The rocks along Wissahickon Creek serve as wonderful examples of past and present geologic process.  The rocks themselves preserve evidence of moving continents, the closing of oceans and the formation of a great chain of mountains.  Today weathering and erosion work to expose these rocks that were once buried 25 km beneath Earth's surface and to shape the valley of Wissahickon Creek.  On this virtual tour photos and text keyed to a topographic map of the area will be used to explain the geology of park.  I hope though that you will have a chance to follow the trails of the park.  There is no way that to recreate the beauty of the valley and its forests, nor can you expect to understand the geology without seeing and holding the real rocks in your hands.

HOW TO PROCEED:
    Use the topographic map to follow the tour.  Each photograph is keyed to its location on the map.  By clicking your mouse on a number, you will open a page that describes the location and explains it geologic importance.  When you are finished with that page, either use the "BACK" button on your browser or click on "RETURN" to reopen the topographic map.