A Geometric Puzzle

I finally decided to take a day off from working around the house and head out for a rare (lately) day shooting some new work. Joshua Tree N.P. is now only 80 miles or so from home (and the most photogenic location in my area), so we drove out there for a quick day trip.
This formation known as the Giant Marbles, is one of the most interesting among so many to be found here.. I had never managed to locate it on previous trips, but it was quite easy to find with some quick directions from a ranger at the visitor center. Molten magma that rose up under the earth eons ago, solidified, cracked and was then exposed when the softer soil eroded away, explains the geometric stacking effect. The soft light on the rocks is just a minute or so before the sun set behind a ridge, casting the whole scene into shadow and killing the color... glad I got the composition I wanted just at the right moment. For a sense of scale, the round "marble" balancing on the top is probably 5-6 ft. diameter.