 Both measurements give Joppenbergh a lower elevation than the highest point in the town of Rosendale, a peak of the Shawangunk Ridge.The bedrock underlying the mountain is composed of limestone and dolomite members of the Helderberg Group, laid during the Paleozoic era.Most of the Helderberg carbonates in Rosendale are located north of the Rondout Creek, and have given Rosendale a karst topography, resulting in "sink holes, disappearing streams, caves, and springs".