Geology
Most of the park is underlain by Triassic diabase, an igneous rock, and the many large, rounded boulders within the park are made of this material. Approximately 180 million years ago, the diabase intruded into older Triassic sedimentary rocks of the Gettysburg Formation, consisting of red sandstone and shale. Along the contacts of the diabase and sedimentary rocks, the molten diabase heated the sedimentary rocks to metamorphic rocks.
Read more about this topic: Gifford Pinchot State Park