Ƙasa ita ce cakudewar organic matter, ma'adinai, gas, liquid, da organism wadanda suka hadu domin taimakawa wa rayuwa. Bangaren ƙasa ta Earth, da ake kira da pedosphere, Nada muhimman ayyuka hudu na amfanin ƙasa: amatsayin hanyar dake taimaka ma tsirrai girma amatsayin abunda ke ajiye ruwa, samar dashi da tace shi amatsayin abunda ke sauya Earth's atmosphere amatsayin wurin da halittu ke rayuwa Dukkanin ayyukan nan, a zuwansu, suna sauya ƙasa.