Region 3: The Rocky Mountains

The high topography of the Rocky Mountains provides context both for hydroelectric power and wind energy. The same rugged peaks and valleys that contribute to localized high winds also make large-scale wind energy development difficult. The Rocky Mountains region is also known for coal, oil, and gas, in this case from large freshwater sedimentary deposits in the Greater Green River Basin.

Oil and Gas

Petroleum resources are extracted in the Greater Green River Basin (see Figure 7.5). The Greater Green River Basin is itself made up of several smaller basins and arches between them, formed during the Laramide Orogeny from the end of the Cretaceous period into the Eocene. The basin is known for its Eocene-aged surface rocks that contain both mineral and fossil fuel resources, along with its unusually well-preserved terrestrial fossils in the Green River Formation. Fossil fuels, thought to be derived from blue-green algae living in ancient lakes, are found in particularly thick sequences of Eocene oil shale. The Green River Formation hosts the largest known oil shale deposits in the world.

The Greater Green River Basin also contains other fossil fuel resources of lesser renown. For example, the largest of the arches in the basin, the Rock Springs Uplift (which divides the basin into the Green River Basin on the west and smaller basins in the east) contains coal deposits that were first mined as fuel for the Union Pacific Railroad during the building of the Transcontinental Railroad and subsequent railroad operations. Conventional oil and gas drilling has also occurred in the basin, in Cretaceous-aged deltaic rocks from the Western Interior Seaway (Figure 7.12). The Wamsutter gas field, occupying a 89-kilometer-long (55-mile-long) portion of Wyoming’s Red Desert, has recently experienced an energy boom, with more than 2000 gas wells projected to be operational there by 2020.

Figure 7.12: Natural gas drilling rigs in the Upper Green River Valley.

Hydroelectric Power

Since the Rocky Mountains provide an abundance of water to lower regions in the east and west, hydroelectric power is substantial in this area (Figure 7.13). The Clark Fork and Kootenai Rivers (tributaries of the Columbia River that flow through Montana and Idaho) are major rivers that provide the potential for much of the Rocky Mountains’ hydropower, which uses the gravitational force of falling or rushing water to rotate turbines that convert the water’s force into energy. The three largest hydropower plants in Montana—Noxon Rapids Dam (580.5 MW), Libby Dam (525 MW), and Hungry Horse Dam (428 MW)—are located along these rivers and their tributaries, helping to make Montana one of the largest producers of hydropower in the US (Figure 7.14).

Figure 7.13: Hydroelectric plants in the Northwest Central.

Figure 7.14: Libby Dam, on the Kootenai River in Lincoln County, Montana. This dam is 129 meters (422 feet) tall and 931 meters (3055 feet) long, with a generating capacity of up to 600 megawatts.

Wind Power

The Rocky Mountains region has some of the highest potential for wind energy in the US (see Figure 7.11), though the area’s terrain and lack of infrastructure can make tapping into this resource challenging. Windmills along I-80 in southeast Wyoming near Medicine Bow, where a gap exists in the Rockies, were among the first large-scale wind farms in the US. These facilitated high voltage transmission lines along the Interstate. There are a number of locations in southwestern Montana and northwestern Wyoming where valleys are oriented such that winds are funneled relatively consistently through the year; these areas have future potential for expanded wind farms.