Upper Mesa Falls plunges 114 feet over a 300 foot wide cliff face along Henrys Fork (also known as North Fork, a tributary of the Snake River) in Caribou-Targhee National Forest in southeastern Idaho, USA. Turn off Highway 47 on the Mesa Falls Scenic Byway about 15 miles north of the city of Ashton. On sunny days from about 9 am until 1 pm the mist from powerful Upper Mesa Falls creates a beautiful rainbow. The falls flow over Mesa Falls Tuff, which formed 1.3 million years ago. A cycle of rhyolitic volcanism from the Henrys Fork caldera depositing a thick layer of rock and ash which compressed and hardened over time. Between 200,000 and 600,000 years ago, the river eroded a wide canyon which was subsequently partly filled with basalt lava flows. The Henrys Fork of the Snake River carved a channel through the basalt to create today’s inner canyon.
Lower Mesa Falls plunges 65 feet along Henrys Fork, as seen from a separate viewpoint not far from the Upper Falls.