The next time you drive through the mountains, look for these clues that tell scientists about how the landscape was formed so many years ago. Note that the layers of rock are not always horizontal. You may even see some seams of coal that have managed to miss being mined. Also note, as you take this drive in the mountains, that you are, in fact, driving in the mountains. Watching our rivers flow, and seeing the gentle ripples and occasional crest on a windy day, one can overlook the power of the currents beneath the surface.
Water is very efficient.
This erosion contoured Western Pennsylvania's valleys, a process that you can see at work when burbling rivulets turn to raging torrents after a heavy rain. This weathering has worked a long time to give the Appalachian Mountains their characteristic rounded shapes in contrast to the craggy, younger Rocky Mountains. Here in modern-day Pittsburgh, some people speak of a fourth river that runs underground, and feeds the fountain at Point State Park. This actually is more of an urban legend than a geological fact. All three of the rivers take their names from their old Native American names.