But as the drainage basin that fed water to the troughs shrank, water flow ceased, and the fascinating formation -- with steps and risers cut high into the steep sandstone walls -- has been ...

so it would be difficult for the wind to carry the small rocks, which range in size from a quarter to a softball, said Jon Pelletier, a geoscientist at the University of Arizona in Tucson.

Some feel almost otherworldly, with strange rock formations and the occasional glow ... the limestone passages beneath southern Arizona hold some of the region's best-preserved cave formations.

“There’s a hill with a V-shaped collapse structure (the nose), two craters (the eyes), and a circular fracture pattern (the head),” The University of Arizona noted in a statement.

My colleague noticed something strange in the latest batch ... of Earth and Space Exploration at Arizona State University, wrote back to me: Balancing rocks (sometimes called Precariously Balanced ...