Landforms of York County

How many of you have taken a walk either in a developed area or in the quiet woods and stumbled over an interesting-looking rock?  Have you ever wondered how the rock was formed or how it got here?  Interesting rocks can be found anywhere and all it takes is to reach over and pick it up.  Every rock has a story to tell and this blog will tell these stories.

Each day everyone comes in contact with both geology and history.  This blog will explore some of the most fascinating locations in York County. This column will introduce stories about the origin of some interesting rocks, how we use natural resources and how we live with our geology.  Related topics are certainly welcome from the readers.

What better place to start than to introduce you to the general layout of the land and rocks in the county.

The highest point in York County is Stone Head, high atop South Mountain west of Dillsburg.  This exposure of quartzite is at an elevation of 1,371 feet above sea level.

The lowest point is along the Susquehanna River at the Mason-Dixon Line at an elevation of 200 feet.  That means that York County has a total relief of 1,171 feet.  Because of its magnificent view, some people regard Same Lewis State Park as one of the highest points.  Actually, this location and elevations in the Pigeon Hills near Hanover and the Hellam Hills in the eastern section of the county are just over 800 feet above sea level.

In the northern part of the county, the steep-sided hills of Roundtop (Ski) and Nell’s Hill are elevations of 1,355 and 1,330 feet respectively.  The rolling hills of southern York County are generally 800-900 feet in elevation with one ridge near Airville capping off just over 1,000 feet.

York County hosts igneous, sedimentary and metamorphic rocks.  These rocks range in age from about 600 million years old to as recent as 150 million years. The southern third of the county is composed of mostly metamorphic rocks that tell us of a vast ocean and several continental collisions.

The historic U.S. Route 30 lies within a limestone valley from near Thomasville eastward into Lancaster County. The limestone and surrounding rocks on the bordering ridges reflect a breakup and construction of an ancient continent.  Proof of a beach can be seen in the rocks in the now abandoned York Silica Sand Co. quarry behind the Harley-Davidson plant.

The northern third of the county is underlain with sedimentary and igneous rocks that are the youngest in our area.  These rocks tell us the amazing story of when York County was an Everglades swamp followed by the breakup of a large continent known as Pangaea. It is hard to realize that over a course of one billion years, York  has seen several episodes of continental collisions and breakups, an ocean environment, volcanic activity and dinosaurs walking through the mud of an ancient swamp.  York County has it all in the eyes of a geologist and offers many adventures that will be included here.

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