Volcan Rano Raraku was used as a quarry for 500 years until the 18th century. The moai would be carved out of "tuff" (volcanic ash) here and then moved to their final location where they would be raised into place on their ahu (platform). Only then would the eyes (coral for the whites of the eyes and red scoria for the irises) be placed in the sockets. These moai were carved but never moved due to civil strife. The hundreds (almost 400) of moai look buried alive to me, with many actually inside the crater.