Snake River: Hells Canyon Depth, Shoshone Falls & Lower Snake Dam Ecology

## The Volcanic Canyon Highway of the Intermountain West

Originating at 9,500 feet elevation on the Two Ocean Plateau in Yellowstone National Park, Wyoming, the **Snake River** arcs **1,078 miles (1,735 kilometers)** across southern Idaho before cutting north along the Oregon-Idaho border and joining the Columbia River at Pasco, Washington.

### Hells Canyon: America\'s Deepest River Gorge
While the Grand Canyon is celebrated for its width and colorful layered strata, **Hells Canyon** on the Snake River is the deepest river gorge in North America:
- **Maximum Depth:** 7,993 feet (2,436 meters) from the summit of He Devil Peak in the Seven Devils Mountains down to the river surface.
- **Geological Composition:** Formed by the river carving through exotic accreted oceanic island-arc volcanic terranes uplifted alongside Columbia River flood basalt eruptions.

### Shoshone Falls & Salmon Migration Barriers
At Twin Falls, Idaho, the river plunges 212 feet (65 meters) over **Shoshone Falls**—a precipice 45 feet higher than Niagara Falls. For millenia, this massive cataract formed an impassable natural barrier, preventing Pacific salmon from reaching the upper 600 miles of the Snake River.

### The Four Lower Snake River Dams
Between Lewiston, Idaho, and the Columbia confluence, the federal government maintains four multi-purpose run-of-the-river dams: **Ice Harbor, Lower Monumental, Little Goose, and Lower Granite**. Environmental organizations, tribal nations, and fishery biologists advocate for breaching these dams to restore plummeting endangered chinook and sockeye salmon runs.

*Data Source: USGS Idaho Water Science Center & US Fish and Wildlife Service Pacific Region.*