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St. Louis, Missouri
July 8, 2002
It is believed that many years ago, a rhyolite lava flow covered the present canyon area. Under this flow was a thermal area. Steam and gases weakened the rhyolite. Other lava flows blocked rivers until they overflowed and cut through the rhyolite. Then glaciers came and melted, deepening the canyon. The falls were caused by lava flow areas that didn't erode.
The Upper Falls is 109 ft. high. It can be seen from the Brink of the Upper Falls Trail and from Uncle Tom's Trail. The Lower Falls is 308 ft. high and can be seen from Lookout Point, Red Rock Point, Artist Point, Brink of the Lower Falls Trail, and from various points on the South Rim Trail.
Drive both the north and south rims for great views! If you're feeling like taking a tough hike, the trail to the brink of the lower falls is challenging. We didn't do the Uncle Tom's Trail, but got a good view of it from the brink of the upper falls. It consisted of stair going about half way into the canyon. If you have time for a really long hike, there are even trails running along the rims of the canyons on both sides. Many of the lookouts are right along the road, but if you're afraid of heights, you may not want to walk to the railing. The view from Artist Point was my favorite.
From journal Yellowstone, a Geological Wonder
This is one of the most acidic areas in the park. This makes it different from hot springs and geysers. The hydrogen sulfide gas deep in the earth at Mud Volcano is used by microorganisms and the resulting sulfuric acid then breaks down rock into wet clay mud. The steam and gases cause the volcanic action of the mud here. It was a lot more active in the days of the 1871 Hayden Expedition.
There is a very large bacteria matt by the parking lot. Hydrogen sulfide produces the rotten egg like smell which is quite strong here. There were a couple little noisy geysers going off while we were there---only shot up about a foot, but crackled and fizzled like a sparkler.
Dragon's mouth spring was an interesting noise maker, too. It is a hot spring that shoots sideways out of a cave opening. Hot water rising to the surface, hydrogen sulfide, carbon dioxide, and water vapor gases expanding create a pressure explosion in the cavern. The result is sloshing, belching, and steaming.
The walkway around this area is another short easy walk. Along with your sense of sight, this is a great place for your senses of smelling and hearing, too!