Columbia River Basalt Group
eastbound on Interstate 90
- Montana (Wikipedia)
Montana (/mɒnˈtænə/) is a state in the Mountain division of the Western United States. It is bordered by Idaho to the west; North Dakota and South Dakota to the east; Wyoming to the south; and by the Canadian provinces of Alberta, British Columbia, and Saskatchewan to the north. It is the fourth-largest state by area, the eighth-least populous state, and the third-least densely populated state. Its state capital is Helena. The western half of Montana contains numerous mountain ranges, while the eastern half is characterized by western prairie terrain and badlands, with smaller mountain ranges found throughout the state. In all, 77 named ranges are part of the Rocky Mountains.
Columbia River Basalt Group map shows main regions of basalt exposure in Washington, Oregon, Idaho and Nevada, USA. (usgs.gov)