Blessings and Cursings

Immediately after their victory at Ai, Joshua gathers the Israelites together to worship the Lord and renew the covenant at Shechem. Following the commands of Moses in Deut. half of the tribes stand on Ebal while the other half stand on Gerizim with the Ark and the Levites between them. The Blessings and Cursings of the covenant are then pronounced and the Word of God is read. What was the purpose of this worship service, what did this great ceremony point to, and what is its importance to us?