Devil's Tower, Wyoming
Steven Dutch, Professor Emeritus, Natural and Applied Sciences, Universityof Wisconsin - Green Bay
In this more detailed map, Devil's Tower and the Missouri Buttes are red,elevations above 1400 meters are yellow, and elevations below 1400 meters aregreen.
Two features are significant. First is the clusterof small intrusions, the Missouri Buttes, only 5 kilometers northwest of Devil'sTower. They are about the same size and probably have very similar geology.Second, note that Devil's Tower lies below the surrounding countrysideand its summit is only a little above the mesa on which the Missouri Buttes sit.Thus Devil's Tower has been exposed by erosion, but it is not easy to see from adistance. It is visible from several places in the Belle Fourche valley alongI-90 east of Moorcroft. Actually, the Missouri Buttes, being higher and moreobvious, are the best guide to sighting Devil's Tower from a distance.
Above and below are more detailed maps of the tower. Note that it sits on anapproximately circular base about 1500 meters in diameter, surrounded, exceptfor a narrow neck, by valleys. Could this base represent the original extent ofthe intrusion?
Distant Views
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Devil's Tower (right) and the Missouri Buttes (left). |
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View northeast.
Below left: Missouri Buttes Below right: Devil's Tower |
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Local Stratigraphy
The Monument
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This view gives a nice picture of the tower and its surrounding
base.
Below: wild thangs. |
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Geology of the Tower
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View of the tower from the west at the visitor center |
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Jointing and fallen columns at the west base of the tower.
Below: fallen columns in the talus. The columns are not very regular at close range. |
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Close up of the phonolite that comprises the tower. |
The Base Trail
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Southwest side of the tower |
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Jointing at the base of the tower |
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South end of the tower |
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Detail of jointing. From bottom to top we see flaring columns, extremely regular columns, slightly undulose columns, and columns with horizontal jointing. |
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View south into the Belle Fourche valley. |
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Southeast side of the tower. |
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East side of the tower |
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East side of the tower |
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View east into the Belle Fourche valley. |
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East side of the tower |
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View northeast into the Belle Fourche valley. |
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Northwest side of the tower |
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The Belle Fourche River a few kilometers northeast of the tower. |
Origin of the Tower
The total lack of nearby volcanic rocks, the coarse porphyritic texture anduniformity of the phonolite, and the nearby Missouri Buttes all demolish theclassic idea of Devils Tower as a volcanic neck. It is clearly an intrusion.
The relationship of the tower to the local landscape suggests it was originallyburied and was exhumed by erosion of the Belle Fourche valley:
- The top of the tower is about at the same elevation as the Missouri Buttes.
- Like the Missouri Buttes, the top of the tower extends just a little above the top of the mesa surrounding the buttes
- The horizontal jointing at the top of the tower is typical of the upper levels of igneous bodies with columnar jointing and suggests the original top of the tower was not too far above its present level.
The elevated base on which the tower sits suggests the original extent of theintrusion may have been wider and that the intrusion may have shielded theunderlying sedimentary rocks during entrenchment of the Belle Fourche River.
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Created 7 April 2003, Last Update 06 June 2020