This valley (west of Cody, Wyoming) shows evidence that it was shaped by a glacier or glaciers. The valley is "u" shaped which indicates that the walls and floor of the valley were scraped and pushed into this shape by a huge glacial river of ice and rock. As the glaciers pushed down the valley, their weight and motion carved this valley into the shape you see here. When the glacier retreated, it left a moraine of pulverized rock and soil. There have been five major ice ages in the history of the earth and this glacier could have been born in the current epoch: the Quaternary Ice Age. This latest ice age started about 2.5 million years ago and has lasted until now.