The chief volcanoes in the St. Elias Range are Mount Bona and Mount Churchill. At and , respectively, they are the highest and fourth-highest volcanoes in the United States and the fourth and seventh highest in North America, and Bona is the tenth highest peak of any kind in North America. Churchill is often regarded as a subsidiary peak of Bona. Both are ice-covered stratovolcanoes. Churchill is the source of the White River Ash. It erupted about 100 AD and 700 AD, spreading ash across much of Alaska and northwestern Canada.