Cumberland Township
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Cumberland Township - Devils Den is the classic exposure of the igneous rock known as diabase. Possibly forming 4-5 miles beneath the surface of the Earth, today diabase is at the surface because of its resistivity to weathering and erosion. Notice how the rock is in a rounded shape due to the weathering. This is called Balanced Rock. If you visit the site, walk in under the rock and look to the left where the top and side rock meets. There are two white marks on each rock that line up with each other. If you ever see these marks offset, one of these rocks has recently moved.
 
Cumberland Township - This is the CSX Railroad cut behind Lee’s Headquarters. This exposure is excellent to see what the rocks underlying the battlefield look like. The closest reddish-brown rocks are sandstone and shales belonging to what we call the Gettysburg Formation. The rock behind the gabion walls is diabase. The dark gray rock in the middle is known as hornfels. As magma intruded up through the shale and sandstones, the heat of the magma baked the rock. The cut is best viewed from the field behind Lee’s Headquarters.
 
Cumberland Township - This drawing completed by Roger Cuffey, retired professor of vertebrate paleontology from Pennsylvania State University shows the various rock slabs on the Confederate Ave bridge over Plum Run on the Gettysburg Battlefield. The rock was quarried from Trostle’s Quarry in Reading Township, Adams County. Please do not harm the foot prints with any tools. Only look and photograph.


 
Cumberland Township - An Atreipus foot print and hand print as seen on the Confederate Ave bridge on the Gettysburg National Military Park. This slab is located on the north side of the bridge.
 

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