Figure 1. A (above), Index map of the Eastern United States showing the location of the
field trip (star) near Great Falls of the Potomac River. Regional features
include the Fall Zone, separating the Piedmont and Coastal Plain provinces,
the Pleistocene glacial borders north of the Potomac River drainage basin.
B (right), Location map of the Potomac River in the vicinity of Great
Falls, showing the areas to be visited on Days 1 and 2 of this field