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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
|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.