Hoodoos are tall, skinny rock spires that rise up from arid basins, such as the High Plateaus region of the Colorado Plateau and in the Badlands regions of the Northern Great Plains, according to the National Parks Service (NPS). But it's Bryce Canyon National Park in southwestern Utah that has more hoodoos than any other place in the world.
The unusual rock formations are often described as having a "totem pole-shaped body" and can be as tall as a person or a 10-story building, like Thor's Hammer (seen toward the left of this photo). The hoodoos in Bryce Canyon National Park formed about 40 to 60 million years ago. The NPS explains how they came to be: "The primary weathering force at Bryce Canyon is frost wedging. Here we experience over 200 freeze/thaw cycles each year. In the winter, melting snow, in the form of water, seeps into the cracks and freezes at night. When water freezes it expands by almost 10 percent, bit by bit prying open cracks, making them ever wider in the same way a pothole forms in a paved road."
Rain plays a big role in sculpting hoodoos, too. Hoodoos have layers of several different kinds of rock — one of them being limestone. The slightly acidic rainwater slowly dissolves the limestone, resulting in the rounded edges and lumpy silhouettes.