What were some of the issues that split the eastern and the western churches?

The division of the church between East and West was casued for different reasons:

Discrepancies regarding language: Greek was the language spoke and written by Eastern Church, whereas Latin was the language used by the West.Pepin donation of land in central Italy to the papacy in 756: by donating this land, he made the pope focus more in the West and basically overlook the East. Also, Charlemagne, who was Pepin's son, came to Rome and on Christmas Day, 800, Pope Leo III crowned him Holy Roman Emperor.  This act was the symbol of the division between East and West.The filioque controversy: There were discrepancies regarding to the question of who sent the Holy Spirit: if it was the Father or the Father and Son. The issue over the dating of Easter: In the beginnings of the church, Easter was celebrated on Passover in the East, whereas Easter was always celebrated on a Sunday in the West. The Great Schism: This was the final break and it took place on 16 June 1054. Michael Cerularius was expelled by Pope Leo IX because he tried to degrade and destroy the holy catholic and apostolic church. Pope Leo was afterwards expelled by The Patriarch.

He gathered information from primary sources.