Devils Tower

Photograph by Bates Littlehales

Devils Tower is a 264-meter (867-foot) rock formation in northeastern Wyoming.

Devils Tower is made of phonolite porphyry. Phonolite porphyry is an igneous rock, meaning it was formed as magma or lava cooled. As the magma that formed Devils Tower cooled, it condensed into columns. Most of the columns that make up Devils Tower are hexagonal (six-sided).

Although magma formed Devils Tower, it was probably never part of a volcano. Most geologists agree that Devils Tower is an igneous intrusion, a place where magma from the Earth's mantle welled up between chunks of sedimentary rock. Devils Tower was probably formed by the same forces that created the Rocky Mountains about 65 million years ago.

Devils Tower was not visible for millions of years. Only as water and wind slowly eroded the surrounding landscape did the igneous intrusion emerge.

Today, the landscape continues to erode, worn away by wind, precipitation, and the nearby Belle Fourche River. However, Devils Tower is eroding, too. The base of the formation is cluttered with scree—rubble, boulders, and fragments of columns that have broken off the tower.
Articles & Profiles
- National Park Service: Devils Tower National Monument—Geologic Formations
- National Geographic Travel: Top 10 Family-Friendly Hikes in the U.S. Parks
Books
- National Park Service: A Report on the Geology of Devils Tower National Monument
Images
- USGS: Devils Tower National Monument—A 3D Photographic Geology Tour
Worksheets & Handouts
- National Park Service: Devils Tower National Monument—Geologic Resource Evaluation Report

Term	Part of Speech	Definition	Encyclopedic Entry
emerge	Verb	to develop or come into view.
erode	Verb	to wear away.
hexagon	Noun	shape having six sides.
igneous intrusion	Noun	rock formation created by magma as it is pushed from the Earth's mantle into cracks or holes in the crust.
igneous rock	Noun	rock formed by the cooling of magma or lava.
landscape	Noun	the geographic features of a region.	Encyclopedic Entry: landscape
lava	Noun	molten rock, or magma, that erupts from volcanoes or fissures in the Earth's surface.
magma	Noun	molten, or partially melted, rock beneath the Earth's surface.	Encyclopedic Entry: magma
mantle	Noun	middle layer of the Earth, made of mostly solid rock.	Encyclopedic Entry: mantle
precipitation	Noun	all forms in which water falls to Earth from the atmosphere.	Encyclopedic Entry: precipitation
scree	Noun	accumulation of broken rocks, boulders, and other material at the base of cliffs or other tall rock formations.
sedimentary rock	Noun	rock formed from fragments of other rocks or the remains of plants or animals.
volcano	Noun	an opening in the Earth's crust, through which lava, ash, and gases erupt, and also the cone built by eruptions.	Encyclopedic Entry: volcano
wind	Noun	movement of air (from a high pressure zone to a low pressure zone) caused by the uneven heating of the Earth by the sun.

Credits

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Photographer

Bates Littlehales

Producer

Caryl-Sue, National Geographic Society

Last Updated

Jan. 10, 2012

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