The rock formation and deformation processes described in Chapters 2 and 3 can be described as endogenic because they originate from within the Earth. When rocks are exposed at the Earth's surface by uplift and erosion, they are subject to exogenic processes that operate at or very near the Earth's surface. Exogenic processes include weathering and mass movement, which are described in this chapter, and fluvial, glacial, marine, karst, and aeolian exogenic processes, which are described in succeeding chapters. The processes that bring about the levelling or lowering of the surface of landmasses are collectively known as denudation. This chapter focuses on processes of weathering of rock material and mass wasting on slopes. Before we begin our examination of weathering and mass wasting, it is necessary to examine the links between endogenic processes described in Section I and exogenic processes that are the focus of the chapters in this section.