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Goblin Valley State Park is a state park of Utah, in the United States. The park features thousands of hoodoos, referred to locally as goblins, which are formations of mushroom-shaped rock pinnacles, some as tall as several yards (meters). The distinct shapes of these rocks result from an erosion-resistant layer of rock atop relatively softer sandstone. Goblin Valley State Park and Bryce Canyon National Park, also in Utah about 190 miles (310 km) to the southwest, contain some of the largest occurrences of hoodoos in the world.
The unusual stone shapes in Goblin Valley result from the weathering of Entrada sandstone. The Entrada consists of debris eroded from former highlands and redeposited on a former tidal flat of alternating layers of sandstone, siltstone, and shale. The rocks show evidence of being near the margins of an ancient sea with the ebb and flow of tides, tidal channels that directed currents back to the sea and coastal sand dunes.
Joint or fracture patterns within the Entrada sandstone beds created initial zones of weakness. The unweathered joints intersected to form sharp edges and corners with greater surface-area-to-volume ratios than the faces. As a result, the edges and corners weathered more quickly, producing the spherical-shaped ‘goblins’.
The Entrada sandstone from which the hoodoos developed was deposited in the Jurassic period around 170 million years ago.
Source: Wikipedia
https://en.wikipedia.org/wiki/Goblin_Valley_State_Park