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Intrusive and Extrusive Igneous Rocks

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Devil's Den

Devil’s Den

Credit: Hal Jeperson
Source: http://en.wikipedia.org/wiki/File:Devil%27s_Den_Gettysburg_1909.jpg
License: CC BY-NC 3.0

Geology had a big impact on the Battle of Gettysburg during the Civil War. On July 2, 1863, the 2nd day, the army that held those boulders won that fight. 

The Battle at Devil’s Den

  • At the start of the day, the Union Army held Devil’s Den and the nearby hills.
  • Confederate soldiers assaulted the Union regiments; fighting was brutal.
  • Confederate sharpshooters moved into Devil’s Den. They fired onto the Union soldiers atop nearby Little Round Top. Many Union soldiers dropped.
  • At the end of the day the Confederates still held Devil’s Den. This fight was one of their few successes that day.

Can You Apply It?

With the links below, learn more about geology and the Battle of Gettysburg. Then answer the following questions.

  1. How did the geology of Devil’s Den and the nearby hills help the Union army?
  2. Why was the geology of Devil’s Den not beneficial for the Union army?
  3. What types of rocks are found in the Gettysburg Formation? Which of the three main rock types do these rocks fit into?
  4. What type of rock is the Gettysburg Sill and the two dikes? How did it form?
  5. Why do the boulders stick out above ground?

Image Attributions

  1. [1]^ Credit: Hal Jeperson; Source: http://en.wikipedia.org/wiki/File:Devil%27s_Den_Gettysburg_1909.jpg; License: CC BY-NC 3.0

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