In geology, this is a tall spire of rock. Hoodoos usually form in dry areas such as deserts. These rock formations occur where many layers of soft rock — such as sandstone — are capped with a thin layer of harder rock. Over time, openings in the protective outer rock allows the softer rock beneath to wear away. But some of the thin cap of harder rock remains. And it can protect the rock that sits directly beneath it. Over eons, most of the rock disappears, leaving behind the occasional rocky tower, often with a larger cap on the top. Hoodoos can be anywhere from 1.5 to 45 meters (4.9 to 148 feet) tall.
In a sentence
Deserts in the Western United States host a lot of hoodoos, particularly in Utah’s Bryce Canyon National Park.