Shaping the Battlefield

Two hundred million years ago, geology set the stage for the Battle of Gettysburg. Tectonic plates shifted, creating the Gettysburg Formation, a compilation of sandstone, siltstone, and shale. Later, magma squeezed into spaces between rock layers and cooled, becoming diabase. Over time, softer materials were eroded by wind and water, shaping the landscape seen today. Weathered diabase stands as a prominent feature of this terrain. Formed over millions of years, the terrain determined road placements that funneled the armies into the Pennsylvania countryside, created the high ground, hampered troop movements, and offered strategic defensive positions.

Pennsylvania · United States