lasted from about . The eroded remnants of many large stratovolcanoes are found in the area. The dissection of these long extinct volcanoes by erosion allows geologists to see volcanic structures that are impossible to see in active volcanoes. Many terms now widely used in volcanology originated in nineteenth century field studies of these ancient volcanoes. Gallery See also List of mountains and mountain ranges of Yellowstone National Park List of mountain ranges in Montana List of mountain ranges in Wyoming References External links Ranges of the Rocky Mountains Mountain ranges of Wyoming Mountain ranges of Montana Greater Yellowstone Ecosystem Landforms of Park County, Montana