The Powder River Basin in Wyoming and Montana contains some 800 billion tons of brown coal, and the Lewis and Clark Expedition (1804 to 1806) reported fires there. Fires have been a natural occurrence in this area for about three million years and have shaped the landscape. For example, an area about 4,000 square kilometers in size is covered with coal clinker, some of it in Theodore Roosevelt National Park, where there is a spectacular view of fiery red coal clinker from Scoria Point.