Grand Canyon of the Yellowstone

A view over the Grand Canyon of the Yellowstone, Wyoming, US, showing the Lower Falls. There are various viewpoints along the rim, giving dizzying views down into the canyon. It's a long way down! Taken on 14 September 2012 - lots of haze from several forest fires that were burning within the park. (As usual, locations marked on my maps are very approximate, more to remind myself roughly where an image was taken.)

"The Grand Canyon of the Yellowstone River slices through an ancient hydrothermal basin. The basin developed in rhyolitic lava and ash that flowed into the Yellowstone Caldera about 500,000 years ago. The river carved this spectacular canyon through the hardened lava (rhyolitic rock) and welded ash (tuff). Hot areas and steam vents still exist in the canyon. They allow heat, gases and hot water to escape from the underground Yellowstone Volcano. The canyon is about 20 miles (32 kms) long and parts of the canyon are nearly 1,200 feet (366 m) deep." Taken from a sign at the Canyon.