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Science & Nature • Geology

Devils Tower

Devils Tower is a prominent igneous rock formation in northeastern Wyoming, United States, and the central feature of Devils Tower National Monument.

By Ethan Anderson| Reviewed by Olivia Bennett, Standards & Fact-Checking Lead| Updated July 27, 2026|2 min read| Fact-checked

Devils Tower is a prominent igneous rock formation in northeastern Wyoming, United States, and the central feature of Devils Tower National Monument. It is known for its steep sides and distinctive columnar jointing, and it is the first U.S. national monument. Scientists generally describe it as an igneous intrusion formed as magma cooled underground and later became exposed by erosion.

Geology

Devils Tower is an igneous intrusion composed of phonolite porphyry. Its most distinctive feature is columnar jointing, which formed as the magma cooled and contracted.

Formation

The leading explanation is that magma rose into sedimentary rock and cooled below the surface, with later erosion exposing the tower. Some studies and hypotheses have debated whether it is best interpreted as a volcanic neck, laccolith, or related intrusive feature.

Physical characteristics

The tower rises about 386 m above the Belle Fourche River and stands as a highly visible landmark in northeastern Wyoming. Its fluted sides and polygonal columns are the result of cooling-related fracturing.

National monument status

Devils Tower was designated in 1906 as the first U.S. national monument. It remains protected and studied for both its scientific importance and cultural significance.

Key facts

  • Devils Tower is a steep-sided igneous body with spectacular vertical, hexagonal columns.
  • It rises about 1,267 feet above the Belle Fourche River and surrounding landscape.
  • The rock is commonly identified as phonolite porphyry.
  • Geologists agree it formed from magma intruding underground, though details of its origin remain debated.
  • It was protected as the first U.S. national monument in 1906.
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Canadian context

Devils Tower is relevant to Canadian readers as a major North American geologic landmark and protected area near the Canada–United States context of western geology and public land conservation.

Frequently asked questions

What is Devils Tower?
It is a large igneous rock formation in northeastern Wyoming, United States, and the main feature of Devils Tower National Monument.
How was Devils Tower formed?
Geologists generally say it formed when magma intruded underground, cooled, and later was exposed by erosion.
What rock is Devils Tower made of?
It is mainly composed of phonolite porphyry, an igneous rock.
Why does Devils Tower have columns?
The columns formed as cooling magma contracted and fractured into polygonal joints.
When was Devils Tower protected as a national monument?
It was protected in 1906 as the first U.S. national monument.
How tall is Devils Tower?
It rises about 1,267 feet (386 m) above the surrounding landscape.

References

  1. National Park Service — https://www.nps.gov/deto/learn/nature/tower-formation.htm
    Supports: Formation as magma buried beneath Earth’s surface; scientific study and protection context.
  2. U.S. Geological Survey — https://www.usgs.gov/geology-and-ecology-of-national-parks/devils-tower-national-monument
    Supports: First designated national monument; igneous intrusion and columnar jointing.
  3. National Park Service — https://www.nps.gov/articles/nps-geodiversity-atlas-devils-tower-national-monument-wyoming.htm
    Supports: Height above the Belle Fourche River, geologic setting, and rock classification.
  4. U.S. Geological Survey — https://pubs.usgs.gov/bul/1021i/report.pdf
    Supports: Geologic description of Devils Tower and intrusive origin.
  5. International Union of Geological Sciences — https://iugs-geoheritage.org/geoheritage_sites/devils-tower-mateo-tepe/
    Supports: Columnar jointing, rock type, cultural significance, and monument designation.