Sloping slightly sideways on the grassy hills beneath the Ranu Raraku volcano, a giant stone head known as a moai shows the wear and tear of time on this triangular 64-square-mile island.

On the right side of the oblong rectangular face with male features, the rock is lighter in color and its long, carefully sculpted ear and nostril are clearly visible. But on the statue's left side, the sun and wind have eroded the nose, lip and ear.

"The moai are dying by natural causes," said archaeologist Sergio Rapu, a lifelong researcher of this isolated South Pacific island of hills and extinct volcanoes also known as Rapa Nui. "The prehistoric Rapa Nui people noted it would take 300 to 400 years for the statues to become completely eroded."