I-glaciation inqubo yokwakheka komhlaba eyenzeka lapho iqhwa elikhulu, ebizwa ngokuthi izinguzunga zeqhwa, ukwakha emhlabeni noma ukuhamba ngaphesheya kobuso boMhlaba. Izinguzunga zeqhwa zakhiwa ngeqhwa eliye lanqwabelana eminyakeni eminingi, okugcina kucindezelwe bese kwakheka iqhwa. Iqhwa lenzeka ezindaweni lapho izinga lokushisa lihlala lingaphansi kwezingaqhwa futhi lapho kuneqhwa elanele lokusekela ukwakheka kwezinguzunga zeqhwa..
Kunezinhlobo ezimbili eziyinhloko zamaqhwa: ama-glaciers esigodini namashidi eqhwa. Izinguzunga zeqhwa zinde, izinguzunga zeqhwa eziwumngcingo ezigeleza ezigodini futhi zingatholakala ezindaweni ezinezintaba. Amashidi eqhwa, Ngokolunye uhlangothi, zinkulu kakhulu futhi zithatha izindawo ezinkulu zomhlaba, njengeqhwa laseGreenland nelase-Antarctic.
Izinguzunga zeqhwa zinomthelela omkhulu endaweni yoMhlaba futhi zingaguguleka, ezokuthutha, futhi bafake izinsalela eziningi lapho behamba. Njengoba izinguzunga zeqhwa zihamba ezweni lonke, bangabaza izigodi, dala ama-ridges nama-moraines, futhi ulolonge isimo sendawo yonke sezwe.
I-glaciation ingaba nomthelela omkhulu esimweni sezulu soMhlaba, njengoba izinguzunga zeqhwa zikhombisa ukukhanya kwelanga okuningi emuva emkhathini kunomhlaba noma amanzi, okubangela ukupholisa isimo sezulu. Phakathi nenkathi yokugcina yeqhwa, okwenzeka cishe 2.6 million ukuze 11,700 iminyaka edlule, izingxenye ezinkulu zomhlaba zazimbozwe amaqhwa namaqhwa, okuholela ekushintsheni okukhulu kwesimo sezulu soMhlaba kanye nemvelo.
Namhlanje, izinguzunga zeqhwa ziyizinkomba ezibalulekile zokushintsha kwesimo sezulu, njengoba ubukhulu bawo kanye nezinga lawo kuhlobene eduze namazinga okushisa omhlaba. Ukuhlehla kwezinguzunga zeqhwa, njengoba kubonakala ezingxenyeni eziningi zomhlaba omkhulu, kuwuphawu lokufudumala kwembulunga yonke futhi kunomthelela omkhulu ekukhuphukeni kwezinga lolwandle, imithombo yamanzi, kanye nezinhlelo zemvelo.