The Giant Ripples of Camas Prairie

Ahead of you some 3,000 feet in the distance are a series of prominent ridges that are just a few of the hundreds of Giant Ripples of Camas Prairie. The ripples, some of which are thousands of feet long and up to 45 feet high, were created 15,000 years ago when the last ice age neared its end in North America. Interestingly, in this exact spot close to that time, you would be standing beneath a thousand feet of frigid water of Glacial Lake Missoula, formed when an enormous lobe of glacial ice blocked the Clark Fork River in northern Idaho. The lake that formed behind the ice dam expanded until it was about half the size of Lake Ontario. The ice dam eventually collapsed and Glacial Lake Missoula emptied catastrophically to the west, its waters roaring to the Pacific Ocean. The Camas Prairie ripples were formed by the currents associated with the colossal emptying of Glacial Lake Missoula, which unleashed nearly 650 times the amount of energy released by the Mount St. Helens eruption of 1980. What sets the giant ripples apart from other similar geologic features is that they are the largest ripples on Earth. In fact, most ripples that are formed by rivers today are only inches high, and they are mostly made up of sand-sized particles. Many of the Camas Prairie ripples are composed of boulder-sized geologic debris, and since the size of ripples is related to the strength of a river’s currents, the ripples we see here were created by currents so powerful they are difficult to comprehend in light of today’s natural events. Fortunately for us, the giant ripples have been preserved as silent monuments of Montana’s prehistoric and chaotic past.