The Snake River and the Falls

The Snake River that runs through Idaho Falls is not the wild mountain torrent it becomes in Hells Canyon far downstream. Here on the Snake River Plain it moves broad and deliberate across a floor of black basalt, the product of volcanic eruptions stretching back two million years. The plain itself is the cooled remnant of lava flows from the Yellowstone hotspot as the North American plate has drifted slowly southwest over the geological hot zone. Every basalt ridge you see here, every lava tube and cinder cone, is a record of how close Yellowstone's fire came to this ground.

The falls the city is named for are not thunderous. They are more of a long rapid than a dramatic plunge. Long before the city grew here, this stretch of river was a gathering place for the Native peoples of the region.

The falls you see today are partly the work of engineers. In eighteen ninety-one town leaders renamed the town Idaho Falls for the rapids below the bridge. Some years later, a retaining wall built for a hydroelectric power plant transformed those rapids into waterfalls. The riverfront walkway beside them is the same Snake River, shaped by the same basalt.