Continental drift is created at spreading centers, and this, along with subduction, drives the system of plates in a chaotic manner, resulting in continuous orogeny and areas of isostatic imbalance. The theory of plate tectonics explains all this, including the movement of the continents, better than Wegener's theory. Hans Stille and Leopold Kober opposed the idea of continental drift and worked on a "fixist" geosyncline model with Earth contraction playing a key role in the formation of orogens. Other geologists who opposed continental drift were Bailey Willis, Charles Schuchert, Rollin Chamberlin and Walther Bucher. In 1939 an international geological conference was held
Society for the Study of the Sudans UK Centre in Rutland Gate. More recently, international conferences have been convened in collaboration with the U.S.-based Sudan Studies Association (SSA) in Durham, England (2000), Washington DC (2003), Bergen, Norway (2006), Pretoria (2009) and Bonn (2012). Sandy Sanderson was the Society's second president, followed by the Sudanese novelist Tayeb Salih. The name was changed in 2016 to reflect the independence of South Sudan. Society for the Study of the Sudans UK The Society for the Study of the Sudans UK (SSSUK) is the largest UK-based professional association for scholars of Sudan and South Sudan. Founded in 1986, the Society's "overall aim