On July, 5th, a field trip to Great Falls was conducted by Paul Lowman of the Geodynamics Branch. Starting at the Visitor Center on the C & O Canal, just south of Potomac, Maryland, the trip was mainly along the Billy Goat Trail, a 2 1/2 mile hike/climb around Bear Island.

The trail gives an outstanding look at the Lower Paleozoic Wissahickon Formation, a sequence of high grade schists widely distributed in the Maryland and Virginia Piedmont. A series of lamprophyre dikes exposed on the Maryland side of the Mather Gorge can be seen on the Virginia side, offset some 25 meters to the right along the fault that underlies the Mather Gorge. Farther south, following some vigorous climbing and scrambling, the group saw a classic exposure of graded bedding and soft sediment deformation in the Wissahickon, unusual in highly metamorphosed rock. Co-existing kyanite and sillimanite were seen, which with andalusite nearby define a pressure-temperature invariant point by the Gibbs Phase Rule. A series of metamorphosed gabbro sills was seen still farther south. The geology along the Billy Goat trail has generated several Ph.D. theses, one of them by George Fisher of Johns Hopkins University.

Gunther Kletetschka, with a strong background in metamorphic petrology and field experience in Labrador,accompanied the group, taking a series of digital pictures. The trip was highly productive and carried out without injury, something of an accomplishment in view of the rugged nature of the Billy Goat Trail.