I'm sorry, I shouldn't have posted that without checking out your page on the image first. Doh! Right there in little italic letters:

Robert Shepherd suggests this:



How about a really unusual optical illusion, that can be something entirely different if you look at it differently?

Try this one: It's a long slope cutting through many layers of thin rock. This rock fractures into rectangular blocks, and where it's exposed it looks like a pile of mah-jong tiles. The left and bottom edges of the rock are shadowed. The left edge forms what people are interpeting as a geyser or dust devil, lifting up from what seems like a horizontal streak on the ground, but's really the bottom edge.

The effect's not clear near the top of the image, but as you get near the bottom the "tiles" are larger and better-defined. Your small version also shows the effect better than the original-size, I think because the original has some blurriness that heightens the illusion of dust or gas.

...
BTW, a side effect of shifting to this perception is that you can now see a neat little "anomaly": Near the top of your sepia image, center, one of the blocks has a smaller block on top, and two look a lot like a building with an air-conditioning unit on top. he he he...

--Robert



Oh man...not the first time I've repeated myself unnecessarily. Even mimicked the same tone of revealing some great mystery. Sorry about that. Doh!

--Robert in realtime