Interesting find near an excavation site.

One of the visiting archaeologists noticed an interesting, rounded, smooth indentation in large boulder near an archaeological excavation site along one of the nature center trails.  (The site proved to be a hearth used by ancient peoples who used to live in the area, but that a post for another day.)  The official name of this type of indentation is a metate.  What do you think caused this indentation? (no fair peeking at Wikipedia!)

Archeologist noticing a curious indentation in a boulder. (Courtesy of Paula Richards)

Here’s a hint….  a stone similar to this one can often be found near metates.  Notice how rounded the edges are and how smooth the overall stone is.  This stone is known as a mano.

Mano stone
Sizing up a mano stone. (Courtesy of Paula Richards)

The next time you’re out at the nature center, be sure to look for the boulder near the site of the newly discovered ancient hearth.  Think about how long the ancient peoples would need to work the mano stone to make it and the metate as round and smooth as they are.

Answer found at this link.