This chapter examines ancient and modern geological and oceanographic processes relevant to that part of the Pacific Ocean lying offshore from the Chilean mainland. Initial overviews are presented of submarine geomorphology, plate tectonic background, Chilean physiography, oceanic circulation and present-day climate. These are followed by an examination of modern sedimentation, which looks at controls on marine productivity, the roles of plankton, organic matter and biogenic opal fluxes, calcareous and siliceous organisms, and the input of terrigenous sediment into the marine environment. These modern processes are then compared with past sedimentation patterns and palaeo-productivity, in a further attempt to better understand the driving forces behind ancient and modern environmental variability. The team of authors assembled for this chapter reflects a long-term cooperative effort between Chilean and German oceanographers. In 1991, the universities of Concepción, Austral de Chile, Católica de Valparaíso and del Mar instigated a scientific cooperative programme with the Department of Geosciences of the University of Bremen, Germany. Several projects funded by the German Ministry for Science and Education in the fields of biogeochemistry (JGOFS: Joint Global Ocean Flux Study - Chile) and palaeoceanography (CHIPAL: Spätquartäre Variationen der Paläoproduktivität im östlichen Südpazifik, SO-102 (Hebbeln et al. 1995); PUCK: Wechselwirkungen zwischen Produktivität und Umweltbedingungen am chilenischen Kontinentalhang, SO-156 (Hebbeln et al. 2001)), as well as Fondecyt-funded projects for studying biogeochemistry and palaeoceanographic processes, were conducted along the Chilean coast (Fondap I and II, Fondecyt no. 1010912 and no. 1040968). Key scientific goals of these projects include a better understanding of the El Niño-Southern Oscillation (ENSO) cycle and other large-scale phenomena, and how the Oxygen Minimum Zone and the Antarctic Intermediate Waters may influence, or be influenced by, global climate change.