Hells Canyon

The geologic history of the rocks of Hells Canyon began 300 million years ago with an arc of volcanoes that emerged from the waters of the Pacific Ocean. Over millions of years, the volcanoes subsided and limestone built up on the underwater platforms. The basins between them were filled with sedimentary rock. Between 130 and 17 million years ago, the ocean plate carrying the volcanoes collided with and became part of the North American continent. A period of volcanic activity followed, and much of the area was covered with floods of basalt lava, which smoothed the topography into a high plateau. Area rivers began carving Hells Canyon out of the plateau about 6 million years ago. Water from Lake Idaho overtopped a natural divide between it and the Salmon River around 3 million years ago, allowing the Snake River to flow through the plateau and further carve the canyon. A 2025 study concludes that the canyon is younger than previously thought, beginning only 1.6 million years ago. Significant canyon-shaping events occurred as recently as 15,000 years ago during a massive outburst flood from Lake Bonneville in Utah. The canyon rim contains dense forests, scenic overlooks and mountain peaks. At the bottom of the canyon, the area is a dry, desert environment. ==History==

windingthrough Hells Canyon Inhabitants The earliest known residents in Hells Canyon were the Nez Percé tribe. Others tribes visiting the area were the Shoshone-Bannock, northern Paiute and Cayuse Indians. The mild winters and ample plant and wildlife attracted human habitation. Pictographs and petroglyphs on the walls of the canyon are a record of the Indian settlements. In 1806, three members of the Lewis and Clark Expedition entered the Hells Canyon region along the Salmon River. They turned back without seeing the deep parts of the canyon. It was not until 1811 that the Wilson Price Hunt expedition explored Hells Canyon while seeking a shortcut to the Columbia River. Hunger and cold forced them to turn back, as also did many explorers who were defeated by the canyon's inaccessibility. There remains no evidence in the canyon of their attempts; their expedition journals are the only documentation. Damming the Snake River After completion of large hydropower dams on the Columbia River in the 1930s through the 1950s, several entities sought approval from the Federal Power Commission to build dams on the Snake River, including a high dam in Hells Canyon. The three dams have a combined generating capacity of 1,167 megawatts (MW) of electricity. The complex, which provides about 70 percent of Idaho's hydroelectricity, blocks migration of salmon and other anadromous fish upstream of Hells Canyon Dam. Two additional dams, Mountain Sheep and Pleasant Valley, were proposed in 1955 above the mouth of the Salmon River and below the Hells Canyon Dam. The Wild and Scenic Rivers Act of 1968 held up progress, but with the energy crisis, they were revived in 1975; these projects were sponsored by consortiums Pacific Northwest Power Company and Washington Public Power Supply System (WPPSS). At the end of that year, President Gerald Ford signed legislation to create the Hells Canyon National Recreation Area and the projects The first river runners were on the canyon rapids by 1928. ==Recreation==

In 1975, Congress had declared to be the recreational area for the Hells Canyon National Forest. Activities in Hells Canyon include fishing, jet boat tours, hunting, hiking, camping, and whitewater sports (mainly rafting and kayaking). Much of these activities rely on the mighty Snake River, which is the main factor in the creation of Hells Canyon. The Snake River is home to numerous fish species, an abundance of class I-IV rapids (some of the largest in the Pacific Northwest), diverse wildlife and miles of systems. There is one boat ramp that is located at the upper end of the Snake River. The wildlife is made up of over 350 species and this includes big game, small game, bird, and waterfowl hunting. These key components make Hells Canyon an outdoor recreation mecca that brings in tourists from around the world. Hells Canyon offers tours year round, while most of the whitewater activities peak in summer months. To participate in these recreational activities one can utilize commercial charters or private trips. ==Access==

There are three roads that lead to the Snake River and they are located between Hells Canyon Dam and the Oregon-Washington state line. There are no roads that cross Hells Canyon. The road crosses the dam and continues another mile to the Hells Canyon Visitor Center on the Oregon side. Farther north on the Idaho side, Deer Creek Road connects White Bird to the river at Pittsburg Landing. Near the northern end of the canyon, Forest Road 4260 (Lower Imnaha Road), the last part of which is too rough for most cars, reaches the river at Dug Bar, from Imnaha, Oregon. On the canyon rims, viewpoints accessible by road include Hat Point and Buckhorn in Oregon and Heavens Gate in Idaho. ==See also==

• Orr, Elizabeth L., and Orr, William N. (1999). Geology of Oregon, fifth edition. Dubuque, Iowa: Kendall/Hunt Publishing Company. . • Sullivan, William L. (2002). ''Exploring Oregon's Wild Areas'', third edition. Seattle: The Mountaineers Press. . ==Further reading==