What on Earth? Optical Illusion

My 9 year old son looked at this image and quickly deduced what the mystery was about the strange image he was seeing. Me, well let's just say it took me a while longer to arrive at the same conclusion he did.

So "What on Earth" do you see in this picture?

Photo by Robert Chura
Copyright 2002
used w/permission

He is a talented photographer check out his work here.

Still not sure what this is? Place your mouse on the photo to see the truth.

For more information on this effect check out this post Bumps or Holes? Astronomy Analysts Confused