Photo of volcaniclastic units of the Absaroka volcanic province in northeastern Yellowstone National Park

Photo of geologic units of the Absaroka volcanic province in northeastern Yellowstone National Park that shows volcaniclastic sandstones grading up into a conglomerate, followed by another sequence of sandstone to conglomerate. These repeating layers of the same-looking material make it difficult to assign them to a specific volcanic group. Photo by Natali Kragh, Montana State University, July 9, 2020.