Dig down and you will find the bedrock again, and dried-out clay. That's not to say the areas can't be interesting. Roaming sand dunes can preserve what they bury, including some astonishing ...

MOSCA, CO - JUNE 20: Hikers Tara Eisenhour, in front, and Jim Smith, in back, make their way towards the top of the dunes at the Great Sand Dunes on June 20, 2019 in Mosca, Colorado.