Thanks, but.....
These things are found at an altitude of over 5,000 ft and are perfectly---emphasis on perfectly-round between 5 and 6ft in diameter. Uniform erosion, repeated over and over doesn't seem to be an adequate explanation.
However, thanks for trying---now if you have a neocon explanation for Cheney sending in his required $ 7.00 license fee two days after he shot his lawyer, THAT might be interesting.
Publius