The Wissahickon Creek in northwest Philadelphia is a beautiful natural laboratory for exploring geologic processes including metamorphism, plate tectonics, and surficial geology.  This field guide is intended for the casual geologist, one with an interest rocks and earth history but without formal training.  I hope that you will be able to use it to increase your enjoyment of the park.  Please feel free to contact me ( ) with comments and questions.

    The guide is divided in two sections.  First is a tour of the area between Valley Green Inn and Rex Ave.  The second tours the area along forbidden drive near Bell's Mill Rd.  Valley Green can be approached from either Chestnut Hill (via Springfield Ave.) or Andora (by Wise's Mill Rd.).  Once you reach the Inn, go across the creek and follow the trail along the Wissahickon to the north.  You can return either by retracing your steps or following Forbidden Drive back to the Inn.  Expect the walk with stops to take between 1 and 2 hours.

    The topographic map of the area between Valley Green Inn and Rex Ave.

STOP 1 -- Wissahickon Schist                 STOP 2 -- More Schist               STOP 3 -- Evidence for mountain building          STOP3A -- Tributaries to the Wissahickon Creek       STOP 4 -- High temperature metamorphism and melting of the rock                 STOP 5 -- Amphibolites and their importance to the story                   STOP 6 -- More melting                    STOP 7 -- Age relationships between schist and granite                  STOP 8 -- Recent faulting along the Wissahickon                   STOP 9 -- Erosion and deposition in the Wissahickon