Sideling Hill syncline exposed on I-68 in Maryland. This large fold in Mississipian age strata resulted from the Permian collision of ancient North America with Africa about 230 million years ago. From here I head east and north on the superslab, detouring near the end to follow Route 209 through the Delaware Water Gap National Recreation Area.
All images copyright © 2013 F.W. Vollmer and may not be used without permission.