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.

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.

Noun

rock formed by the cooling of magma or lava.

Noun

the geographic features of a region.

lava
Noun

molten rock, or magma, that erupts from volcanoes or fissures in the Earth's surface.

Noun

molten, or partially melted, rock beneath the Earth's surface.

Noun

middle layer of the Earth, made of mostly solid rock.

Noun

all forms in which water falls to Earth from the atmosphere.

scree
Noun

accumulation of broken rocks, boulders, and other material at the base of cliffs or other tall rock formations.

Noun

rock formed from fragments of other rocks or the remains of plants or animals.

Noun

an opening in the Earth's crust, through which lava, ash, and gases erupt, and also the cone built by eruptions.

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.