Desert Hill or Ridge Formed by the Wind
Puzzle 3 of Famous Horses Hard Pack
Question is: Desert Hill or Ridge Formed by the Wind
and the answer is: SANDDUNE
Word Meaning:
SAND DUNE — (geology) A large, semipermanent mound of windblown sand, held together by specialized plants, common along seashores and in deserts.
Definitions from Wiktionary.