The geologic Tower formation theories
NPS Photo 1: A superimposed digital drawing of a cylinder-shaped stock over a photo of the Tower.
NPS Photo 2: A superimposed digital drawing of a mushroom cap-shaped laccolith over a photo of the Tower.
NPS Photo 3: A superimposed digital drawing of a volcanic plug and neck stretching above a photo of the Tower.
NPS Photo 4: A superimposed digital drawing of a maar-diatreme crater over a photo of the Tower.
Since the Tower stands alone in the landscape and the surrounding material has long since disappeared, scientists have multiple theories as to how the Tower formed. There are four major geologic theories, and all of them start in the same manner, with molten rock called magma pushing its way into Earth’s crust around 50 million years ago before cooling under the surface of the Earth.
The simplest geologic theory is that the Tower is a stock, or a small magmatic body intruded into the surrounding layers of rock, which was eventually eroded away to the Tower we see today.
A similar geologic theory is that the Tower is the remains of a laccolith, a large, mushroom-shaped mass of rock that pooled between other layers of rock in the Earth’s crust. The laccolith would have then experienced great amounts of erosion to eventually shape it into the Tower we see today.
The third, and one of the more commonly heard about geologic theories, is the volcanic plug theory. The Tower would be the inside remains of a volcano, the exterior having long since eroded away. The actual volcano portion would have been above the top of the Tower we see today.
The fourth, and most recently proposed geologic theory is the maar-diatreme theory. Magma would have risen through the layers of the Earth until it came into contact with groundwater. The groundwater would have turned to steam and caused a steam eruption forming a maar crater on the surface, which would have then filled with lava, eventually eroding into the Tower we see today.
All these theories involve the process of erosion shaping the Tower into its current form, but it is ironically that same erosion that makes it impossible to tell what the most accurate formation theory is, since all the evidence has long since eroded away.
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