Volcanic Activity, Not Giant Bears, Created Enigmatic Devils Tower

Published: March 10, 2015

Source: Scott K. Johnson for Scientific American

Link: http://www.scientificamerican.com/article/volcanic-activity-not-giant-bears-created-enigmatic-devils-tower/

Science field: Geology, Sustainability

Summary

There are many hypotheses that have questioned the formation of the Devils Tower rock. Geologist Prokop Závada and some of his colleagues joined to the mystery because of a stout butte known as  in the Czech Republic that shares some similarities with Devils Tower. Bořeň is the product of a sudden type of volcano called a maar-diatreme, which blasts a crater in the land surface when a body of magma underground encounters groundwater. After the blast a flat dome of lava filled the crater. Erosion ate away at the edges of that dome until the innermost portion remained as an isolated butte.

There were two primary characteristics the researchers used to hone on the origins of Devils Tower: the shape of its distinctive columns and the alignment of magnetic minerals inside of them. They were to collect one rock sample to analyse its magnetic properties, and added these to existing measurements from 30 years ago. Near the base the tiny, needle-shaped magnetic minerals inside of the rock are generally close to vertical, the result of the direction the magma flowed before it solidified. Closer to the top of the formation, however, the orientation of those minerals becomes horizontal.

The vertical columns of Devils Tower, which splay outward near the bottom, match the pattern expected if the formation were indeed the plug in the neck of a funnel-shaped crater filled with a dome of erupted lava.

In a paper published in “Geosphere” Závada concluded that Devils Tower is a remnant of a coulee or low lava dome that was emplaced into a broad phreatomagmatic crater at the top of a maar-diatreme.

Glossary

-          Igneous: (of rocks) formed under intense heat, as from volcanos.

-          Scrap: a small piece or portion; fragment.

-          Butte: a single hill or mountain rising sharply above the surrounding flatter land.

-          Remnant: a remaining, usually small part or number of something; a small unsold or unused piece of fabric; a trace of something.

-          Dome: a roof or ceiling that is rounded or in the form of a part of a sphere.

-          Plug: a piece of wood or other material used to stop up or block a hole or opening, as in a pipe, etc.

Review

Devils Tower is a 49-million-year-old monolith of 390-meter-tall situated in Wyoming. The vertical lines that adorn its sides are the edges of roughly hexagonal columns of igneous rock, but how did the sky-scraping columns form? In that article we can see how many geologists have questioned the way the rock was formed, but any of them tried to discover it until Prokop Závada and his colleagues observed the similarities between this rock and the Bořeň. Apparently they do not have anything in common, but in fact, if you study both of their characteristics you will be able to understand how a strange rock was created.

Written by Alba Pazos