We're still in Jumbo Rocks. These rocks erode into some wonderful, and sometimes baffling, shapes. Here it seems the tree is holding the round rock in place. The rock is just balanced there, I can easily crawl under it and out the other side. Is the tree therefore as old as the shape of the rock? It would seem so. As the rock eroded into a ball it would certainly have rolled away a long time ago (perhaps during the Landers earthquake, for example).