Great Valley Section
Ridge and Valley Province


Great Valley Section showing geology and shaded relief

The Great Valley Section consists of a very broad lowland that lies south of Blue Mountain in southeastern Pennsylvania. The lowland has gently undulating hills eroded into shales and siltstones on the north side of the valley and a lower elevation flatter landscape developed on limestones and dolomites on the south side. Local relief is generally less than 100 feet, particularly in the carbonate area, but may be up to 300 feet in the shale area. Elevation ranges from 140 feet to 1,100 feet. Several large streams such as the Susquehanna and Schuylkill Rivers cut across the Great Valley. However, most of the well-defined drainage originates on the slopes of Blue Mountain and flows across the shales.

The lowland occurs in seven counties and extends from the Pennsylvania-Maryland border in Franklin County to the Delaware River in Northampton County. Routes along which the Section can be viewed include: Interstate 81 between Mary-land and its junction with Interstate 78, Interstate 78 from there to its junction with US Route 22 at Allentown, and US Route 22 from there to New Jersey; the Pennsylvania Turnpike (Interstate 76) from the Blue Mountain Tunnel to the Susquehanna River; US Route 422 from Hershey to its junction with US Route 222 near Reading and US Route 222 from there to Allentown; and US Route 30 east and west of Chambersburg.

Outstanding Geologic Scenic Features within the Section are: Big Spring, Big Spring (2), Boiling Springs, Huntsdale Hatchery Springs, Logan School Fossil Site, Reservoir Park Overlook, Spring Creek Springs, The Punchbowl, Blue Rocks Block Field, Schaefferstown Spring, Spitzenberg Hill, Swatara Gap Fossil Site, and Williams Quarry.

Colonel Denning, Memorial Lake, and Jacobsburg are State Parks in the Section.

There are no State Forest Natural Areas or Picnic Areas in the Section.