"It is likely that they were moved by hand, but tree logs could also have been used."
Dr. Sue Hamilton, of University College, London, said: "The hat quarry is inside the crater of an ancient volcano and on its outer lip. A third of the crater has been quarried away by hat production."
"So far we have located more than 70 hats at the ceremonial platforms and in transit. Many more may have been broken up and incorporated into the platforms."
Richards said there was evidence the quarry, known locally as Puna Pau, had previously produced statues before changing to hats.
"Initially the Polynesians built the moai out of various types of local stone, including the Puna Pau scoria, but between 12,000 to 13,000 B.C., Puna Pau switched from producing statues to hats.
"The change correlated with an increase in the overall size of the statues across the island."