       National Monument CO,UT  The Ancient Desert  Q. How do we
know this was a desert?  A. We can tell that much of this
sandstone is made up of dune deposits because it displays
enormous cross-bedding. Cross-bedding is the set of swooping
lines you can see as you look at an outcrop, and represents the
steep sides of the dunes, preserved as the wind drove the dunes
across the desert. The constant flow of any kind of fluid can
form cross-beds, but ones this size can only be formed by wind.
Sand Dune Drawing of how wind blows sand across the backside of
a dune and then deposits grains on the steep face of the dune to
keep the dune migrating in the desert. National Park Service
Real Sand Dune  Cross-bedding found in the Glen Canyon Formation
at Dinosaur National Monument.  National Park Service  As you
explore Dinosaur National Monument, keep an eye out for cross-
bedded rocks. You might find that they're more common than you
think!  Desert Lakes  National Park Service  Q. Where did the
animals and plants that