Middle States Geographer, 1997,30:42-49 PHILADELPHIA'S WISSAHICKON VALLEY: ITS GEOLOGY AND GEOGRAPHY

ABSTRACT: The Wissahickon Vallry is a spectacular park system located in the city ofPhiladelphia. The wooded vallry is considered by many to be one ofthe most beautiful urban parks in the world. Its natural beauty is a creation of tectonic forces that occurred during the past 500 million years. Evidence of these forces can be found in the formation of the rocks of the Wissahickon, such as pegmatite, quartzite, schist, and gneiss. Additional evidence is provided by geological features, such as faults, joints, folds, and the rock formations emplaced by the action ofwater. The unique geology ofthe Wissahickon Valley has had an impact on geography, history and culture ofPhiladelphia over the years The water power provided by the creek brought industrialization to the area, the hills contributed to the loss ofthe historic Battle ofGermantown during the Revolutionary War, and the park provided a place ofquiet and beauty for Philadelphia's urban residents. Today, the geology and geography ofthe Wissahickon is a contributing factor to the park's deterioration through soil erosion. With its urban location, the park suffers from storm water runoff and over-use by a burgeoning population, both problems which are exacerbated by the park's landscape. In the northwest section of Philadelphia, GEOLOGY OF THE WISSAHICKON bordered by both urban and suburban neighborhoods, VALLEY there lies a little piece of wilderness called the Wissahickon Valley. City neighborhoods lie on three Natural Settin