Simplify the following text for a Grade 8 native English-speaking person.
Original: This is partly because of the disproportionate size of most moai heads and partly because , from the invention of photography until the 1950s , the only moai standing on the island were the statues on the slopes of Rano Raraku , many of which are buried to their shoulders .
Simplified: Most were made from the volcanic rock in the Rano Raraku area of the island . Moai are sometimes called `` heads '' but they do have shoulders , arms , and a body but these are usually too small for the head , also some of the best known ones had been partly buried over the years and only the heads were showing .