Rainwater enters the outcropping sandstones of Sideling Hill and collects in an aquifer. In this highway cut, the water runs out at the bottom of the fractured sandstone layers because it cannot go through the dense claystone below. Cuts like this often have continual water seeps or ice falls during winter. The ridge to the west is Town Hill, a syncline like Sideling Hill. What looks like an end to the hill is a cut eroded by a river that might have been bigger than today’s Potomac River. Town Hill extends tens of miles into Pennsylvania.

Photo: J. J. Prats

Union Township, Pennsylvania · USA