During the Pliocene Epoch, three to four million years ago, Idaho was warmer and more humid, with annual rainfall of 20 inches. Ancient pollen in sand and clay layers suggests trees and grasslands supported many creatures, including mastadons, camels, and horses alongside smaller animals such as shrews, turtles, and fish. More than 200 species of plants and animals have been excavated from the cliffs, where bones and pollen were left in the sediment. Study of these fossils indicates that the climate later became cold and dry as the first ice age arrived. Some animals adapted, some migrated, and others became extinct. Hagerman preserves one of the world’s most prolific accumulations of fossils from the Pliocene Epoch, revealing the consequences of a changing climate.

Photo: Barry Swackhamer

Hagerman, Idaho · USA