East Sussex is a county in South East England on the English Channel coast. It is part of the anticline of the Weald called the South Downs. A range of chalk hills runs across the southern part of the county from west to east. The North Downs, which mirror the South Downs, are located in Kent. The north of the county has parallel valleys and ridges. The highest ridge is the Weald. The rocks are sedimentary, including chalk, sandstone and Wealden Clay. The sandstones contain significant reserves of shale oil, estimated 4.4 billion barrels of oil. But the oil extraction requires fracking which has been opposed by environmental groups.
The county has no karst, so there are few natural caves. The St. Clements Caves are originally natural caves in sandstone, but the current size is a result of sand mining. There are numerous sand mines, and other artificial caverns in the area.