Paleontology and geology
The most prominent Quaternary feature in Idaho is the Snake River Plain, the broadly U-shaped, relatively flat area near the southern boundary of the state. This area consists of lava flows, some quite young, and fossiliferous lake and river deposits. Other Quaternary-age deposits include glacial valley sediments, layers of wind-blown glacial dust (loess), and scattered basalt flows outside the Snake River Plain. Two hundred species of vertebrates are known from the Quaternary of Idaho. The most common are mammoths, horses, camels, bison, mountain sheep, ground sloths, rodents, rabbits, birds, snakes, lizards, and fish. The rich mammoth site of Tolo Lake in western Idaho near the Washington/Oregon border is Quaternary in age. Mollusc fossils are also common in some areas.