But Baldy is a “blowout”: a victim of ... that sections of clay undergirding the dune had eroded, allowing groundwater to pipe away columns of sand. Locals reminded Argyilan that there had ...

Star dunes - sometimes called pyramid dunes - stand out among sand dunes for their towering height and eye-catching form.

This story appears in the November 2012 issue of National Geographic magazine. I got my first lesson in the physics of sand dunes in 1998 on an expedition into the Sahara. In order to take aerial ...