History Written on Trees

About 500 miles from its headwaters in Yellowstone National Park, the Yellowstone nears the end of its 670-mile journey to its confluence with the Missouri River. The last of America's free flowing rivers, it drains 70,100 square miles of land, an area the size of North Dakota. Floods are a natural part of the river ecosystem, carving out new habitats, maintaining biodiversity, and improving water quality. In this area, flooding can be seen at the bases of cottonwood trees where bark has been peeled away. These "ice scars" form when large ice jams break up and slam ice chunks into the trees. By studying a tree's growth rings and scarred surface, patterns of flooding events can be reconstructed; for example, scars here were formed during a flood in 1978 and can help determine soil movements over time.

Montana · United States