What caused the great schism

The primary cause of the great schism was due to disputes over the authority of the pope. The Roman Pope claimed he held authority over the four eastern patriarchs, while the four eastern patriarchs claimed that the primacy of the patriarch of Rome was only honorary, and thus had authority only over Western Christians.

Though normally dated to 1054, when Pope Leo IX and Patriarch Michael I excommunicated each other, the East - West Schism was really a result of an extended period of estrangement between the two bodies of Churches.