Devil's Tower Geology
http://www.nps.gov/deto/naturescience/geologicformations.htm

National Park Service (NPS)

This site from the National Park Service briefly addresses the geology of Devil's Tower. The evolution of various theories on the formation of the tower are discussed. A slide show of the emplacement of the tower is also available.

This resource is referenced here:

• Integrating Research and Education:Impacts on American Indian Lands:Pine Ridge: Geology and Physiography of Devils Tower

Subject: Geoscience:Geology:Igneous and Metamorphic Petrology, Geoscience:Geology
Resource Type: Scientific Resources:Overview/Reference Work
Topics: Time/Earth History
Theme: Teach the Earth:Course Topics:Petrology