Central Pennsylvania Folded Rocks
May 27, 2004
During the Permian Period (290 to 248 million years ago), the continental mass of what is now Africa collided with the continental mass of Laurentia, now known as North America. In central Pennsylvania, the evidence of this compressive deformation can be seen in the major landscape features of the Valley and Ridge. This photo illustrates the intense folding and thrusting associated with this orogenic event (Alleghenian Orogeny) within the Tuscarora Formation (Lower Silurian) near Milroy, Pennsylvania. The entire height of the outcrop is approximately 50-60 feet (15-18 m).