Complex sentence: The Columbia River Basalt Group (including the Steen and Picture Gorge basalts) is a large igneous province that lies across parts of the U.S. states of Washington, Oregon, Idaho, Nevada and California.
Split into simpler sentences: The Columbia River Basalt Group is a large igneous province that lies across parts of the Western United States. It is found in the U.S. states of Washington, Oregon, Idaho, Nevada, and California.