Within the area of extensive landslides shown in figure 2, a smaller area containing both thick and thin landslides was selected for detailed study (pi. 1). The trace of Delhi Pike extends east-west across the middle of the area and divides shallow landslides uphill from deep-seated landslides downhill. Subsurface conditions were investigated with borings and trenches. Instrumentation was installed in both shallow and deep slides to determine the geometry and water conditions and to obtain samples for laboratory testing.