Information taken from South Central Idaho and other local brochures.
The Hagerman Valley was formed 15,000 years ago by the Bonneville flood which gouged out canyons, moved house-sized boulders and left enormous sand bars. The Valley's landscape is dotted with uncounted numbers of “rock melons” giving silent testimony to the colossal flood which originated in the Bonneville Lake area, nearly the entire western part of Utah. The Valley is a land of water, with hot and cold springs, volcanic lava flows, deep box canyons, fossil beds, mine diggings and vast rock formations. It is a land of hot summers and mild winters; a land that has served Native Americans, emigrants, settlers, farmers and ranchers for hundreds of years.
The heart of the Valley is the Snake River Canyon. For fishermen, water skiers, boaters, bird watchers and white water enthusiasts, the Snake is one of the premier rivers of the West. It has high, palisade walls which are a majestic sight.
Unique to the Valley are the natural springs that gush from the lava canyon walls and percolate up from underground sources from the great Snake River Aquifer. They provide not only spectacular scenic beauty, but also pure, clear oxygenated water at a constant temperature of 58 degrees, the ideal temperature for raising trout. Local business, Clear Springs Foods, is the largest producer of trout in the world. Approximately 70A% of all the trout produced in the US. Come from all the local fisheries within a 30 mile stretch along the Snake River in the Valley.
Me speaking, now.
The north side of the river is the plateau. On top is fairly flat, fertile farm and ranch land punctuated with gorges which must have surprised passing emigrants as they suddenly came upon them. Just under the surface of the northern plateau is lava flow. The gorges are primarily basaltic columns and basalt pillows. You'll see photos of those in the entry about Malad Gorge.
The south side of the river is hardened sandy rocks left by the passing Bonneville Flood waters and later by the Missoula Flood waters. On the top of south of the river land are located those bean farms, dairy farms and “wind” farms with their huge turbines seen for miles around. Just under the surface is the Hagerman Fossil Beds.