The lower falls are 308 feet (94 m) high, or almost twice as high as Niagara. The volume of water is in no way comparable to Niagara as the width of the Yellowstone River before it goes over the lower falls is 70 feet (22 m), whereas Niagara is a half mile (800 m).
The lower falls descend from the 590,000 year old Canyon Rhyolite lava flow. The lower falls of the Yellowstone is still the largest volume major waterfall in the Rocky Mountains of the United States. The volume of water flowing over the falls can vary from 63,500 USgal/s (240 m³/s) at peak runoff to 5,000 USgal/s (19 m³/s) in the fall.