Larrys Creek is in a sandstone, limestone, and shale mountain region, with the source in the dissected Allegheny Plateau and the mouth in the Ridge-and-valley Appalachians. The southern part of the Larrys Creek watershed has sedimentary surface rocks from the Devonian period, with a large area from the Mississippian period in the north of the watershed and a small Pennsylvanian period region within this area. The Cogan House anticline runs north of and parallel to the upper part of the creek. Iron ore within the watershed was mined south of Salladasburg and along Canoe Run in the 19th century; there are also deposits on Puterbaugh Mountain.