Pyramid PitsSeldom does nature willfully sculpt such symmetric, angular forms, especially on scales larger than mineral crystals. In two dimensions, this strangely straight-sided puddle looks like a cartoon drawing of two mountain peaks. Actually it was a pit in igneous, beachfront bedrock, composed of two inverted, triangular and partially superimposed pyramids. Three kinds of water action helped to dig this hole from pre-existing fractures in very hard, very old (Precambrian) bedrock: glacial scouring thousands of years ago, freeze-thaw processes to break open cracks ever since, and direct pounding from Lake Superior's waves to hose out sedimentary debris and maintain smoothness.
1 W Michipicoten River Village, ON, Canada (15 Jul 7) , looking down