ukuze zisabalale ngendlela yokuthi ekugcineni zakhe isicoco se-polar. Konke ukumbozwa kweqhwa okusabalale ngesikhathi sokugcina i-glaciation noma i-ice age yakha izinguzunga zeqhwa. Lezi zinguzunga zeqhwa zibaluleke kakhulu njengama-erosive agents kanye nabakhi bokusiza, inhlabathi nezwe.
Esinye isizathu sokuthi kungani zibalulekile yingoba zingumthombo omkhulu wamanzi ahlanzekile emhlabeni. Kunezinto eziningi eziphilayo ezisizakala ngamanzi ancibilikile ehlobo lamaqhwa eqhwa ukuze ziqhubeke ziphila, zizalane noma zenze indawo yazo yemvelo yokuhlala.
Lezi zinguzunga zeqhwa zakhiwa ngokuqongelela, unyaka nonyaka, iqhwa eliwela ngaphansi nasemithambekeni yezigodi. Zitholakala ezindaweni eziphakeme zezintaba. Ubukhulu bungafinyelela ingxenye enkulu uma iqhwa elilahlekile ngenxa yokuncibilika ehlobo lingaphansi kwalelo eliqongelela ngenkathi yeqhwa.
Isisindo esihlanganisiwe saleli qhwa senziwa ngoba ukuwa ngakunye kweqhwa kucindezelwa kuleso ebesifakwe ngaphambilini phambilini. Uma ukushisa kokuncibilika kuphumelela ekuncibilikiseni iqhwa, kuzolibangela ukuthi likhuluphale bese liqala ukuya phansi kwesigodi.
Ubuningi beqhwa kuvame ukukhuphuka ngokujula njengoba kunenani elikhulu leqhwa endaweni ngayinye, libe lihlangene ngokwengeziwe. Leli phunga abanalo liyisisekelo senguzunga yeqhwa futhi ligeleza sengathi liwuketshezi. Ngaphakathi kweqhwa lihamba ngokushesha kunezindawo ezisemaceleni, ngakho-ke kuhlale kunamakhefu, izingcindezi nokwelula okwenza imifantu ephezulu ibonakale.
Amandla we-Glacial
Inguzunga yeqhwa iyahamba futhi isiphule amatshe ayizilinganiso ezisendleleni yawo. Izingcezu zamatshe ezibangelwa yilokhu kuhamba kwezinguzunga zeqhwa zaziwa ngokuthi ama-moraines. Indawo esekupheleni kweqhwa kulapho incibilikisi yakhiwa khona. Lapha, ungabona ukwakheka kwamagquma amancane abizwa nge-terminal moraine.
Inqobo nje uma i-glacier igcina indawo yokuqongelela engxenyeni engenhla yeqhwa kusukela emvuleni, umjikelezo weqhwa uzohlala uphila. Ekugcineni, endaweni engezansi, izinguzunga zeqhwa ziyancibilika, zakhe imifudlana emincane yamanzi amasha.
Kukhona izinguzunga zeqhwa ezigeleza ezigodini phansi kohlelo lwezintaba. Lapho zihlangana zakha i-glacier enkulu yaziwa njenge-piedmont.
Ama-polar caps kanye ne-ice cap
Lapho sesiqonda ukuthi iyini inguzunga yeqhwa, ukuthi yakha kanjani nokuthi iyini ngamandla ayo, siqhubeka nokuchaza izigaxa zeqhwa elisendaweni emincane. Uma i-glacier eshiwo ngenhla ihlanganisa amathafa wangempela neziqhingi ezisezingeni eliphakeme neliphansi, yaziwa ngokuthi i-polar cap. Lezi zindwani ezisezindaweni ezibandayo zivame ukuzalwa ezinguzini zeqhwa ezisezintabeni bese zehlela ezigodini. Ekugcineni, bafinyelela olwandle ngezikhathi ezithile.
Uma inguzunga yeqhwa inkulu kangangokuba imboza ubuso bezwekazi lonke, ibizwa ngokuthi i-ice sheet yezwekazi. Lokhu kwenzeka ngamakhemikhali eqhwa asezindaweni ezisemaphandleni e-Arctic nase-Antarctica. Lolu ungqimba olukhulu lweqhwa lugelezela ngaphandle luze lufinyelele olwandle futhi yilapho luqhekeka lube ngosayizi abahlukene lakha ama-icebergs.
Igama elithi polar caps lisetshenziselwa ukuchaza izinhlobonhlobo zeqhwa ezitholakala e-Antarctica naseGreenland. Ngakho-ke, noma nini lapho sikhuluma ngokufudumala komhlaba noma ngokushintsha kwesimo sezulu sikhuluma ngokuncibilika kwamakhekheba eqhwa asezindaweni ezibandayo. Lezi zinhlayiya ezisezindaweni eziphakeme kuzo zombili izingongolo zakhiwa ngesikhathi seqhwa lasePleistocene, esikhathini seQuaternary futhi zafika zamboza ingxenye enkulu yesifunda esisenyakatho.
Isigqoko se-polar saziwa njengesembatho seqhwa futhi imvamisa sinokwandiswa kwe- ngaphezu kwamakhilomitha-skwele ayizigidi eziyi-1,8 ebusweni. Ngokuya ngobukhulu, zikumamitha ayi-2.700 ubuningi. Lezi zindwangu ezisemaphandleni zimboza ingxenye enkulu yobuso baseGreenland. Idwala lesisekelo livela kuphela eduze nogu lapho inguzunga yeqhwa ingenamandla ngokwanele futhi izingcezu zakhe izilimi zeqhwa. Lapho izilimi zifinyelela olwandle, ziqhekeka ziqhubeke zibe izingcezu zeqhwa phakathi nenkathi yokuncibilika, zakhe izinguzunga zeqhwa.
Ama-Icebergs anamandla awo futhi ayanyamalala ngokuhamba kweminyaka. Isembozo se-polar salokhu okunamandla simboza i-Antarctica, kuphela lesi siqhwa inendawo engamakhilomitha-skwele ayizigidi eziyi-13.
Yini ebingenzeka uma izingqimba zeqhwa lasezindaweni eziphakeme zincibilika?
Ngokuguquka kwesimo sezulu nokwanda komphumela wokushisa okushisayo, kukhulunywa ngokuncibilika kwamakhekheba eqhwa asezindaweni ezibandayo. Umphumela walokhu ukuthi ulwandle luzonyuka. Cabanga ukuthi izingqimba zeqhwa zigxila cishe ku-70% wawo wonke amanzi ahlanzekile emhlabeni. Uma la manzi, lokho okusemhlabeni kugcina kuncibilikile, kuzophelela olwandle.
Ososayensi balinganisela ukuthi ngonyaka ka-2100, ulwandle luzobe selukhuphuke ngesilinganiso samasentimitha angama-50 ukusuka olwandle. Lokhu kusho ukuthi amadolobha amaningi asogwini azothinteka kabi futhi ezinye izinhlelo eziningi zemvelo kuzodingeka zivumelane futhi. Ngaphezu kwalokho, i- i-albedo yomhlaba izophinde ithinteke ngoba kunendawo encane emhlophe ekhombisa izehlakalo zemisebe yelanga.
Ngiyethemba ukuthi ngalolu lwazi ungafunda kabanzi ngamakhanda we-polar nemiphumela yokuncibilika kwawo.