Umchazamphansi uyigatsha lenzululwazi yemvelo elinake uMhlaba nezinye izindikimba zomkhathi, amatshe ezakhiwe ngawo, nezinqubo eziguqula ukuma kwazo ngokuhamba kwesikhathi. Leli gama elithi umchazamphansi liyinhlanganisela yamagama amabili 'umchaza + umphansi", elithi umphansi lisho umhlaba, ukusho ukuthi umchazamhlaba ohlozinga amatshe namdwala owakhiwe ngawo ngaphansi. Umchazamphansi wanamuhla uhlanganisa zonke ezinye Izunzululwazi zomhlaba, kufaka phakathi nomchazayila (hydrology). Uyadidiyelwa nalapho kufundiswa Inzululwazi yesomiso soMhlaba nenzululwazi yemizulane.

Umchazamphansi uchaza Ukwakheka Komhlaba ngaphezulu nangaphansi kobuso bawo kanye nezinqubo ezakha leso sakhiwo.