Canyon, Wyoming

Canyons don't form everywhere, only in places where a river is cutting downward much faster than the rocks it cuts are weathering. That creates a deep valley with steep, rocky sides. Here, the Yellowstone River is strongly erosive because it carries a lot of water at a steep gradient down from the high, uplifted plateau around the huge Yellowstone caldera. As it cuts its way downward, the sides of the canyon fall into it and are carried away.