What evidence suggests that moai carving stopped suddenly at Rano Raraku?

Evidence suggesting that moai carving at the Rano Raraku volcano stopped suddenly is found in the state of the site itself. Both inside and outside the crater bowl, numerous unfinished statues remain, accompanied by thousands of crude stone picks scattered about the area.1

These abandoned tools and partially completed images indicate that the sculptors' work was interrupted abruptly. The unfinished statues reveal that the process involved polishing the front and sides of a figure before detaching its back from the bedrock; the presence of these figures in various stages of this process, left in the rubble below the quarries, serves as physical testimony to the sudden cessation of the work.1