The ridge is widest () near the northern end and narrow in the middle (), with a maximum elevation of near Lake Maratanza. The ridge rises above a broad, high plain which stretches to the Hudson River to the east. On the west the low foothills of the Appalachian Mountains mingle with a low flat made by the Rondout Creek and Sandburgh Creek, the Basha Kill and various small kills, as well as the Neversink River and Delaware River at the southern end. These adjacent valleys are underlain by relatively weak sedimentary rock (e.g., sandstone, shale, limestone).