Devils Tower, Wyoming, USA
Devils Tower rises above eastern Wyoming, a mysterious and awesome presence for the original Indian inhabitants (and for the producer of "Close Encounters of the Third Kind," where the Tower had a leading role). Geologists find it mysterious today—it looks like the remains of an ancient intrusion of molten rock. It obviously cooled very slowly for the spectacular columnar jointing to develop in the rock. The Palisades near New York City and Devils Postpile, high in the California Sierra, are other examples. Because it cooled so slowly, it could not have been a volcanic neck. And besides, there are no lava flows or ash beds anywhere in the area.
The best guess is that it was part of a laccolith, a blister of magma that pushed between the layered sedimentary rocks deep underground, without ever reaching the surface. But the Tower, the part that's left, is pretty small for a laccolith—it seems to be the very last bit. The Devils Tower National Monument Web site has some more detail.
Oh yeah—Devil's Tower, with the apostrophe, is the wrong spelling. The U.S. Board on Geographic Names doesn't allow any official place name in America to have apostrophes. (Except for Martha's Vineyard, a ruling that required an act of Congress, and a very few others.)
