Final answer:
The event that marked the split between the Roman Catholic pope and the eastern patriarch was the Great Schism of 1054. This schism was caused by differences in language, ecclesiastical practices, and conflicting views on clerical authority. It resulted in the formation of the Eastern Orthodox Church and the continuation of the Roman Catholic Church.
Step-by-step explanation:
The event that marked the split between the Roman Catholic pope and the eastern patriarch was the Great Schism of 1054. This division was the result of burgeoning differences in language, culture, and ecclesiastical practices between the western church, which used Latin and had a celibate clergy under the supreme authority of the pope, and the eastern church, which practiced in Greek, permitted married priests, and considered the patriarch as one of the several equivalents in authority. During a pivotal moment in 1054, tension culminated when the pope's emissaries excommunicated the Patriarch of Constantinople, who in turn excommunicated the pope's representatives, hence solidifying the schism and leading to the formation of the Eastern Orthodox Church and the continuation of the Roman Catholic Church.
Over time, this split became more entrenched, with the Roman Catholic Church experiencing further fragmentation during the Protestant Reformation and the Eastern Orthodox Church spreading its influence into Eastern Europe and Russia. The theological and organizational differences that separated these branches of Christianity after the Great Schism have persisted throughout history, shaping the landscape of Christian practice in various parts of the world.