The moai are four meters high, on average, with larger examples reaching around 10 meters.  The exact form and style vary; the moai changed slowly over the history of their production, though most share general features, specifically elongated noses and ears.  They were carved originally from basalt, but this shifted in later years to the volcanic tuff found at the Rano Raraku quarry.  In either case, these statues were incredibly large and heavy -- the largest weighed around 86 tonnes -- and a lot of debate still exists as to how they were moved to their final positions.  Were they rolled on logs or “walked” upright using ropes and counterweights?  Once they were brought to their destination and mounted upright, white coral was used to fashion their eyes, and in many cases, a large red slag cylinder was placed on top of their heads, its size thought to be an indicator of tribal hierarchy or social importance.

The energy and resources that went into carving, transporting, and erecting the moai was significant, and is thought to be a key element of the societal decline of Rapa Nui in the 1800s.  As the population of the island increased, conflict among clans became heated, accelerating competition for resources.  Timber especially, a resource believed to have been critical in the transport and installation of the moai, became limited, and deforestation, resource depletion, and overpopulation collectively led to the near-collapse of Rapa Nui civilization.  As the conflict among clans ramped up, they began actively knocking down or defacing one another’s moai.  When Captain Cook arrived in 1774, a few of the statues had been knocked down, but most remained upright; by the mid-1800s, only a few moai remained standing.  This period in Rapa Nui history is covered thoroughly as a chapter of the book Collapse: How Societies Choose to Fail or Succeed by Jared Diamond, and is a fascinating read.