Just south of Mammoth Hot Springs there is an area of enormous jumbled rocks flanking both sides of the road. The Hoodoos, as they are called, are not real hoodoos at all. The geologic term hoodoo refers to pinnacles that are created when hard erosion-resistant rock caps softer rock. Often bizarre shapes are formed as soft material, not protected by the caprock, erodes away.
This area known as the Hoodoos was probably given the name due to the odd shapes and angles of the huge boulders. What happened here is a land slide.
The rock was part of an ancient large hydrothermal system similar to the Mammoth Hot Spring Terraces. Sometime after the hot spring dried up, the travertine mineral sloughed off into large boulders. The rocks broke away from Terrace Mountain and tumbled down to rest in a jumbled up heap.
A large landslide, slipping on weak underlying Cretaceous shale, brought the colossal travertine stones and blocks of welded tuff down.
A short one-way loop road winds through the Hoodoos giving you a closer look and the same view as the stagecoach passengers of 1899. It looks as if a giant stomped through the area and toppled the rocks, leaving them strewn about in disarray. Even though the Hoodoos aren’t geologically hoodoos at all, they are fascinating all the same.