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York CWRT meeting for September 17

Mr. Jeri Jones of Spring Grove, distinguished York County geologist, author, and field guide
The York Civil War Round Table is pleased to announce the speaker for the September 17 meeting. Jeri Jones of Jones Geological Services will speak on the “Geology of the Gettysburg Military Park and How it Influenced the Battle.” The presentation will be at 7:00 p.m. in the auditorium of the York County Heritage Trust at 250 E. Market Street in downtown York. Parking and admission, as always, are free, and the public is welcome!

Vintage view of Cemetery Hill, one of the many distinct geological features of the Gettysburg Battlefield that Mr. Jones will discuss. In the foreground is part of Culp’s Hill.
The Gettysburg National Military Park is located within the Piedmont Gettysburg-Newark Section (from a geological perspective) and consists of rolling terrain. Our landscape is influenced by the underlying rocks. The battlefield is underlain with sedimentary rocks such as shale and sandstone which have been intruded by magma that eventually formed diabase. Where the magma baked the sedimentary rocks, a metamorhic rock known as hornfels has been formed.
Devil’s Den and Little Round Top are classic exposures of diabase and acted as barriers for defense during the Battle of gettysburg. Because only a thin soil forms over diabase, a typical act of trenching was not possible in much of the battlefield. We will answer such questions as, “Why is there a valley in the middle of Pickett’s Charge; What rocks are monuments made out of; Why was the First Day Railroad Cut there; and Did dinosaurs roam through this area some 200 million years ago when these rocks were forming?”
The PowerPoint program will give you a glance at the battlefield in a slightly different way that before.

About the speaker: Jeri Jones, a native of York, graduated from Catawba College in North Carolina with a degree in Geoarchaeology. He loves the study of geology of southeastern Pennsylvania, particularly the geological history and mining history. He has conducted research projects in the area for 30 years. Jeri has authored four books and produced three educational videos on local geloogy. He operates Jones Geological Services in Spring Grove, where he conducts educational geological tours for various schools. He also teaches continuing education courses at Harrisburg Community College and Penn State – York. He serves as a consulting geologist for Codorus Stone & Supply Company in Emigsville.