The ridge is primarily Shawangunk Conglomerate, a hard, silica-cemented sedimentary conglomerate of white quartz pebbles and sandstone that directly overlies the Martinsburg Formation, a thick sequence of turbidite deposits of dark gray shale and greywacke. The Martinsburg Formation was deposited in a deep ocean basin during the Ordovician (470 million years ago). The Shawangunk Conglomerate was deposited over the Martinsburg Formation in thick braided river deposits during the Silurian (about 420 million years ago); both sequences of sedimentary rock were subsequently deformed in a continental collision associated during the assembly of the Pangean supercontinent during the Permian (about 270 million years ago). This collision deformed strata within the ridge in a northward plunging series of asymmetric folds (e.g., anticlines and synclines) that are inclined gently westward. These same folds, involving strata that overlie the Shawangunk Conglomerate, are exposed north of Shawangunk Ridge in the Rosendale Natural Cement Region, where they can be directly examined in abandoned mines. Strata along the eastern margin of Shawangunk Ridge are truncated by erosion, resulting in the prominent cliffs characteristic of Shawangunk Ridge. The Shawangunk Conglomerate is very hard and resistant to weathering; whereas the underlying shale erodes relatively easily. Thus, the quartz conglomerate forms cliffs and talus slopes, particularly along the eastern margin of the ridge.