climate
Glaciers have been an important feature of the earth's landscape during the present Cenozoic era, which spans about 65 to 70 million years. Cooling near the end of the era began in the Pliocene epoch, and mountain glaciation in the western United States occurred somewhere between 1 and 2 million years ago. [Source: Encyclopedia of Time: Science, Philosophy, Theology, & Culture; Glaciers]
glaciers
concepts