Complex sentence: It is located directly adjacent to Interstate 5 at milepost 742 between the city of Mount Shasta and Weed, California, with the highway crossing a pass, Black Butte Summit, at the western base of the lava domes.
Split into simpler sentences: It is located directly adjacent to Interstate 5 at milepost 742 between the city of Mount Shasta and Weed, California. The highway crosses a pass, Black Butte Summit, at the western base of the lava domes.